louis pasteur experiment on fermentation

Yeast and Fermentation

Louis Pasteur: The Father of Fermentation

Louis Pasteur was a French chemist and microbiologist celebrated for his research in vaccination s , pasteurization, and fermentation . His explorations led to extraordinary discoveries in the awareness of the causes and prevention of disease , fermentation , and germ theory.

Pasteur is known as one of the founders of modern bacteriology and is considered by many to be the “father of bacteriology and microbiology.” So, who was Louis Pasteur? And what were his extraordinary discoveries?  

Chance Favored the Prepared Pasteur’s Mind

Louis Pasteur was born on 27 December 1822 in Dole, France , the son of a tanner, Jean-Joseph Pasteur and of Jeanne-Etienne Roqui. In 1839, he enrolled at the Collège Royal at Besançon and earned his bachelor’s degree before his admission to the École Normale Supérieure. At the École Normale Supérieure, he studied chemistry, physics, and crystallography (the study of crystalline substances on the atomic scale). He completed his studies in 1847, presenting his two theses, one in chemistry and the other in physics .   

Pasteur served briefly as a professor of physics at the Dijon Lycée in 1848 before he became a professor of chemistry at the University of Strasbourg. In 1854, he was named dean of the new faculty of sciences at the University of Lille, where he began his studies on fermentation .  

Pasteur’s Battle Against Spontaneous Generation

Pasteur began his work on fermentation while working in the city of Lille in the north of France. He first set out to disprove the prevailing theory that fermentation was caused by decomposition , which he successfully refuted . He then demonstrated that it was yeast responsible for fermentation through the production of alcohol from sugar . Furthermore, Pasteur discovered that certain organisms, including yeasts, were able to live in the absence of air . He called them anaerobic organisms and famously stated, “fermentation is life without oxygen.” (1) By doing this he established the theory of the role of living microorganisms in fermentation . Around 1860, he demonstrated that microorganisms appear and grow not by spontaneous generation but because of the spores both in the air and on food . This also justified the theory that certain microbes are responsible for contagious diseases.  

This discovery helped Pasteur show that microorganisms were responsible for spoiling beverages such as milk, beer, and wine . In 1866, Pasteur created the process of what would later become known as “pasteurization” to counteract these spoiling effects. This process involved heating the liquids to a temperature between 60 and 100 °C for a certain amount of time. This heating process would, in turn, kill most of the bacteria and molds already present in the liquids , without altering their main qualities. Products which were pasteurized would in turn be less likely to spoil and have a longer shelf life .  Thanks to pasteurization, fresh milk, which normally goes bad after a few hours, could be stored for 1-2 weeks. This process was later applied to beer, wine, and other products .   

Pasteur further proved that when micro – organisms contaminated wine, lactic acid was produced, which would make the wine sour . (2) In 1861, Pasteur then identified that fewer sugars fermented per part of yeast when the yeast was exposed to air . (3) This lower rate of fermentation became known as the “Pasteur effect.” (4)  

Pasteur’s Work on Alcoholic Fermentation

In 1856, one of Pasteur’s students, whose father was a local wine manufacturer, approached him for advice on the problem of preventing beetroot alcohol from souring . This led Pasteur to begin his work on the optimization of the fermentation process.   

In the aftermath of France’s 1870 defeat in the Franco-Prussian War, Pasteur decided to use his research to help the French beer makers to become a true competitor to the German beer industry , which was booming. His research revealed that the process used at the time could lead to the yeast becoming contaminated by the environment in the brewery . If this happened beers could quickly turn sour and would not be able to be stored. Pasteur advocated making beer in a controlled environment with the least possible contact with air during fermentation and pasteurization in the bottle to stabilize the drink and prevent fermentation from continuing . Through this new process, French beer could be produced, stored, and shipped in large quantities without the risk of spoiling. This new process made French beer-brewing into a powerful industry. (5)  

Furthermore, the understanding of the fermentation phenomenon meant that the most suitable ferments could be cultivated and selected to seed fermented products . Beer yeast, Saccharomyces cerevisiae , was identified, and the cultivation of the pure strain began . Yeast became its own product and one that was industrially produced for the first time.   

The addition of specific yeast strains makes for faster, more stable, and more predictable fermentation . It also enables producers of beer, wine, bread, and other products to have more control over their product’s taste profiles.  

All of this was made possible by Pasteur’s work in understanding and revolutionizing the fermentation process.  

Pasteur’s Numerous Other Achievements

Pasteur’s work on microorganisms was also used to develop antisepsis and asepsis . Furthermore, during this time he also studied silkworm diseases and managed to eliminate Pébrine, or “pepper disease” which prevents larvae from rolling their silk fibers to make cocoons. He also discovered the anti-rabies vaccine and developed a vaccine against cholera in hens, anthrax, and diamond skin disease in pigs . Pasteur won international acclaim for his discovery of the anti-rabies vaccine and the Institute Pasteur was founded in 1888, to fight the rabies virus.  

His work on molecular asymmetry also had a major influence on the development of contemporary chemistry , with the appearance of stereochemistry, which focused on the spatial layout of atoms within molecules.  

Louis Pasteur died on 28 September 1895 at Marnes-la-Coquette, in Seine-et-Oise, leaving behind a wealth of research and discoveries that not only fostered innovative practical applications but continue to shape the way we look at the world around us today!

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Fermentation Science: History of Fermentation Science

• History of Fermentation Science
• Food Fermentation
• Liquid Fermentation I - Beer
• Liquid Fermentation II - Other

Rare Book Holdings at Linda Hall

• Études sur la bière : ses maladies, causes qui les provoquent, procédé pour la rendre inaltérable, avec une théorie nouvelle de la fermentation by M. L. Pasteur Call Number: QR151 .P296 1876
• Études sur la maladie des vers a soie : moyen pratique assuré de la combattre et d'en prévenir le retour by M. L. Pasteur Call Number: SF555 .P37 1870

History of the science

• Pasteur and modern science. by René Jules Dubos Call Number: Q143.P2 D82 1960
• Louis Pasteur, the story of his major discoveries by Jacques Nicolle Call Number: Q143.P2 N52 1961

• Pasteur's and Tyndall's study of spontaneous generation. by James Bryant Conant Call Number: QH325 .C6 Publication Date: 1953
• The Pasteur fermentation centennial, 1857-1957; a scientific symposium on the occasion of the one hundredth anniversary of the publication of Louis Pasteur's Mémoire sur la fermentation appelée lactique. by Chas. Pfizer & Co. Call Number: QP601 .P44 1957
• Studies on fermentation. The diseases of beer, their causes, and the means of preventing them by Louis Pasteur; Frank Faulkner; D. Constable Robb Call Number: QR151 .P3 1879 A translation, made with the author's sanction, of "Études sur la bière," with notes, index, and original illustrations, by Frank Faulkner

Early Fermentation

Fermentation is one of the oldest forms of food processing known today. Many of mankind's favorite food and beverages are products of fermentation, whether organically or induced, such as beer, wine, bread, sausages, and various sauces & marinades.

There are several different types of fermentations that can occur in food and liquids: alcoholic fermentation, acetic acid fermentation, and lactic acid fermentation.

• Alcoholic fermentation is possibly the most well known of the three types, its byproducts having been enjoyed by human civilization for millennia.
• Acetic acid fermentation is the process that begins where alcoholic fermentation ends. The most common result of this fermentation process is vinegar. 
• Lactic acid fermentation  is thought to be the oldest fermentation method, with fermented milk products being found in nearly every culture world-wide, and evidence of their consumption going back thousands of years. (see timeline)

Louis Pasteur: A Timeline

Louis Pasteur was a French physicist & chemist who's lifetime of discoveries changed science as we know it.  Making breakthroughs in fields such as crystallography, microbiology, fermentation science, and etiology, he contributed more in his lifetime than many before him.  Some of his prominent discoveries were: 

• his disproving of Spontaneous Generation and the discovery of microbes (his germ theory )
• the introduction of the Pasteurization Method
• the creation of vaccines & immunizations

The death of patient Jules Rouyer sparked a series of controversies that spanned the globe. Many scientists wanted to prove that Pasteur's method wasn't ready, or was completely false. However, Pasteur solidly argued & proved his case time & time again, keeping his vaccination method widely accepted.

Read the article on timetoast.com .

Fermentation Time Line

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• Scientific Biographies

Louis Pasteur

During the mid- to late 19th century, Pasteur demonstrated that microorganisms cause disease and discovered how to make vaccines from weakened, or attenuated, microbes. He developed the earliest vaccines against fowl cholera, anthrax, and rabies.

Louis Pasteur (1822–1895) is revered by his successors in the life sciences as well as by the general public. In fact, his name provided the basis for a household word— pasteurized .

His research, which showed that microorganisms cause both fermentation and disease, supported the germ theory of disease at a time when its validity was still being questioned. In his ongoing quest for disease treatments he created the first vaccines for fowl cholera; anthrax, a major livestock disease that in recent times has been used against humans in germ warfare; and the dreaded rabies.

Early Life and Education

Pasteur was born in Dole, France, the middle child of five in a family that had for generations been leather tanners. Young Pasteur’s gifts seemed to be more artistic than academic until near the end of his years in secondary school. Spurred by his mentors’ encouragement, he undertook rigorous studies to compensate for his academic shortcomings in order to prepare for the École Normale Supérieure, the famous teachers’ college in Paris. He earned his master’s degree there in 1845 and his doctorate in 1847.

Study of Optical Activity

While waiting for an appropriate appointment, Pasteur continued to work as a laboratory assistant at the École Normale. There he made further progress on the research he had begun for his doctoral dissertation—investigating the ability of certain crystals or solutions to rotate plane-polarized light clockwise or counterclockwise, that is, to exhibit “optical activity.” He was able to show that in many cases this activity related to the shape of the crystals of a compound.

He also reasoned that there was some special internal arrangement to the molecules of such a compound that twisted the light—an “asymmetric” arrangement. This hypothesis holds an important place in the early history of structural chemistry—the field of chemistry that studies the three-dimensional characteristics of molecules.

Fermentation and Pasteurization

Pasteur secured his academic credentials with scientific papers on this and related research and was then appointed in 1848 to the faculty of sciences in Strasbourg and in 1854 to the faculty in Lille. There he launched his studies on fermentation. Pasteur sided with the minority view among his contemporaries that each type of fermentation is carried out by a living microorganism.

At the time the majority believed that fermentation was spontaneously generated by a series of chemical reactions in which enzymes—themselves not yet securely identified with life—played a critical role.

In 1857 Pasteur returned to the École Normale as director of scientific studies. In the modest laboratory that he was permitted to establish there, he continued his study of fermentation and fought long, hard battles against the theory of spontaneous generation. Figuring prominently in early rounds of these debates were various applications of his pasteurization process, which he originally invented and patented (in 1865) to fight the “diseases” of wine.

He realized that these were caused by unwanted microorganisms that could be destroyed by heating wine to a temperature between 60° and 100°C. The process was later extended to all sorts of other spoilable substances, such as milk.

Germ Theory

At the same time Pasteur began his fermentation studies, he adopted a related view on the cause of diseases. He and a minority of other scientists believed that diseases arose from the activities of microorganisms—germ theory. Opponents believed that diseases, particularly major killer diseases, arose in the first instance from a weakness or imbalance in the internal state and quality of the afflicted individual.

In an early foray into the causes of particular diseases, in the 1860s, Pasteur was able to determine the cause of the devastating blight that had befallen the silkworms that were the basis for France’s then-important silk industry. Surprisingly, he found that the guilty parties were two microorganisms rather than one.

A New Laboratory

Pasteur did not, however, fully engage in studies of disease until the late 1870s, after several cataclysmic changes had rocked his life and that of the French nation. In 1868, in the middle of his silkworm studies, he suffered a stroke that partially paralyzed his left side. Soon thereafter, in 1870, France suffered a humiliating defeat at the hands of the Prussians, and Emperor Louis-Napoléon was overthrown. Nevertheless, Pasteur successfully concluded with the new government negotiations he had begun with the emperor.

The government agreed to build a new laboratory for him, to relieve him of administrative and teaching duties, and to grant him a pension and a special recompense in order to free his energies for studies of diseases.

Attenuating Microbes for Vaccines: Fowl Cholera and Anthrax

In his research campaign against disease Pasteur first worked on expanding what was known about anthrax, but his attention was quickly drawn to fowl cholera. This investigation led to his discovery of how to make vaccines by attenuating, or weakening, the microbe involved. Pasteur usually “refreshed” the laboratory cultures he was studying—in this case, fowl cholera—every few days; that is, he returned them to virulence by reintroducing them into laboratory chickens with the resulting onslaught of disease and the birds’ death.

Months into the experiments, Pasteur let cultures of fowl cholera stand idle while he went on vacation. When he returned and the same procedure was attempted, the chickens did not become diseased as before. Pasteur could easily have deduced that the culture was dead and could not be revived, but instead he was inspired to inoculate the experimental chickens with a virulent culture. Amazingly, the chickens survived and did not become diseased; they were protected by a microbe attenuated over time.

Realizing he had discovered a technique that could be extended to other diseases, Pasteur returned to his study of anthrax. Pasteur produced vaccines from weakened anthrax bacilli that could indeed protect sheep and other animals. In public demonstrations at Pouilly-le-Fort before crowds of observers, twenty-four sheep, one goat, and six cows were subjected to a two-part course of inoculations with the new vaccine, on May 5, 1881, and again on May 17. Meanwhile a control group of twenty-four sheep, one goat, and four cows remained unvaccinated.

On May 31 all the animals were inoculated with virulent anthrax bacilli, and two days later, on June 2, the crowd reassembled. Pasteur and his collaborators arrived to great applause. The effects of the vaccine were undeniable: the vaccinated animals were all alive. Of the control animals all the sheep were dead except three wobbly individuals who died by the end of the day, and the four unprotected cows were swollen and feverish. The single goat had expired too.

Rabies and the Beginnings of the Institut Pasteur

Pasteur then wanted to move into the more difficult area of human disease, in which ethical concerns weighed more heavily. He looked for a disease that afflicts both animals and humans so that most of his experiments could be done on animals, although here too he had strong reservations. Rabies, the disease he chose, had long terrified the populace, even though it was in fact quite rare in humans. Up to the time of Pasteur’s vaccine, a common treatment for a bite by a rabid animal had been cauterization with a red-hot iron in hopes of destroying the unknown cause of the disease, which almost always developed anyway after a typically long incubation period.

Rabies presented new obstacles to the development of a successful vaccine, primarily because the microorganism causing the disease could not be specifically identified; nor could it be cultured in vitro (in the laboratory and not in an animal). As with other infectious diseases, rabies could be injected into other species and attenuated. Attenuation of rabies was first achieved in monkeys and later in rabbits.

Meeting with success in protecting dogs, even those already bitten by a rabid animal, on July 6, 1885, Pasteur agreed with some reluctance to treat his first human patient, Joseph Meister, a nine-year-old who was otherwise doomed to a near-certain death. Success in this case and thousands of others convinced a grateful public throughout the world to make contributions to the Institut Pasteur.

Historian Bert Hansen discusses his book,  Picturing Medical Progress from Pasteur to Polio.

It was officially opened in 1888 and continues as one of the premier institutions of biomedical research in the world. Its tradition of discovering and producing vaccines is carried on today by the pharmaceutical company Sanofi Pasteur.

A Great Experimenter and Innovative Theorist

Pasteur’s career shows him to have been a great experimenter, far less concerned with the theory of disease and immune response than with dealing directly with diseases by creating new vaccines. Still it is possible to discern his notions on the more abstract topics. Early on he linked the immune response to the biological, especially nutritional, requirements of the microorganisms involved; that is, the microbe or the attenuated microbe in the vaccine depleted its food source during its first invasion, making the next onslaught difficult for the microbe.

Later he speculated that microbes could produce chemical substances toxic to themselves that circulated throughout the body, thus pointing to the use of toxins and antitoxins in vaccines. He lent support to another view by welcoming to the Institut Pasteur Élie Metchnikoff and his theory that “phagocytes” in the blood—white corpuscles—clear the body of foreign matter and are the prime agents of immunity.

Featured image: Portrait of Louis Pasteur , photograph of Louis Pasteur taken in 1886, reproduced in the 1911 biography   The Life of Louis Pasteur . Science History Institute

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Louis Pasteur: Between Myth and Reality

Jean-marc cavaillon.

1 National Research Agency (ANR), 75012 Paris, France

Sandra Legout

2 Centre de Ressources en Information Scientifique, Institut Pasteur, 75015 Paris, France; [email protected]

Associated Data

Not applicable.

Louis Pasteur is the most internationally known French scientist. He discovered molecular chirality, and he contributed to the understanding of the process of fermentation, helping brewers and winemakers to improve their beverages. He proposed a process, known as pasteurization, for the sterilization of wines. He established the germ theory of infectious diseases that allowed Joseph Lister to develop his antiseptic practice in surgery. He solved the problem of silkworm disease, although he had refuted the idea of Antoine Béchamp, who first considered it was a microbial infection. He created four vaccines (fowl cholera, anthrax, pig erysipelas, and rabies) in the paths of his precursors, Henri Toussaint (anthrax vaccine) and Pierre Victor Galtier (rabies vaccine). He generalized the word “vaccination” coined by Richard Dunning, Edward Jenner’s friend. Robert Koch, his most famous opponent, pointed out the great ambiguity of Pasteur’s approach to preparing his vaccines. Analysis of his laboratory notebooks has allowed historians to discern the differences between the legend built by his hagiographers and reality. In this review, we revisit his career, his undeniable achievements, and tell the truth about a hero who made every effort to build his own fame.

1. Introduction

In 2022, we are recognizing the 200-year anniversary of Louis Pasteur’s birth. Pasteur belongs to the pantheon of the most prestigious scientists, whose contributions allowed major improvements in the war against pathogens ( Table 1 ). The ongoing COVID-19 pandemic reminds humanity that this war remains contemporary. However, behind the great scientist there was a man with a huge ego who made every effort to build his fame, helped by the lay press and his hagiographers ( Figure 1 ). Among those, René Vallery-Radot [ 1 ], his son-in-law, and Émile Duclaux [ 2 ], his successor at the head of the Institut Pasteur, contributed to his legend, even if they had to tell fairy tales. Analysis of his correspondence and laboratory notebooks has allowed historians to decipher between myth and reality [ 3 , 4 , 5 , 6 ]. As such, a more realistic description of this character has emerged, such as that offered by Patrice Debré [ 7 ], qualifying him as unfair, arrogant, haughty, contemptuous, dogmatic, taciturn, individualist, authoritarian, careerist, flatterer, greedy, and ruthless with his opponents. This was illustrated when he was administrator and director of scientific studies at the prestigious “École Normale Supérieure” (ENS), which educates teachers and professors. His authoritarianism, his inflexible temperament, and his conflicting relationships with the students ended in the resignation of 73 students. This required the intervention of the Minister of Education and led to his resignation. Regarding his scientific contributions, Debré added: “ sometimes he gives the impression of merely checking the results described by others, then making them his own ”. One could add he was a misogynist. When Pasteur became professor and dean at the University of Lille (1854), he wrote to his rector: “ I have the honor of proposing to you that ladies no longer be admitted to the science courses of the faculty [...] I do not need to insist at length, Mr. Rector, on the inconveniences which may result from the presence of ladies at these lessons. I do not see any reason to admit them. If their number were to become large, they could cause an appreciable lowering of the level of teaching. Their presence is always a nuisance in the natural history class. ”

Left: Pasteur in the French Press seen as a lay saint ( Le Courrier Français , 4 April 1886); center: as an angel fighting rabies ( Le Don Quichotte , 13 March 1886); right: as a revered icon after his death ( Le Petit Journal , 13 October 1895). (© Institut Pasteur, Musée Pasteur).

Main contributions of Louis Pasteur.

The acquisition of knowledge is built on the shoulders of giants; however, many of these giants owe their notoriety to more obscure scientists who opened the furrows of knowledge and sowed the seeds which would hatch in other minds. Because Pasteur’s work was disruptive with nineteenth century knowledge, he faced many opponents, and history has forgotten those scientists whose only fault was to be right ahead of him.

2. From Molecular Chirality to Fermentation

Born in a family of tanners, Louis was the only boy with three sisters ( Table 2 ). He was a mediocre student who failed to pass his baccalaureate the first time, but he was an excellent pastellist. When he finally passed, he joined the ENS. Pasteur was invited by Antoine-Jérôme Balard (1802–1876), a prestigious chemist who had discovered bromine in 1826, to join his laboratory at ENS. Two other mentors supported Pasteur’s young career: Jean Baptiste Dumas (1800–1884), a professor of chemistry and member of the French Academy of Sciences, and Jean-Baptiste Biot (1774–1862), a professor of astronomy and physics and also a member of the French Academy of Sciences, who invented the polarimeter used by Pasteur for his first studies on the divergent diffraction of the light by tartaric and paratartaric acids. His studies on the optical activity and crystallography of these molecules allowed Pasteur to identify their molecular dissymmetry and their mirror-image nature. Pasteur was well ahead of his time and his discovery on molecular chirality catapulted the young Pasteur to the forefront of French research, recognizing what his eminent predecessors (J.-B. Biot, Frédéric-Hervé de la Provostaye (1812–1863), Wilhelm Gottlieb Hankel (1814–1899), and Eilhard Mitscherlich (1794–1863)) had missed [ 8 ]. For ten years, he pursued his research in chemistry and crystallography, founding stereochemistry.

Main steps of Louis Pasteur’s life and career.

While in Lille, Pasteur was contacted by beet alcohol producers who were facing difficulties in their process of fermentation. Studying this process would be the second main field of investigation of Pasteur. However, in contrast to the study of molecular chirality, Pasteur had many precursors. The fact that fermentation is part of the action of a living entity had been hypothesized since Antonie van Leeuwenhoek (1632–1723) observed yeast under his microscope in 1680. The link between these cells and the fermentation process was described in 1787 by Adamo Fabroni (1748–1816), in 1803 by Baron Louis Jacques Thénard (1777–1857), in 1836 by Theodor A.H. Schwann (1810–1882) ( Figure 2 ), in 1837 by Friedrich T. Kützing (1807–1893), in 1838 by Pierre Jean François Turpin (1775–1840) and Charles Cagniard de Latour (1777–1859), and finally in 1854 by Antoine Béchamp (1816–1908), who understood the process a few years before Pasteur, establishing the complementarity between yeast and a soluble substance he named “zymase” ( Figure 3 ).

The main predecessors recognized by Louis Pasteur (Spallanzani, Davaine, and Schwann) and his main supporters (Tyndall and Lister) (© Institut Pasteur, Musée Pasteur; © Wikipedia; © Collection of Pauls Stradiņš, Museum of History of Medicine, Riga, Latvia).

Louis Pasteur faced numerous precursors, opponents, and competitors. Some were wrong, but a few, particularly Hameau, Béchamp, Toussaint, Galtier, and Duboué, were right despite being unknown or poorly recognized by Louis Pasteur (© Wikipedia/© https://gw.geneanet.org accessed on 19 March 2022).

With regard to the first work of Pasteur on fermentation, his text published in 1858 [ 9 ] is at the very least ambiguous concerning his position on the concept of spontaneous generation: “ It is not necessary to already have lactic yeast to prepare it: it takes birth spontaneously, with as much ease as brewer’s yeast, whenever the conditions are favorable “ […] I use this word (spontaneous) as an expression of the fact, completely reserving the question of spontaneous generation. In contact with the common air, lactic yeast is born if the natural conditions of the environment and temperature are suitable .” In this text, he evaded the issue, hence this convoluted style. In 1856–1857, when he began to write this memoir, he had already been at work on fermentation for over a year. He was about to leave his position as dean of the faculty of Lille for the ENS. He apparently discussed this subject with his mentor Jean-Baptiste Biot, who dissuaded him from openly engaging in such a controversial subject. He knew he would need funding for his research and that he would apply for it through an Academy of Sciences Prize (Prix Montyon, 1859). He did not waver. This is what explains its lack of clarity; it does not engage yet. In addition, it was in 1860, when the Academy of Sciences proposed a competition (Alhumbert prize) to: “Try by well-made experiments to throw a new light on the question of spontaneous generations”, that he really launched into the battle and supported the role of living cells in the process of fermentation against the idea previously defended by Antoine Lavoisier (1743–1794) and arguing with his contemporary detractors, Justus Freiherr von Liebig (1803–1873), Friedrich Wöhler (1800–1882), and Claude Bernard (1813–1878). In a fight from beyond the grave, after Claude Bernard’s death, Pasteur, addressing his late opponent, published a book “ Critical examination of a posthumous writing by Claude Bernard on fermentation ” (1879), affirming urbi et orbi the importance of yeast and germs to obtain alcoholic fermentation.

Invited by beer and wine producers, bringing a microscope into a biochemistry laboratory, Pasteur identified pathogens that were responsible for different wine diseases. Thanks to pasteurization developed to allow the export of wines to England and his work on beer and wine, Pasteur became a recognized authority on industrial fermentation. The Whitebread breweries in Britain and Carlsberg in Denmark attribute their success to Pasteur’s visit after identifying that a microorganism was contaminating the fermentations required to make beer.

3. Fighting against Spontaneous Generation and Germ Theory

When he started his studies to refute spontaneous generation and initiated his germ theory, many demonstrations were already published by a large number of scientists ( Table 3 ). Indeed, Louis Pasteur was a great admirer of Lazzaro Spallanzani (1729–1799), recognizing his immense contribution when he first demonstrated the non-existence of spontaneous generation ( Figure 2 ). Pasteur was offered by Raphaël Bischoffsheim (1823–1906), banker, philanthropist, and deputy, a painting by Jules Édouard (1827–1878) representing Spallanzani, which hung in his large dining room. There is another scholar to whom Pasteur paid tribute by writing him in 1878: “ For twenty years now, I have been following some of the paths you have opened. As such, I claim the right and the duty to associate myself wholeheartedly with all those who will soon proclaim that you have well deserved science and to sign these few lines. One of your numerous and sympathetic disciples and admirers ” [ 10 ]. This is Theodor Schwann (1810–1882), a Berliner doctor who, in 1836, refined Spallanzani’s experiment by passing the air through a flame which enters in a flask containing an infusion sterilized by boiling. The same year, Franz Schulze (1815–1921), a German chemist and professor of anatomy in Rostock, Graz, and Berlin, enriched the experimental approach to demonstrate that air is a vector of germs. However, there were some awesome scientists who were fully ignored by Pasteur. Joseph Grancher (1843–1907), the physician who injected the first Pasteur rabies vaccine into humans, quoted some of them [ 11 ]: Jean Hameau (1779–1851) ( Figure 3 ) was a country doctor in the southwest of France who studied glanders, malaria, dysentery, yellow fever, smallpox, and cholera. In a prophetic book, entitled “ Studies on viruses ” (1847), he explained how germs are responsible for infectious diseases. Grancher wrote: “ if M Pasteur had known his work, he would have cited him as one of his precursors ”; Dr J. Hameau, in his study on viruses, talks about these viruses, their incubation and their multiplication, as a student of Pasteur would do nowadays. It is certainly a great accomplishment that this one! To have foreseen, divined, affirmed, with all the proofs which science of his time could offer him, a doctrine which, only fifty years later, and thanks to the genius of Pasteur, was to reign as absolute; it is, in my opinion, showing a penetrating sagacity. ” Jean Hameau died of a devastating sepsis in the arms of his son, himself a doctor. The epigraph to his book was: “ Everywhere life is in life and everywhere life devours life! ” It could not be a more appropriate definition of a microbe that carries away the human being that hosts it. Grancher also quoted Girolamo Fracastoro (1483–1553). This XVIth century doctor, who coined the word syphilis, anticipated the contagiousness of tuberculosis and considered that rabies was consecutive to the entrance of “seminaria” (germs) into the body: “ he was also an instinctive and brilliant precursor, also unknown to M. Pasteur, I am sure .

Some of the precursors who, before Louis Pasteur, proposed the germ theory and/or refuted the concept of spontaneous generation.

In his fight against the concept of spontaneous generation, Pasteur was helped by Balard, who conceived the experiments with the swan neck flasks, which were decisive in demonstrating that there are germs in the air [ 12 ]. Pasteur had to fight against some strong opponents of his germ theory who continued to defend spontaneous generation. Among those were, in France, Félix Archimède Pouchet (1800–1872) and his theory of heterogenesis [ 13 ] and Hermann Pidoux (1808–1882) and his theory of organic vitalism [ 14 ] and, in the UK, Lionel Beale (1828–1906) [ 15 ]. By contrast, John Tyndall (1820–1893), a famous Irish physicist ( Figure 2 ), was a great supporter of Pasteur’s theory of germs and published his own experiments on the presence of germs in the air [ 16 , 17 ]. A French catholic priest, Abbé Moigno (1804–1884), a great popularizer of science, gathered texts from Tyndall and Pasteur in a book on “ Organized microbes, their role in fermentation, putrefaction and contagion ”, [ 18 ]. The word “microbe” had been coined in 1878 by a French surgeon, Charles Sédillot (1804–1883), as a tribute of the works of Pasteur: “ Mr. Pasteur has demonstrated that microscopic organisms, widespread in the atmosphere, are the cause of the fermentations attributed to the air, which is only the vehicle and has none of their properties […] The names of these organizations are very numerous and will have to be described and, in part, reformed. The word microbe having the advantage of being shorter and of a more general meaning, and my illustrious friend M. Littré, the most competent linguist in France, having approved it, we adopt it […] ” [ 19 ]. However, Pasteur preferred to use the word microorganism. The word bacterium was coined in 1828 by Christian Gottfried Ehrenberg (1795–1876), a German naturalist, from the Greek βακτηριον, meaning “little stick”. The same six species of Vibrio described by Ehrenberg were recognized 35 years later by Pasteur as being the germs of putrefaction [ 20 ].

4. Fighting against the Silkworm Disease

Alexander von Humboldt (1769–1859), the great explorer, stated: “ The frequent sequence of reactions to an important discovery is first a denial of its veracity, then a denigration of its importance, and finally usurpation of credit for it ”. Such a statement fully fits with the contribution of Pasteur in the fight against silkworm disease. J.B. Dumas was minister of agriculture and trade and a senator in 1865 when he invited his former student to address the major threat that was facing the silkworm industry. Pasteur received subsidies from the government and spent five stays in Alès in the Cévennes. Pasteur initially admitted that he knew nothing about this topic. The famous entomologist Henri Fabre said: “ Ignoring caterpillar, cocoon, chrysalis, metamorphosis, Pasteur came to regenerate the silkworm. The ancient gymnasts presented themselves naked to the fight. Genius fighter against the scourge of the magnaneries, he also came to the battle naked, that is to say, without the simplest notions about the insect to get out of the peril. I was stunned; better than that I was amazed ” [ 21 ].

For two years, Pasteur denied that the disease (pebrin) could be due to a pathogen. However, Agostino Bassi (1773–1856), an Italian entomologist, had demonstrated as early as 1835 that another disease (muscardin) was caused by a fungus ( Beauveria bassiana ). In 1844, Bassi asserted the idea that not only animal (insect) but also human diseases are caused by other living microorganisms. On his side, A. Béchamp ( Figure 3 ), without official support, suggested as early as 6 June 1865 in front of the Central Agricultural Society of Hérault that the disease was due to a parasitic pathogen. On 25 September 1865, Pasteur communicated to the Academy of Sciences, opting for a spontaneous intrinsic blood disease [ 22 ]. The following year, Béchamp published: “ The pebrin, in my opinion, attacks the worm from the outside first, and the germs of the parasite come from the air. Sickness, in short, is not originally constitutional ” [ 23 , 24 ]. Béchamp’s diagnosis was supported by Édouard-Gérard Balbiani (1823–1899), an entomologist and embryologist who declared in 1866: “ The corpuscles that we observe in the disease described under the name of pebrin in silkworms are not anatomical elements […] but indeed psorospermia, that is to say parasitic plant species ” [ 25 ]. It was Désiré Gernez (1834–1910), working alongside Pasteur, and Franz von Leydig (1821–1908), a German zoologist, who had been contacted by Pasteur, who both convinced Pasteur of the real nature of disease. Gernez had worked as a physics associate/preparer in Pasteur’s laboratory at ENS from 1860 to 1864, and he joined Pasteur in Alès. The same as Béchamp and Balbiani, he concluded that the disease was parasitic. It was only in April–May 1867 that Pasteur sent a letter to Dumas finally acknowledging the parasitic origin of the disease [ 26 ]. Pasteur sent a letter in 1867 to the secretary of the agricultural committee, which overwhelmed Béchamp with discourteous contempt: “ Poor Mr. Béchamp is at this moment one of the most curious examples of the influence of preconceived ideas gradually turning into fixed ideas. All his statements are so biased that I wonder if he has ever observed more than ten silkworms in his life ” [ 27 ]. In his book written in 1870 on his studies of the diseases of silkworms, dedicated to the Empress Eugénie, to better capture all the glory and build his legend, Pasteur neither admitted his wanderings nor acknowledged the visionary works of Béchamp. The latter said: “ I am Pasteur’s forerunner, just as the stolen is the forerunner of the fortune of the happy and insolent thief who taunts and slanders him ” [ 28 ]. Unfortunately for Béchamp, his approach to treat the disease with fumigations of creosote was not fully appropriate while Pasteur’s technique of segregating the cocoons, an approach already proposed by Emilio Cornalia (1824–1882), an Italian naturalist, was successful. Thus, it was Pasteur who put an end to the epidemic and reaped all the praise. In fact, the success was very partial, as the production of cocoons, which reached 25,000 tons per year in 1850 and had collapsed to 5000 tons in 1865, never exceeded more than 8000 tons by the end of the 19th century.

Sadly for Béchamp, his concept of “microzyma”, which he subsequently developed, did not contribute to letting him enter the pantheon of heroes of microbiology. According to him, any animal or plant cell would be made up of small particles capable, under certain conditions, of evolving to form “microzymas”, small autonomous elements which would continue to live after the death of the cell from which they would come. After Pasteur’s death, Béchamp published a booklet entitled: “Louis Pasteur—His chemicophysiological and medical plagiarism—His statues” (1903). In this work, Béchamp published his various letters written in vain to restore the truth to the directors of the “ Petit Journal ” and “ La Liberté ”. He denounced “ The most brazen plagiarist of the nineteenth century and of all centuries: it is Pasteur ” and criticized the press “ for propagating the false legend which makes a famous plagiarist a great man ”. Reading Béchamp, one sympathizes with so much suffering illustrated by such harsh words: “ Pasteur, great man, the purest glory of the nineteenth century and undisputed scholar, not only he was not, but the pure truth is that he was the less genius, the most simplistic and the most superficial scientist of our time, at the same time the most plagiarist, the most false, and the biggest noise-maker of the nineteenth century ” and having shamelessly attributed the success to himself, Pasteur was able to further promote himself to Dr. Paul Bert (1833–1886), student of Claude Bernard and member of the National Assembly, where he obtained for Pasteur by a vote on 28 March 1874 a life pension of 12,000 gold francs per year, transformed on 13 July 1883 into a pension of 25,000 francs.

5. Identifying the Germs of the Infectious Diseases (1877–1881)

One of the main handicaps of Pasteur was having been educated as a physicist and a chemist and thus having ignored some key contributors in the field of medicine, infectious diseases, and physiology of inflammation. Furthermore, because he only spoke the French language, he missed many breakthrough publications from German scientists, leading him to make incorrect statements. For example, in 1878, he claimed [ 29 ]: “ For us currently, it would be the red blood cells that would be the pus cells from a simple transformation from the first into the second ”, ignoring the work of two of Rudolf Virchow’s (1821–1902) students, Julius Friedrich Cohnheim (1839–1884), who, eleven years earlier, had demonstrated that white blood cells cross blood vessels to become pus cells [ 30 ], and that of Julius Arnold (1835–1915), who in 1875 had illustrated the diapedesis of blood cells [ 31 ].

The competition between the German school led by Robert Koch (1843–1919) ( Figure 2 ) and that of Pasteur [ 32 ] was based on the identification of the germs responsible for some infectious diseases. Of course, the name of Koch is associated with discovery of the bacillus of tuberculosis and improperly to that of cholera, which was first identified by Filippo Pacini (1812–1883) in Florence (Italy) in 1854. The name “ Pasteurella ” was inappropriately coined by an Italian bacteriologist in 1887, Vittore Trevisan (1818–1897), while the germ responsible for the fowl cholera was first identified by two Italian scientists, Sebastiano Rivolta (1832–1893) in 1877 and Edoardo Perroncito (1847–1936) in 1878! In France, the first isolation of this bacterium was made by Henri Toussaint (1847–1890) in 1879 ( Figure 3 ), a medical doctor, a veterinarian, and a docteur ès-Sciences who provided Pasteur with this germ.

Let us speak of Joseph Grancher [ 11 ], the first French medical doctor with Isidore Strauss (1845–1896) who, thanks to Émile Roux (1853–1933), studied bacteriology with Pasteur under the supervision of Charles Chamberland (1851–1908): “ But already Germany had surpassed us in microbial techniques and Mr. Pasteur’s laboratory, faithful to cultures in liquid media, neglected the art of staining microbes and that of cultivating them on solid media. It was M. Babès (Victor Babeș (1854 in Vienna–1926 in Bucharest)) who, coming from Germany, introduced in France, in M. Cornil’s laboratory (Victor André Cornil (1837–1908)), the methods of staining microbes then used in M. Koch’s laboratory. And I believe I brought from Berlin, after a trip made with M. Brouardel (Paul Brouardel (1837–1906)) for Emersleben trichinosis (in November 1883), the first tubes of gelatinized blood serum. ” Indeed, thanks to the work of Angelina (Fanny) Hesse (1850–1934), her husband Walther Hesse (1846–1911), and Julius Richard Petri (1852–1921), Koch’s team had developed the agar–agar containing culture medium and the device known as the Petri dish. Grancher, with great objectivity rare in the close entourage of Pasteur, recognized the superiority of the experimental approach of the German school of bacteriology. The consequences were expressed in terms of discoveries: “ And while the studies on rabies and the search for its microbe continued on rue d’Ulm, while a few French doctors were beginning or better resuming their studies, Germany gave us almost in quick succession the important discoveries of the microbe of erysipelas, diphtheria, glanders, tetanus, pneumonia, this one recognized at the same time in France by Talamon (Charles Talamon (1850–1929) ” [ 33 ].

However, studying the boils of his colleague É. Duclaux and samples from a 12-year-old girl suffering from osteomyelitis, Pasteur identified Staphylococcus in 1880 [ 34 ] concomitantly with Alexander Ogston (1844–1929), a British surgeon who was studying the germs present in abscesses [ 35 ]. Ogston indicated that 917,775 cells/mm 3 were present in pus, which contained 2,121,070 micrococci/mm 3 . In 1882, Ogston coined the word Staphylococcus from ancient Greek staphyle, which means a bunch of grapes. Furthermore, concomitantly with the American George M. Steinberg (1838–1915) in 1881, Pasteur identified the bacteria first known as pneumococcus , then diplococcus pneumonia , and finally named Streptococcus pneumoniae [ 36 , 37 ].

5.1. Puerperal Fever

Pasteur investigated puerperal fever ten years after Victor Feltz (1835–1893) and Léon Coze (1819–1896), two physicians working in Strasbourg, demonstrated in 1869 the presence of a deadly bacterium ( Streptococcus ) in the blood of a patient who died of puerperal fever [ 38 ]. Starting in 1865 and for four years, the two Alsatian doctors established the presence of contaminating germs able to transmit death to rabbits injected with the blood of patients with typhoid fever, smallpox, pneumonia, erysipelas, and scarlet fever [ 39 ]. On 17 March 1879, Feltz, then in Nancy after the loss of Alsace in the 1870 war, republished a similar observation in the Comptes Rendus de l’Académie des Sciences, although this time he transmitted the death to a guinea pig [ 40 ]. Feltz called his observed bacteria Leptothrix puerperalis. The following day, Pasteur reported in the Bulletin de l’Académie de Médecine the presence of germs in the lochia, blood, and uterus from a patient who died of puerperal fever [ 41 ]. Pasteur did not perform experiments to transmit the disease to an animal but suggested washing the genital tract with diluted boric acid. Pasteur came into contact with Feltz and denied Feltz’ observation. He obtained some blood of Feltz’ patient, which he injected into one guinea pig while two others were injected with anthrax. He sent the animals by train to Nancy, where Feltz received the dying guinea pigs. Then, amazingly, Feltz, the medical doctor, accepted the diagnosis given by the scientist and he conceded that his patient after delivery had died of anthrax despite there being no case of anthrax in the area [ 42 ]! Most probably, both had observed Streptococci , a name coined by Theodor Billroth (1829–1894), as a combination of the ancient Greek streptos meaning twisted and kokkos meaning berry.

In the movie “ The story of Louis Pasteur ” (1936), directed by William Dieterle with Paul Muni playing Pasteur (a role for which he received the Oscar for best actor), following one death after puerperal fever, a document was created stating “ Wash your hands. Boil your instruments. Microbes cause disease and death to your patients ”, signed Louis Pasteur. In fact, Pasteur never mentioned that the hands of the obstetricians could transmit the disease, although Pasteur was very reluctant to shake hands and was himself regularly washing his hands. However, Pasteur and the scriptwriter ignored the statements of Alexander Gordon (1752–1799), who admitted in 1795 that he had transmitted diseases to women after delivery [ 43 ], and the major achievement of Ignaz Semmelweis (1818–1865), who demonstrated in 1847 that the hands of medical students, after performing autopsies, contaminated the parturients they visited [ 44 ]. In his Vienna hospital, Semmelweis advocated hand and nail washing with calcium hypochlorite, reducing the mortality from 16% to 0.85% [ 45 ].

5.2. Anthrax

The Bacillus anthracis was first observed in Germany by Aloys Pollender (1799–1879) in 1855 and Friedrich A. Brauell (1807–1882) in 1857. In France, in 1850, Pierre Rayer (1793–1867) was the first to demonstrate the contagiousness of the disease. However, the main achievement was accomplished by a precursor of Pasteur, Casimir J. Davaine (1812–1882) ( Figure 2 ). Jean Rostand (1894–1977), a famous writer and biologist, wrote: “ It is commonly believed in the public that it was Pasteur who discovered the role of microbes in the production of infectious diseases. In fact, this considerable discovery does not belong to him; it belongs to another French scientist: Davaine […] Who, the first, dared to affirm and knew how to demonstrate by the experimental method that a microscopic organism is the agent responsible for a disease ” [ 46 ]. Similarly, Jean Theodoridès (1926–1999), one of the most prestigious French historians of biological science wrote: “ The credit of demonstrating for the first time the pathogenic role of a bacterium in the human being and in domestic animals goes to the little-known French physician Casimir Davaine ” [ 47 ]. In 1863, Davaine observed the presence of bacteria in the blood of animals with anthrax and showed that the disease was communicable by infected blood [ 48 ]. Later, he reported that only live bacteria can transmit the disease [ 49 ]. Davaine was the first scientist to make a direct link between the presence of certain bacteria and an infection. He was well aware of the importance of his contribution: “ It has been a long time since doctors or naturalists theoretically admitted that contagious diseases, serious epidemic fevers, plague, etc., are determined by invisible animalcules or by ferments, but I am not aware of any clear demonstration to confirm this view ”. Indeed, Davaine was recognized by Pasteur to have been a major predecessor of his own work. In 1876, Koch was the first to publish photos of anthrax [ 50 ].

In 1877, Pasteur and Jules Joubert (1834–1910) reported [ 51 ] that the bacterium of anthrax could not develop when associated with other microorganisms: “ life prevents life ”. This was the very first report of a phenomenon named “antibiosis” by Jean Paul Vuillemin (1861–1932), mycologist and professor at the faculty of medicine in Nancy in 1889. The phenomenon would give rise years later to the discovery of the antibiotics. Finally, in 1880, Pasteur offered up an explanation for the natural contamination of cattle. He demonstrated that earthworms brought germs emanating from the carcasses of the dead sick animals to the surface, which had been buried in fields [ 52 ].

5.3. Cholera

In August 1883, a cholera epidemic broke out in Alexandria (Egypt). On August 15th, Pasteur sent his collaborators, Émile Roux, Isidore Strauss, Edmond Nocard (1850–1903), and Louis Thuillier (1856–1883), to isolate the germs and to reproduce the disease in animals. Not only did the mission fail, but Thuillier contracted cholera and died. Koch, on 24 August, also traveled to Alexandria to isolate the bacillus from the intestinal mucosa of dead people. He pursued his travel to Calcutta, India where another epidemic had broken out. On 7 January 1884, he sent a telegram informing Berlin that he finally isolated and cultured the bacillus. In 1893, Pasteur entrusted André Chantemesse (1851–1919) with a mission in Constantinople for another cholera epidemic. There, Chantemesse organized the fight against the epidemic with the construction of three disinfection stations. Later, Institut Pasteur sent Waldemar Haffkine (1860–1930), who trained in Metchnikoff’s laboratory, to fight against cholera epidemics in India thanks to a vaccine he had developed [ 53 ].

5.4. Plague

At the request of Institut Pasteur, Alexandre Yersin was sent to Hong Kong in 1894 to study the nature of the plague epidemic that was raging there. He was in competition with Shibasaburō Kitasato (1853–1931), a former trainee of Koch. When Kitasato was looking in blood samples, Yersin was luckier in studying buboes. On 20 June 1894, Yersin isolated the bacillus responsible for the disease, later named Yersinia pestis [ 54 ]. Back in France, he developed with Emile Roux, André Borrel, and Albert Calmette an anti-plague horse serum. While a large plague epidemic occurred in Guǎngzhōu (China) in 1896, Yersin went there to successfully offer his anti-plague serum. In the following years, Haffkine developed an anti-plague vaccine used in India to fight plague epidemics [ 53 ].

6. Pasteurization, Filtration and Sterilization

As previously mentioned, in his fight against the diseases of wines, Pasteur obtained a patent on 11 April 1865 that offered a means to get rid of the contaminating bacteria by heating the wines at 64 °C for 30 min. This process was later adapted to other products and named pasteurization. However, this approach had been previously proposed by Alfred de Vergnette de Lamotte (1806–1886), a gentleman winemaker (1846) of whom Pasteur denied the anteriority of his work. However, in fact, the very first approach had been reported in 1831 by Nicolas Appert (1749–1841), inventor of preserves who proposed the heating of wine in the 4th edition of his book [ 55 ] Then, Pasteur offered a scientific explanation to the empirical findings of his predecessors. Of note, it was Franz von Soxhlet (1848–1926) who first applied the process to milk.

In Pasteur’s laboratory, his close collaborator Charles Chamberland defended his doctoral thesis in 1879 on the origin and development of microorganisms. This was the starting point for his work on the sterilization of culture media that led him to design a disinfection oven that bears his name: the Chamberland autoclave. In 1884, to fight against the spread of typhoid fever raging in Paris, he developed a filter, designed from a porous porcelain of his invention, to eliminate microbes from drinking water. The instrument was named the Chamberland filter–Pasteur system and became very popular to provide safe drinking water. A Pasteur–Chamberland filter company was created in Dayton, Ohio, USA. They sold germ-proof filters to private homes, hotels, bars, and restaurants, offering many different designs. They advertised: “ This filter was invented in my laboratory, where its great usefulness is put to test every day. Knowing its full scientific and hygienic value, I wish it bears my name. Louis Pasteur ” [ 56 ].

Pasteur’s discoveries on germs allowed great advances in the practice of surgery. In 1865, Joseph Lister (1827–1912), a Scottish surgeon in Glasgow ( Figure 2 ), learned Louis Pasteur’s theory that microorganisms cause infection. Using phenol as an antiseptic, he reduced the mortality of amputee patients to 15% in four years, compared to 45–50% who died of sepsis previously. He is considered to be the founder of antiseptic medicine [ 57 , 58 ]. In 1870, Alphonse Guérin (1816–1895), a French surgeon, invented the wadded bandage and declared: “ I firmly believed that miasmas emanating from the pus of the wounded were the real cause of that dreadful disease to which I had had the pain of seeing the wounded succumb [...]. I then had the thought that the miasmas whose existence I had admitted because I could not otherwise explain the production of the purulent infection, and which were known to me only by their deleterious influence, might well be animated corpuscles that Pasteur had seen in the air [...] If the miasmas were ferments, I could protect the wounded against their fatal influence by filtering the air as Pasteur had done [...] I imagined then the wadded bandage and I had the satisfaction to see my forecasts being carried out ” [ 59 ].

On 27 December 1892, for Pasteur’s 70th birthday, the international scientific community celebrated Pasteur’s “jubilee”. The reception took place in the large amphitheater of the Sorbonne. In a painting painted ten years later, the artist Jean-André Rixens recalled this celebration displaying Lister precisely in the middle of the painting, shown going up a few steps to congratulate Pasteur ( Figure 4 ). In 1874, Just Lucas-Champonnière (1843–1913), after travelling to Scotland, introduced Lister’s antiseptic approach in France [ 60 ]. Similarly, Lewis Atterbury Stimson (1844–1917) attended a presentation of Pasteur in 1875 at the Academy of Medicine on spontaneous generation and the capacity of lime hyposulphite to instantly destroys all germs. Back in New York, in January 1876, he successfully completed the first amputation in the USA under completely aseptic conditions [ 61 ].

On 27 December 1892, for his 70th birthday, the international scientific community celebrated Pasteur’s “jubilé”. The reception took place in the great amphitheater of “la Sorbonne”. On the picture, one sees the president of France, Sadi Carnot, helping Pasteur to walk and Lister climbing a few steps to congratulate Pasteur. Oil on canvas by Jean-André Rixens (1902). © Institut Pasteur/Musée Pasteur.

7. Elaboration of Four Vaccines

7.1. fowl cholera.

Toussaint sent the heart of a guinea pig inoculated with the germ of chicken cholera to Pasteur in December 1878. After Pasteur had obtained the Pasteurella from Toussaint, he prepared a bacterial culture and developed his first vaccine against fowl cholera, which he reported in 1880 [ 62 ]. The legend told by Duclaux [ 2 ] is the following: a virulent culture of Pasteurella that was killing injected hens was left on the bench during Pasteur’s vacation. Back from vacation, Pasteur used this bacterial culture, which failed to kill the hens. He prepared a newly fresh virulent culture, injected it in the same hens, and these hens survived the lethal injection. From that observation, Pasteur elaborated that bacteria exposed to air or oxygen lose their virulence and can be used as a vaccine. Then, it could be claimed: “ In the fields of observation, chance favors only prepared minds ”. However, this event never happened. In 1878, Pasteur asked his son-in-law to never show his laboratory notebooks to anyone. However, in 1964, his grandson, Professor Louis Pasteur Vallery-Radot (1886–1970), donated the 152 notebooks to the French National Library, allowing the historians to explore legend and reality. The most accomplished investigation was carried out by Gerald L. Geison (1943–2001), who was awarded [ 3 ] with the William H. Welch Medal by the American Association for the History of Medicine for his book. The demystification of the great hero by Geison led to numerous laudatory comments [ 63 , 64 ]. The book was judged to be judicious, meticulous, and carefully argued [ 65 ]. Only the chapter on molecular chirality was severely criticized [ 66 ]. Jean Théodoridès wrote: “ This critical but objective work demystifies Pasteur, who became, partly on his own initiative, a hero of his time and a concentrate of all human virtues ” [ 67 ]. In addition, he recalled Auguste Lutaud (1847–1925), one of the most virulent Pasteur opponents: “ In France, one can be anarchist, communist, or nihilist, but not anti-Pasteurian. A simple scientific question has become a matter of patriotism ”. Théodoridès regretted that Geison did not address the story of silkworms nor the “Rouyer affair”.

Similar critical analyses have been previously proposed by Antonio Cadeddu [ 4 , 5 , 6 ] and Philippe Decourt (1902–1990) [ 27 ]. Considering the publications of Pasteur, his correspondence, the book of Pasteur’s nephew, Adrien Loir (1862–1941) [ 68 ], and the laboratory notebooks, they showed how much Pasteur sought for glory above all, to the detriment of his predecessors and his collaborators, rigging his experiments if necessary or distorting his results.

The analysis of notebook #88 reveals no text between July 1879 and November 1879: Pasteur was on vacation in Arbois, where he celebrated the wedding of his daughter Marie-Louise to René Valéry-Radot and afterward suffered from a gastroenteric disease. Texts from mid-November deal with anthrax, boils, and puerperal fever but not with the fowl cholera vaccine. On 14 January 1880, Pasteur wrote in his lab book: “ Hen’s germs: when should we take the microbe, so it could vaccinate?”, illustrating that there was not yet a clear understanding of the protective vaccine.

7.2. Anthrax (1881)

While the story of the fowl cholera vaccine was romanticized, Pasteur and his team were among the first after Edward Jenner to propose a new vaccine. However, the glory of developing the first vaccine against anthrax should not be attributed to Pasteur. In August 1880, Toussaint published his efforts to attenuate germs to obtain a protective vaccine in dogs and sheep [ 69 ]. He tried heating the bacteria, which was not successful; however, treating the germs with phenol led to a protective vaccine. In Vincennes, in August 1880, Toussaint organized a vaccination session on a total of 26 sheep on the farm of the Alfort Veterinary School in Vincennes. Twenty-two animals successfully resisted to the anthrax challenge [ 70 ].

The Pasteur team was groping for the development of an anti-anthrax vaccine. The main problem was Pasteur’s belief that it was exposure to air that produced attenuated germs that should be used for vaccinations. Chamberland and Roux tried various approaches with heated blood exposed or not to oxygen or attenuated by an antiseptic. About this last approach, Pasteur said to them: “ Me alive, you will not publish this, until you find the attenuation of the bacterium by oxygen. Look for it! ” [ 68 ]. However, Pasteur surprised his two acolytes when he announced in April 1881 that he had accepted the proposal of Charles-Paul-Marie Moreau, baron de La Rochette (1820–1889), president of the Society of Agriculture of Melun: “ We put at your disposal 60 sheeps. Ten will not undergo any treatment, 25 will be vaccinated, 25 will not be. After 12 new days, we will inoculate the virulent strain of the disease to the 25 sheeps and 25 others who did not receive a vaccine. Then we will see the results .” Taken aback, Chamberland and Roux were preoccupied and very busy actively pursuing the tests. The experiment was carried out on the farm of the veterinarian Joseph Hippolyte Rossignol (1837–1919) in Pouilly-Le-Fort in the presence of many personalities, including Eugène Tisserand (1816–1888), veterinarian and director at the Ministry of Agriculture, and a few journalists including one from The Times , who came from London specially to attend this unprecedented event. The vaccine was administered on 5 May 1881, as announced according to the protocol; however, two goats replaced two sheep, and eight cows, an ox, and a bull were added to the experiment, although the Pasteur team did not have any expertise with cattle. A boost was performed twelve days later. On 31 May, the very virulent strain was injected into all vaccinated and control animals. On June 2nd, all these people were back in Pouilly-Le-Fort. It was a huge success; the vaccinated sheep were in great shape, except for one ewe that died. It was identified that she was pregnant and had a stillborn fetus in her womb. The control animals were all dead or dying when the public rushed to the experiment site. All vaccinated and naïve cattle survived the inoculation. Baron de la Rochette and Dr. Rossignol hailed Pasteur’s great victory over anthrax. The phrase “ Fortune favors the daring ” has never been applied so well. Pasteur made an incredible bet, while his vaccine was still in its infancy, that no previous experiment had been conducted on this scale, and he descended into the arena, inviting the public to witness his experiments live. On 13 June 1881, Pasteur communicated his brilliant results to the Academy, failing to specify the nature of his vaccine [ 71 ], and for a good reason. In their race to produce an effective vaccine on time, Pasteur, Roux, and Chamberland ended up adopting Toussaint’s approach, namely, to attenuate the virulent germ, not by exposure to air as Pasteur will continue to imply but by exposing it to an antiseptic agent, in this case potassium dichromate.

Of course, the Pouilly-Le-Fort event caused a great sensation, and a statue was commissioned from the sculptor André d’Houdain and erected in 1897 in Melun. The bronze statue would eventually be melted down in 1943, the Vichy regime offering the occupier something to make cannons. However, a controversy arose between the professors of the Turin Veterinary School and their director, Domenico Vallada (1822–1888), to whom Pasteur had sent his vaccine against anthrax. Unfortunately, this vaccine was unable to protect Italian sheep. Pasteur estimated that the Italian veterinarians had made the mistake of inoculating for the test the blood of a corpse that had been dead of anthrax for more than twenty-four hours and that consequently germs other than those specific to anthrax had been injected. Vallada and his colleagues in Turin responded by publishing a text entitled “ On the scientific dogmatism of the illustrious Prof. Pasteur and the use that can be made of it ” (10 June 1883) [ 72 ]. They concluded their text to charge: “ We do not want to take away from our illustrious opponent the illusion of complete success which may have smiled upon him in this discussion, we likewise refrain from disturbing the sweet pleasure he experienced, when he provided new proof of the fault committed by the Turin Commission, however we believe that we are not straying from the truth, and not disrespecting him either, by expressing the opinion, that his complete success may in some way be compared to the historic victory of Pyrrhus ”. This was not the only failure of the vaccine. Nikolaï Gamaleïa (1859–1949), a medical doctor from Odessa who had come to Paris to be trained by the Pasteurians, studied the parameters that influenced the preparation of the anthrax vaccine and reported his own experiments carried out on more than 300 sheep and some dogs, rabbits, and rats [ 73 ]. He reported that certain preparations could kill sheep and established that the fever induced by the vaccine was a prerequisite for its effectiveness. Despite his efforts to master a vaccine that was complicated to prepare, during the summer of 1887, an anthrax vaccination organized by the Odessa bacteriological station resulted in the death of 80% of the vaccinated animals, i.e., 3549 sheep, at a cost of more of 40,000 rubles. The owner asked Elie Metchnikoff (then director of the bacteriological station) and Gamaleïa to reimburse him half the price and started a lawsuit. Of course, the popular press echoed this disaster. No doubt a major mistake had been made, in particular the large-scale use of a vaccine not previously tested. By contrast, Adrien Loir organized a successful anthrax vaccination of 400,000 sheep in Australia.

Pasteur reported his discoveries on the vaccine against fowl cholera and anthrax at the International Medical Congress in London (1881), where he stated: “ I have given the term vaccination a broad meaning. I hope science will dedicate it as a tribute to the merit and immense service rendered by one of England’s greatest men, your Jenner. What a joy for me to glorify that immortal name on the very soil of the noble and hospitable city of London ”. In fact, the word vaccination was coined in 1800 by Dr. Richard Dunning (1761–1851) [ 74 ], a founding member of the Plymouth Medical Society and friend and great supporter of Jenner, who had endorsed the word. As testimony of his admiration, Dunning named one of his sons Edward Jenner Dunning. Unfortunately, the child died at the age of ten months. Pasteur’s talk on the attenuation of viruses at the Fourth International Congress on Hygiene and Demography in Geneva (1882) ended with a vehement reply from Koch [ 75 ]: “ Pasteur is not a physician, and he cannot be expected to be able to comment accurately on pathological processes and symptoms of the disease.” […] ” The tactic followed by Mr. Pasteur is to communicate only what speaks in his favor about an experiment, and to ignore the facts which are unfavorable to him even when those are decisive for the purpose of the experiment. Such methods may be appropriate when it comes to advertising in business, but science must vigorously reject them. “ […] “It i s not only by the flawed methods, but also by the means of publishing his research, that Pasteur has provoked criticism. In industrial enterprises, it is permissible, and often even in commercial interests, to keep the process that led to the discovery a secret. But in science, it is another habit which is applied. Whoever appeals to faith and confidence of the scientific world has the duty to publish the methods that it follows, in such a way that everyone is able to verify the accuracy of the published results. M. Pasteur does not comply with this duty. Already in his publications on chicken cholera, Mr. Pasteur has long hidden his method of attenuating the virus and finally it was only at Colin’s (Gabriel-Constant Colin (1825–1896), Professor at the Maison Alfort veterinary school, Member of the Academy of Medicine) insistence that he decided to publicize his method. The same was repeated about the mitigation of the anthrax virus, because the communications that Mr. Pasteur has made so far on the preparation of the two vaccines are so imperfect that it is impossible without further information to repeat and examine its process ”. About Colin, Pasteur said: “ Only one path leads to the truth, a thousand lead to error, but it is always one of the latter that Mr. Colin chooses ” [ 76 ]. On his turn, Pasteur argued against Koch.

7.3. Pig Erysipelas

The development of Pasteur’s third vaccine was undoubtedly the least controversial. The originality of this work, however, is that Pasteur discreetly abandoned his approach attenuating germs by exposure to oxygen in the air [ 77 ]. In the summer of 1877, Achille Maucuer (1845–1923), a veterinarian based in Bollène (Vaucluse), wrote to Pasteur to challenge him on a pathology that was rampant in pig farms, swine erysipelas. Pasteur admitted he had never heard about that disease and asked Maucuer to provide him with some documents. In his letter (23 September 1877), Pasteur wrote a diatribe on the organization of research in his country that has a very particular resonance, as in recent years (2010–2020) France has dropped from fifth to ninth place in terms of scientific production in biology and medical sciences: “ If I could master my material resources for the research projects which impassion me, I would train young scientists who, under my direction, would undertake studies on all the contagious diseases of animals and men; but our poor France, always grappling with politics, remains ignorant of the great destinies of science. I would like to see the public authorities ceaselessly preoccupied with scientific interests; most often it is for immediate utility that they consider them. Witness, in the subject which occupies us, the standing committee of epizootics decreed in 1876 and which until now limited its work to the laws of sanitary police; without trying anything for the knowledge of the epizootics ” [ 78 ].

Pasteur wished to have access to the bacillus responsible for the disease. Maucuer sent a sick pig who died at Lyon Perrrache railway station. Nevertheless, it allowed the first inoculations. The germ, Erysipelothrix , was first isolated by Robert Koch in 1876–78 from septic mice that had been inoculated subcutaneously with the blood of rotten meat. In 1882, Friedrich Loeffler (1852–1915) observed a similar organism in the skin blood vessels of a pig that died of porcine erysipelas and published the description of the organism a few years later. Pasteur entrusted his assistant Louis Thuillier with the task of isolating the germ. The success of the young assistant was made possible by the development of a culture medium based on sterilized calf broth. Pasteur, Thuillier, and Loir went to Bollène in November 1882. The Maucuer couple hosted the Pasteurian delegation and—greatly honored by their presence—did their best to make their stay as pleasant as possible, even gastronomic. Pasteur reported that the quality of the dishes, in particular the truffled guinea fowl, was particularly appreciated. Pasteur quickly wrote to François de Mahy, Minister of Agriculture, to report on the progress of his work, emphasizing the economic impact of the problem. In the Rhône valley, around 20,000 animals had died. In Bollène and in the neighboring villages and castles, the Pasteurians had access to many animals for experimentation. After three weeks on site, Pasteur returned to Paris. The vaccine developed by Pasteur’s team consisted of erysipelas germs attenuated by passing them from rabbits to rabbits. Conversely, Pasteur found that successive passage through guinea pigs or pigeons increased their virulence. The details of the procedure, however, remained vague enough that no one could copy the preparation of the vaccine. Pasteur advised Maucuer: “ The vaccine would be considered of little value if we gave it for free. It will be delivered to you by Mr. Boutroux, 28 rue Vauquelin, at 0 fr 20 centimes per pig. You will charge your work as it fits you . However, I believe you would be wrong to charge a high price ” [ 78 ]. While some disappointments were reported with some animals that died after vaccination, overall, it was a huge success both in Vaucluse and in various regions of France. In 1892, Loir and Chamberland reported that the death rate was 1.07% for 57,900 vaccinated animals. Pasteur obtained from the Minister of Agriculture that Maucuer would be awarded the Legion of Honor. Since then, an Achille Maucuer Avenue has existed in Bollène, and of course in this same town, a bronze bust of Pasteur was inaugurated in 1924. As in Melun, in 1943 the bust was melted down under the Vichy regime. Rebuilt in 1945, the base and the bust regained their place in the city center of Bollène in 2017.

7.4. Rabies

Pasteur’s fourth vaccine was undoubtedly the one that contributed the most to his fame, but it was also a hot topic of contradictory debate. What was the motivation that led Pasteur to work on rabies? Pasteur was a hero among breeders and veterinarians, but tackling a human disease would have much more prestige, more repercussions in the medical world, and in the general population. The choice of rabies may be intriguing because it was an epiphenomenon compared to the mortality resulting from the other infectious diseases that were rife at the time. No doubt he wanted to avoid German competition, which was on many fronts but not that of rabies. What characterizes rabies is the long delay between the bite (assumed to have been given by a rabid animal) and the onset of the disease, at least if the bite was on the extremities of a limb. This delay allowed Pasteur to carry out his inoculations and hope for the establishment of immune protection before the onset of the disease.

Once again, there are forgotten precursors. Pierre Victor Galtier (1846–1908) was a professor at the veterinarian school of Lyon holding the chair of pathology of infectious diseases ( Figure 3 ). In 1879, he demonstrated the transmissibility of rabies from dogs to rabbits [ 79 ]. This key information was then used by Pasteur: rabbits could be a source of rabies virus, and the rabbits used for tests developed the disease very quickly. Roux improved the model by proposing an intracerebral inoculation. On 1 August 1881, Galtier reported to the Academy of Sciences the success of his rabies vaccination [ 80 ]: “ I injected rabies saliva into the chinstrap of the sheep seven times, without ever getting rabies; one of my test subjects has since been inoculated with rabid dog slime, and for over four months after this inoculation, the animal has always been well; it seems to have acquired immunity. I inoculated it again two weeks ago by injecting it eight cubic centimeters of rabies saliva into the peritoneum, it is still doing well ”. In total, he injected the rabies virus into the blood stream of nine sheep and one goat. He then injected the deadly virus into these animals and ten control animals. The ten vaccinated animals survived, and the ten control animals perished. In 1886, Galtier published a work entitled: “ Rabies considered in animals and in humans from the point of view of its characteristics and its prophylaxis ”. Even though a bust of Pierre Victor Galtier by Louis Prost can be seen at the veterinary school in Lyon, very few remember his original work.

In addition to Galtier, we should also mention among the precursors Pierre-Henri Duboué (1834–1889), a doctor trained in Paris and member of the Academy of Medicine, who practiced in Pau ( Figure 3 ). On 12 January 1881, he sent his book to Pasteur [ 81 ] in which he reported his discovery that the progression of the rabies virus takes place through the peripheral nerve fibers to the central nervous system and not through the blood, at a time when Pasteur was still looking for the viruses in the bloodstream. In 1887, Duboué wrote a new book in which he stated [ 82 ]: “ I come with this work, to defend my unjustly unrecognized rights, on the subject of the progresses made in recent years on the great question of rabies, progresses which I can strongly affirm to have been prepared by my own research ”. Decidedly, it was not good to be in the shadow of Pasteur’s work. Later, he added: “ To make it clear the full extent of the denial of justice to me contained in Pasteur’s communication, I must indicate here the reason which gave a whole new direction to the researches of M. Pasteur.” […] “No civet without hare […] Similarly, no preventive treatment possible with attenuated viruses, without the prior culture of the rabies virus, and no culture of the latter, without knowledge of the tissues or organs where this virus resides ” wrote appropriately Duboué.

Pasteur experimented with his rabies vaccine in humans before he had accumulated sufficient evidence of the efficacy and safety of his vaccine. Ethics in Pasteur’s time were obviously not as scrupulous as that of the twenty-first century, as illustrated by his request in 1884 to the Emperor of Brazil to be allowed to test his vaccine on prisoners in exchange for their freedom [ 83 ]. In his book and after examining Pasteur’s notebooks, Geison makes a damning observation [ 3 ]. Before the first attempts on humans, between August 1884 and May 1885, experiments involved 26 dogs bitten by rabid dogs with three different vaccine approaches. The overall success rate was 62%. However, none of them correspond to the one used on Joseph Meister. This is undoubtedly one of the reasons why his most loyal collaborator, Dr Roux, refused to test the vaccine in humans on which he himself had been working, and it was Joseph Grancher who performed the injections. As a source of attenuated viruses, it was Roux’s idea to dry out the spinal cords of rabbits that had succumbed to rabies, hung in vials, while Pasteur had the idea to add potash to accelerate the drying. Pasteur’s laboratory notebooks reveal that Joseph Meister was not the first human to be treated with Pasteur’s rabies vaccine. The very first rabies vaccination was carried out on 2 May 1885 on a patient of Dr. Georges Dujardin-Beaumetz (1833–1895), member of the Academy of Medicine, at Necker hospital, named Mr. Girard (61 years old), who had been bitten on the knee by a rabid animal. The treatment was initiated with two injections twelve hours apart. However, the treatment was stopped by the hospital authorities who had consulted the Ministry of Public Health. On May 3rd, Girard’s conditions deteriorated with tremors that lasted three days. On May 7th, the patient was much better, and a fortnight later, the patient was discharged from the hospital. Doubt persisted as to the nature of this first patient’s illness. The second injection took place on 22 June 1885 at the Saint-Denis hospital, where an eleven-year-old girl, Julie-Antoinette Poughon, was vaccinated. Unfortunately, she died the next day, suggesting that the administration of the vaccine was too late. The best-known inoculation took place on 6 July 1885 on young Joseph Meister (1876–1940), aged 9, who came with his mother from Alsace. Administration of the vaccine, as defined by Pasteur, consisted of a succession of inoculations with the desiccated spinal cords of rabid rabbits by injecting increasingly virulent virus preparations until the fully active virus was injected. The experimental approach with parched spinal cord was initially started on 28 May and 3 June in 20 dogs and repeated on 25 and 27 June in 20 new dogs. This is to say whether on July 6th Pasteur had little data to ensure the efficacy and safety of his protocol. Pasteur notes in his notebook: production of the refractory state on a child very dangerously bitten by a rabid dog. Pasteur is aware of the dangerousness of his treatment: “ Joseph Meister therefore escaped not only the rage caused by the bites, but also the one I injected into him to control immunity ” [ 84 ].

The second vaccination was carried out on 20 October 1885 in a young 15-year-old shepherd, Jean-Baptiste Jupille (1869–1923). Meister, like Jupille, was infinitely grateful and became a guardian of the Institut Pasteur. Meister committed suicide when the Nazi army entered Paris. Another thing the two young people had in common was that there was a lack of evidence that they were actually bitten by rabid dogs. The dog that bit Meister was killed and autopsied; finding wood debris in his stomach was the only evidence that he would have had rabies. Yet, Michel Peter (1824–1893), member of the Academy of Medicine, reminded his colleagues: “ In the past, you remember, any dog in whose stomach one found foreign bodies: wood, straw, etc., was famous enraged; this proof is abandoned ” [ 85 ]. As for Jupille, it was not the dog who attacked the child but the child who attacked the dog by rushing towards him with his whip (which Pasteur knew). The animal defended itself and bit young Jupille’s hand. The latter tied the dog’s mouth with the rope of his whip and threw it into the river. The statue which stands in the grounds of the Institut Pasteur, where one sees the young Jupille fighting with a dog to protect his little comrades from the attack of a mad dog, helped to propagate the legend.

During the course of Jupille’s vaccination, Grancher pricked himself in the thigh with the needle of a syringe filled up with four-day-old spinal cord, that is to say containing virulent virus. A full vaccination process was then necessary for Grancher. Pasteur asked to be inoculated as well. Grancher refused, as did Loir, and in doing so disobeyed Pasteur for the first time. Then, Adrien Loir and Eugène Viala (1858–1926), a laboratory technician, got vaccinated as well [ 68 ].

On 26 October 1885, Pasteur presented his successes to the Academy of Sciences and its president, Henri Bouley (1814–1885), which was hailed a memorable moment in the history of medicine and forever glorious in French science. The next day, Pasteur presented the same results to the Academy of Medicine, hailed once again as a most memorable moment in the history of the conquests of science and in the annals of the Academy. The international impact was arguably as high as Pasteur had hoped. As early as the fall/winter of 1885, people came from far away to receive the life-saving treatment: from Russia, the nineteen muzhiks of Smolensk (fifteen of whom were rescued), who had been welcomed at the railway station by the Baron Arthur Pavlovitch de Mohrenheim, ambassador of Russia in Paris, or from America, the four boys from New Jersey. Robert M. McLane (1815–1898), ambassador of USA, offered a banquet to glorify Pasteur. These successes played an essential role in the creation of the Institut Pasteur, inaugurated on 14 November 1888 [ 86 ].

Léon Perdrix (1859–1917), a former student at ENS and associate preparer in Pasteur’s laboratory, published the results of the first years of vaccination [ 87 ]: from 1886 to 1889, 7893 people (including 15.9% foreigners) were treated, and the mortality was only 0.67%. Admittedly, the mortality from rabies was greater than 98%, but how many of the people treated had actually had rabies? Decourt says he has verified and estimated the number of cases of rabies in France during the years 1850 to 1876 at 28.5 cases per year. It emerged that a number of people were treated even though they had not been bitten by rabid dogs [ 27 ].

Despite the aura of Louis Pasteur’s vaccination against rabies, a few clouds gathered in the sky of the glorious hero. There is first the “Jules Rouyer affair”, when a ten-year-old boy was bitten on the arm by an unknown dog through his overcoat on 8 October 1886. Pasteur was on vacation in Bordighera on the Italian Riviera, and it was Andrien Loir who took over the vaccination. Rabies inoculations began on 20 October, carried out daily for twelve days. Sadly, the child died on 26 November. Due to the father, Édouard Rouyer, having lodged a complaint, an autopsy was performed in Loir’s presence by Brouardel and Grancher, who took the child’s medulla oblongata and sent it to Roux so that he could inoculate two rabbits. The result was not long to come, and both rabbits quickly died of paralytic rabies. Roux and Brouardel perjured themselves in court, claiming that the rabbit tests had been negative and that the child had not died of rabies but of a uremic attack [ 7 ]. By doing so, they felt they were acting for the benefit of mankind by saving vaccination. The risk/benefit ratio of such a revelation was recognized by Roux himself. However, not all were convinced, in particular Michel Peter, who considered that the child had indeed died of rabies. He regularly opposed Pasteur, especially since he also witnessed another case of death despite (or because?) of the vaccine, that of a young man of twenty, called Réveillac, who died of rabies after receiving treatment. Peter declared: “ To amplify the benefits of his method and to mask its failures, Mr. Pasteur has an interest in making the annual mortality rate from rabies in France believed to be higher. But these are not the interests of the truth. Do we want to know, for example, how many individuals in 25 years have died of rabies in Dunkerque? He died of it: one… And do we want to know how many died in this city in a year, since the application of the Pasteurian method? He died: one ”. However, Pasteur considered Peter’s words null and void. Among the failures, let us also note the case of Hayes St Leger, fourth Viscount Doneraile (1818–1887). In Ireland at the time of the last outbreak of rabies, Lord Doneraile and his coachman Robert Barrer were both bitten by a rabid fox on 13 January 1887. Lord Doneraile suffered severe, multiple, and deep bites on both hands. They went to Paris to receive the full treatments between 24 January and 21 February. Unfortunately, Lord Doneraile finally died of rabies on 26 August 1887 as a result of fox rabies or the inoculation during the treatment. Pasteur dealt with another opponent, Anton von Frisch (1849–1917), an Austrian urologist who had nevertheless come to train with him. In 1887, he published a work entitled “ The treatment of rabies disease: an experimental critique of Pasteur’s method ”, in which he questioned the reliability and relevance of Pasteur’s vaccine approach.

The discovery that rabies was due to a virus was made in 1903 by Paul Remlinger (1871–1964), director of the Imperial Bacteriology Institute of Constantinople [ 88 ]. At the beginning of the 20th century, in Italy, Claudio Fermi (1862–1952), a doctor who worked at the Institute of Hygiene in Rome, questioned the preparation of the vaccine. He applied the Toussaint’s method, exposure to phenol, developing a vaccine that was simpler, more effective, and above all safer, without risk of transmission since the virulence was essentially eliminated. The poor value of the vaccine as it had been defined by Pasteur from dehydrated spinal cord was demonstrated by one of his heirs within the institution he had created: Pierre Lépine (1901–1989), a physician who had joined Professor Constantin Levaditi (1874–1953) in 1927. Lépine was director of the Institut Pasteur in Athens from 1930 to 1935, then head of the virology department at the Institut Pasteur in Paris from 1940 to 1971. In 1937, Lépine undertook a comparative study of the rabies vaccines of Pasteur and Fermi. He demonstrated by injecting 40 rabbits that the protective power of the Pasteur vaccine was 35%, while tested on 52 rabbits, Fermi’s vaccine reached a protection rate of 77.7% [ 89 ].

8. Concluding Remarks

After Jenner, Béchamp, Toussaint, and Galtier, Pasteur allowed vaccination to acquire its credentials. However, it was not until the experiments of Emil von Behring (1854–1917), Shibasaburo Kitasato (1853–1931), and Paul Ehrlich (1854–1915) that science could fully understand the exact nature of the immune host response [ 90 , 91 ]. Pasteur, as a microbiologist, conceived of the protection acquired by vaccination by attenuated bacteria as a consumption of the nutritional requirements needed for the growth and survival of the microbe, just as a culture media contained only trace amounts of vital nutrients. Thus, the host would not support the growth of a subsequent infection by the same microbe [ 92 ]. Pasteur admitted that the use of dead germs for vaccines did not fit with his own explanation.

In his obituary published in Science in 1895, the American bacteriologist H.W. Conn, director of the Cold Spring Biological laboratory, wrote: “ Pasteur is regarded as the father of modern bacteriology, but we must remember that he was not a pioneer in these lines of work. There was hardly a problem that he studied which had not been already recognized, and even studied to a greater or less extent by his predecessors ”, but nicely adding “ Others discovered facts, Pasteur determined laws ” [ 93 ]. Fifty years later, when a special exhibition devoted to Louis Pasteur was organized in London (1947), Alexander Fleming paid tribute to the great scientist. He cited many of those who, with Pasteur, contributed to the fight against microbes, but he failed to mention Béchamp, Toussaint, Feltz, Duboué, or Galtier, illustrating that Pasteur’s efforts to minimize the role played by his precursors had been successful. The legend was written and even a leading figure would not dare to flout it [ 94 ].

Author Contributions

J.-M.C. and S.L. contributed to gather the historical information and to write of the manuscript. All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Institutional Review Board Statement

Informed consent statement, data availability statement, conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Louis Pasteur

Louis Pasteur was born on December 27, 1822 in Dole, a small town in eastern France. As a youngster he showed talent as an artist, but no special ability in school. This changed however, in his high school years, as he became more and more interested in scientific subjects. In 1842, he completed his Bachelor of Science degree at the Besancon College Royal de la Franche with honors in physics, mathematics, and Latin. He moved on to the Ecole Normale Superieure in Paris to study physics and chemistry.  He received his doctoral degree in 1847.

Eventually Pasteur would solve such scientific mysteries as the generation of ailments like rabies, anthrax and chicken cholera, and contributing to the world’s first and most significant vaccines.  He also described the process of fermentation for the first time, invented the process of pasteurization, and developed important scientific theories such as the germ theory of disease. He began his career working as a chemist, studying the shapes of organic crystals. He was able to prove that the organic molecules with the same chemical composition can exist in space in unique stereo specific forms. And with this work, at just 26 years of age, Pasteur launched the new science of stereochemistry.

Pasteur served on the faculty of science of Dijon briefly and then transferred to Strasbourg University where he met and married Marie Laurent. They would later have five children, three of whom died of typhoid fever.  This might have helped motivate Pasteur to save people from diseases later in his career. In 1854, Pasteur was appointed Dean and professor of chemistry at the Faculty of Sciences in Lille, France.

In 1856, the father of one of Pasteur’s chemistry students asked him to help him solve some problems he was encountering in his attempt to make alcohol by fermenting beetroot. Often, instead of alcohol, the fermentations yielded lactic acid. At the time, fermentation was believed to be a pure chemical process in which sugar was transformed into alcohol. But in 1857, Pasteur proved that a microscopic plant caused the souring of milk (lactic acid fermentation). Pasteur was able to prove that living cells, the yeast, were responsible for forming alcohol from sugar, and that contaminating microorganisms found in ordinary air could turn the fermentations sour. Next he identified the microorganisms responsible for both normal and abnormal fermentations, and found that through heating wine, beer, milk, or vinegar briefly, certain living organisms could be killed, thereby sterilizing – or “pasteurizing” – the substances.

This lead to Pasteur's thought that if germs were the cause of fermentation, they could also be the cause of contagious diseases. He began to develop his germ theory of disease, and eventually, to his work on vaccinations. In the 1870s, Pasteur had been attempting to solve the serious problem farmers were having with chicken cholera. The disease could spread through an entire farm in three days. While Pasteur and colleagues had been culturing the cholera microbes and injecting them into test chickens, they found that if they injected the birds with live microbes after they had already been injected with a weaker quantity of the organisms, that they would be unaffected.

This discovery lead Pasteur to wonder if it could also work for anthrax, a disease that was especially devastating to sheep and cattle. In 1881, Pasteur successfully demonstrated his anthrax vaccine to the public. Within ten years more than 3.5 million sheep and a half million cattle had been vaccinated with a mortality of less than one percent. This work lead to Pasteur’s identification of the germs causing many other diseases, such as swine erysipelas, childbirth fever and pneumonia. Pasteur is also credited for installing physicians’ adoption of the rules of antiseptic medicine and surgery.

In 1885, Pasteur was lauded for one of his most famous developments -- a vaccine against rabies (or “hydrophobia”). He had successfully vaccinated dogs against the disease; soon after the vaccine was tested successfully on humans. Subsequently, the Pasteur Institute was built in Paris to treat victims of rabies. Additional Pasteur Institutes were later built around the world to treat with rabies and other diseases.

Pasteur died in 1895 after suffering multiple strokes. He was buried, a national hero, by the French Government in the Cathedral of Notre Dame, and his remains were transferred to a permanent crypt in the Pasteur Institute, Paris.

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ARTS & CULTURE

When food changed history: louis pasteur.

If you’ve never considered the connection between beet juice and rabies prevention, read on

Lisa Bramen

If you've never considered the connection between beet juice and rabies prevention, read on.

This is the first installment in an occasional series about important food-related events in history. I can think of no better subject to begin with than the scientist whose discoveries led to important innovations in both food preservation and prevention of infectious disease, Louis Pasteur. And although he can't be credited with inventing the process that turns grapes into chianti and grain into amber bock, he was the first to explain the role of microorganisms in fermentation, and his work led to improvements in beer and wine making.

Pasteur was born in Dôle, France in 1822. He first gained acclaim as a young professor for his studies in how certain crystals affect light. He continued his work on crystallography at the University of Strasbourg, in the Alsace region of France, where he concluded that asymmetry was the defining characteristic of the molecules of living things, while the molecules of minerals were symmetrical—an important contribution to the scientific understanding of life. He also experimented with the effect of heat on molecular structures, and made his first foray into medical applications, developing a new and more stable isomer of quinine, which was used to treat fever.

But Pasteur's most famous discoveries were made after he became dean of the science department at the University of Lille, in a region known for its beet juice distilleries. In 1856, a local industrialist approached him about the quality problems some manufacturers of beet root alcohol were having. Pasteur set about studying yeast under a microscope.

Patrice Debré writes in his 1994 biography Pasteur , "Indeed we are indebted to fermentation for some of the most powerful symbols of our myths, at least in the Western tradition. The ancient Egyptians brewing beer, the ancient Gauls making their bread dough rise with yeast—these images evoke ancestral practices. Yet scientists, including the earliest chemists, from Paracelsus to Robert Boyle, had no convincing explanation to account for the phenomenon."

In Pasteur's time, Debré explains, yeast was thought to have only a passive role in fermentation. His experiments showed that yeast was not only the cause of fermentation, but that it was a living microorganism and that fermentation was the result of a biological rather than chemical process. His research became the basis for the new field of microbiology. It also paved the way for a number of other important advancements in science, including his debunking of the centuries-old and widely held idea of spontaneous generation —that some life forms, like rats and flies, could arise spontaneously from non-living matter under certain circumstances.

Pasteur's promotion of the germ theory —which proposed that many diseases, such as anthrax and rabies, are caused by microorganisms—led to a new understanding of how infectious disease spreads, and therefore how to prevent it. Sanitary practices in medicine followed. The capstone of his long and fruitful career, according to Debré, was his role in the development of a rabies vaccine. This led to the establishment of the Institut Pasteur , in 1887, which continues to research the prevention and treatment of infectious disease.

Of course, the achievement most obviously associated with Pasteur, and most relevant to this blog, is the process of pasteurization. In 1863 Pasteur received a letter from one of Napoleon III's aides, commissioning him to study the spoilage of wine—a matter of great urgency in France, where wine was vital to the nation's cultural life and economic prosperity. The aide wrote, "The Emperor is firmly convinced that it would be of the highest importance that you turn your attention in this direction at the time of the grape harvest." Drawing on his earlier research, Pasteur developed a method of heating wine to slow microbial growth and prevent spoilage, without destroying the beverage in the process. Pasteurization, as it came to be known, is still used to treat wine, milk and other perishable liquids.

So next time you enjoy a pinot noir, or chocolate milk, raise your glass to Louis Pasteur.

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Lisa Bramen | | READ MORE

Lisa Bramen was a frequent contributor to Smithsonian.com's Food and Think blog. She is based in northern New York and is also an associate editor at Adirondack Life magazine.

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Louis pasteur’s devotion to truth transformed what we know about health and disease.

Louis Pasteur demonstrated, more dramatically than any other scientist, the benefit of science for humankind.

Sam Falconer

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By Tom Siegfried

November 18, 2022 at 7:00 am

Great scientists become immortalized in various ways.

Some through names for obscure units of measurement (à la Hertz, Faraday and Curie). Others in elements on the periodic table ( Mendeleev , Seaborg, Bohr , among many others). A few become household names symbolizing genius — like Newton in centuries past and nowadays, Einstein . But only one has been honored on millions and millions of cartons of milk: the French chemist, biologist and evangelist for experimental science Louis Pasteur.

Pasteur was born 200 years ago this December, the most significant scientist birthday bicentennial since Charles Darwin’s in 2009 . And Pasteur ranked behind only Darwin among the most exceptional biological scientists of the 19th century.

Pasteur not only made milk safe to drink, but also rescued the beer and wine industry. He established the germ theory of disease, saved the French silkworm population, confronted the scourges of anthrax and rabies, and transformed the curiosity of vaccination against smallpox into a general strategy for treating and preventing human diseases. He invented microbiology and established the foundations for immunology.

Had he been alive after 1901, when Nobel Prizes were first awarded, he would have deserved one every year for a decade. No other single scientist demonstrated more dramatically the benefit of science for humankind.

He was not, however, exactly a saint. A Pasteur biographer, Hilaire Cuny, called him “a mass of contradictions.” Pasteur was ambitious and opportunistic, sometimes arrogant and narrow-minded, immodest, undiplomatic and uncompromising. In the scientific controversies he engaged in (and there were many), he was pugnacious and belligerent. He did not suffer criticism silently and was often acerbic in his responses. To his laboratory assistants, he was demanding, dictatorial and aloof. Despite his revolutionary spirit in pursuing science, in political and social matters, he was conformist and deferential to authority.

And yet he was a tireless worker, motivated by service to humankind, faithful to his family and unwaveringly honest. He was devoted to truth, and therefore also to science.

How Pasteur developed pasteurization

In his youth, Pasteur did not especially excel as a student. His interests inclined toward art rather than science, and he did display exceptional skill at drawing and painting. But in light of career considerations (his father wanted him to be a scholar), Pasteur abandoned art for science and so applied to the prestigious École Normale Supérieure in Paris for advanced education. He finished 15th in the competitive entrance examination, good enough to secure admission. But not good enough for Pasteur. He spent another year on further studies emphasizing physical sciences and then took the École Normale exam again, finishing fourth. That was good enough, and he entered the school in 1843. There he earned his doctoral degree, in physics and chemistry, in 1847.

Among his special interests at the École Normale was crystallography. In particular he was drawn to investigate tartaric acid. It’s a chemical found in grapes responsible for tartar, a potassium compound that collects on the surfaces of wine vats. Scientists had recently discovered that tartaric acid possesses the intriguing power of twisting light — that is, rotating the orientation of light waves’ vibrations. In light that has been polarized (by passing it through certain crystals, filters or some sunglasses), the waves are all aligned in a single plane. Light passing through a tartaric acid solution along one plane emerges in a different plane.

Even more mysteriously, another acid (paratartaric acid, or racemic acid), with the exact same chemical composition as tartaric acid, did not twist light at all. Pasteur found that suspicious. He began a laborious study of the crystals of salts derived from the two acids. He discovered that racemic acid crystals could be sorted into two asymmetric mirror-image shapes, like pairs of right-handed and left-handed gloves. All the tartaric acid crystals, on the other hand, had shapes with identical asymmetry, analogous to gloves that were all right-handed.

Pasteur deduced that the asymmetry in the crystals reflected the asymmetric arrangement of atoms in their constituent molecules. Tartaric acid twisted light because of the asymmetry of its molecules, while in racemic acid, the two opposite shapes canceled out each other’s twisting effects.

Pasteur built the rest of his career on this discovery. His research on tartaric acid and wine led eventually to profound realizations about the relationship between microbes and human disease. Before Pasteur, most experts asserted that fermentation was a natural nonbiological chemical process. Yeast, a necessary ingredient in the fermenting fluid, was supposedly a lifeless chemical acting as a catalyst. Pasteur’s experiments showed yeast to be alive, a peculiar kind of “small plant” (now known to be a fungus) that caused fermentation by biological activity.

Pasteur demonstrated that, in the absence of air, yeast acquired oxygen from sugar, converting the sugar to alcohol in the process. “Fermentation by yeast,” he wrote, is “the direct consequence of the processes of nutrition,” a property of a “minute cellular plant … performing its respiratory functions.” Or more succinctly, he proclaimed that “fermentation … is life without air.” (Later scientists found that yeast accomplished fermentation by emitting enzymes that catalyzed the reaction.)

Pasteur also noticed that additional microorganisms present during fermentation could be responsible for the process going awry, a problem threatening the viability of French winemaking and beer brewing. He solved that problem by developing a method of heating that eliminated the bad microorganisms while preserving the quality of the beverages. This method, called “pasteurization,” was later applied to milk, eliminating the threat of illness from drinking milk contaminated by virulent microorganisms. Pasteurization became standard public health practice in the 20th century.

Incorporating additional insights from studies of other forms of fermentation, Pasteur summarized his work on microbial life in a famous paper published in 1857. “This paper can truly be regarded as the beginning of scientific microbiology,” wrote the distinguished microbiologist René Dubos, who called it “one of the most important landmarks of biochemical and biological sciences.”

The germ theory of disease is born

Pasteur’s investigations of the growth of microorganisms in fermentation collided with another prominent scientific issue: the possibility of spontaneous generation of life. Popular opinion even among many scientists held that microbial life self-generated under the proper conditions (spoiled meat, for example). Demonstrations by the 17th century Italian scientist Francesco Redi challenged that belief , but the case against spontaneous generation was not airtight.

In the early 1860s Pasteur undertook a series of experiments that should have left no doubt that spontaneous generation, under conditions encountered on Earth today, was an illusion. Yet he was nevertheless accosted by critics, such as the French biologist Charles-Philippe Robin, to whom he returned verbal fire. “We trust that the day will come when M. Robin will … acknowledge that he has been in error on the subject of the doctrine of spontaneous generation, which he continues to affirm, without adducing any direct proofs in support of it,” Pasteur remarked.

It was his work on spontaneous generation that led Pasteur directly to the development of the germ theory of disease.

For centuries people had suspected that some diseases must be transmitted from person to person by close contact. But determining exactly how that happened seemed beyond the scope of scientific capabilities. Pasteur, having discerned the role of germs in fermentation, saw instantly that something similar to what made wine go bad might also harm human health.

After disproving spontaneous generation, he realized that there must exist “transmissible, contagious, infectious diseases of which the cause lies essentially and solely in the presence of microscopic organisms.” For some diseases, at least, it was necessary to abandon “the idea of … an infectious element suddenly originating in the bodies of men or animals.” Opinions to the contrary, he wrote, gave rise “to the gratuitous hypothesis of spontaneous generation” and were “fatal to medical progress.”

His first foray into applying the germ theory of disease came during the late 1860s in response to a decline in French silk production because of diseases afflicting silkworms. After success in tackling the silkworms’ maladies, he turned to anthrax, a terrible illness for cattle and humans alike. Many medical experts had long suspected that some form of bacteria caused anthrax, but it was Pasteur’s series of experiments that isolated the responsible microorganism, verifying the germ theory beyond doubt. (Similar work by Robert Koch in Germany around the same time provided further confirmation.)

Understanding anthrax’s cause led to the search for a way to prevent it. In this case, a fortuitous delay in Pasteur’s experiments with cholera in chickens produced a fortunate surprise. In the spring of 1879 he had planned to inject chickens with cholera bacteria he had cultured, but he didn’t get around to it until after his summer vacation. When he injected his chickens in the fall, they unexpectedly failed to get sick. So Pasteur prepared a fresh bacterial culture and brought in a new batch of chickens.

When both the new chickens and the previous batch were given the fresh bacteria, the new ones all died, while nearly all of the original chickens still remained healthy. And so, Pasteur realized, the original culture had weakened in potency over the summer and was unable to cause disease, while the new, obviously potent culture did not harm the chickens previously exposed to the weaker culture. “These animals have been vaccinated,” he declared.

Vaccination, of course, had been invented eight decades earlier, when British physician Edward Jenner protected people from smallpox by first exposing them to cowpox, a similar disease acquired from cows. (Vaccination comes from cowpox’s medical name, vaccinia, from vacca , Latin for cow.) Pasteur realized that the chickens surprisingly displayed a similar instance of vaccination because he was aware of Jenner’s discovery. “Chance favors the prepared mind,” Pasteur was famous for saying.

Because of his work on the germ theory of disease, Pasteur’s mind was prepared to grasp the key role of microbes in the prevention of smallpox, something Jenner could not have known. And Pasteur instantly saw that the specific idea of vaccination for smallpox could be generalized to other diseases. “Instead of depending on the chance finding of naturally occurring immunizing agents, as cowpox was for smallpox,” Dubos observed, “it should be possible to produce vaccines at will in the laboratory.”

Pasteur cultured the anthrax microbe and weakened it for tests in farm animals. Success in such tests not only affirmed the correctness of the germ theory of disease, but also allowed it to gain a foothold in devising new medical practices.

Later Pasteur confronted an even more difficult microscopic foe, the virus that causes rabies. He had begun intense experiments on rabies, a horrifying disease that’s almost always fatal, caused usually by the bites of rabid dogs or other animals. His experiments failed to find any bacterial cause for rabies, leading him to realize that it must be the result of some agent too small to see with his microscope. He could not grow cultures in lab dishes of what he could not see. So instead he decided to grow the disease-causing agent in living tissue — the spinal cords of rabbits. He used dried-out strips of spinal cord from infected rabbits to vaccinate other animals that then survived rabies injections.

Pasteur hesitated to test his rabies treatment on humans. Still, in 1885 when a mother brought to his lab a 9-year-old boy who had been badly bitten by a rabid dog, Pasteur agreed to administer the new vaccine. After a series of injections, the boy recovered fully. Soon more requests came for the rabies vaccine, and by early the next year over 300 rabies patients had received the vaccine and survived, with only one death among them.

Popularly hailed as a hero, Pasteur was also vilified by some hostile doctors, who considered him an uneducated interloper in medicine. Vaccine opponents complained that his vaccine was an untested method that might itself cause death. But of course, critics had also rejected Pasteur’s view of fermentation, the germ theory of disease and his disproof of spontaneous generation.

Pasteur stood his ground and eventually prevailed (although he did not turn out to be right about everything). His attitude and legacy of accomplishments inspired 20th century scientists to develop vaccines for more than a dozen deadly diseases. Still more diseases succumbed to antibiotics, following the discovery of penicillin by Alexander Fleming — who declared, “Without Pasteur I would have been nothing.”

Even in Pasteur’s own lifetime, thanks to his defeat of rabies, his public reputation was that of a genius.

Pasteur’s scientific legacy

As geniuses go, Pasteur was the opposite of Einstein. To get inspiration for his theories, Einstein imagined riding aside a light beam or daydreamed about falling off a ladder. Pasteur stuck to experiments. He typically initiated his experiments with a suspected result in mind, but he was scrupulous in verifying the conclusions he drew from them. Preconceived ideas, he said, can guide the experimenter’s interrogation of nature but must be abandoned in light of contrary evidence. “The greatest derangement of the mind,” he declared, “is to believe in something because one wishes it to be so.”

So even when Pasteur was sure his view was correct, he insisted on absolute proof, conducting many experiments over and over with variations designed to rule out all but the true interpretation.

“If Pasteur was a genius, it was not through ethereal subtlety of mind,” wrote Pasteur scholar Gerald Geison. Rather, he exhibited “clear-headedness, extraordinary experimental skill and tenacity — almost obstinacy — of purpose.”

His tenacity, or obstinacy, helped him persevere through several personal tragedies, such as the deaths of three of his daughters, in 1859, 1865 and 1866. And then in 1868 he suffered a cerebral hemorrhage that left him paralyzed on his left side. But that did not slow his pace or impair continuing his investigations.

“Whatever the circumstances in which he had to work, he never submitted to them, but instead molded them to the demands of his imagination and his will,” Dubos wrote. “He was probably the most dedicated servant that science ever had.”

To the end of his life, Pasteur remained dedicated to science and the scientific method, stressing the importance of experimental science for the benefit of society. Laboratories are “sacred institutions,” he asserted. “Demand that they be multiplied and adorned; they are the temples of wealth and of the future.”

Three years before his death in 1895, Pasteur further extolled the value of science and asserted his optimism that the scientific spirit would prevail. In an address, delivered for him by his son, at a ceremony at the Sorbonne in Paris, he expressed his “invincible belief … that science and peace will triumph over ignorance and war, that nations will unite, not to destroy, but to build, and that the future will belong to those who will have done most for suffering humanity.”

Two hundred years after his birth , ignorance and war remain perniciously prominent, as ineradicable as the microbes that continue to threaten public health, with the virus causing COVID-19 the latest conspicuous example. Vaccines, though, have substantially reduced the risks from COVID-19, extending the record of successful vaccines that have already tamed not only smallpox and rabies, but also polio, measles and a host of other once deadly maladies .

Yet even though vaccines have saved countless millions of lives, some politicians and so-called scientists who deny or ignore overwhelming evidence continue to condemn vaccines as more dangerous than the diseases they prevent. True, some vaccines can induce bad reactions, even fatal in a few cases out of millions of vaccinations. But shunning vaccines today, as advocated in artificially amplified social media outrage, is like refusing to eat because some people choke to death on sandwiches.

Today, Pasteur would be vilified just as he was in his own time, probably by some people who don’t even realize that they can safely drink milk because of him. Nobody knows exactly what Pasteur would say to these people now. But it’s certain that he would stand up for truth and science, and would be damn sure to tell everybody to get vaccinated.

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Yeast Fermentation and the Making of Beer and Wine

Once upon a time, many, many years ago, a man found a closed fruit jar containing a honeybee. When he drank the contents, he tasted a new, strange flavor. Suddenly his head was spinning, he laughed for no reason, and he felt powerful. He drank all the liquid in the jar. The next day he experienced an awful feeling. He had a headache, pain , an unpleasant taste in his mouth, and dizziness — he had just discovered the hangover. You might think this is just a tale, but is it? Several archaeological excavations have discovered jars containing the remains of wine that are 7,000 years old (McGovern, 2009), and it is very likely that humankind's first encounter with alcoholic beverages was by chance. How did this chance discovery lead to the development of the beer and wine industry (Figure 1), and how did scientists eventually learn about the biological mechanisms of alcohol production?

The History of Beer and Wine Production

Over the course of human history, and using a system of trial, error, and careful observation, different cultures began producing fermented beverages. Mead, or honey wine, was produced in Asia during the Vedic period (around 1700–1100 BC), and the Greeks, Celts, Saxons, and Vikings also produced this beverage. In Egypt, Babylon, Rome, and China, people produced wine from grapes and beer from malted barley. In South America, people produced chicha from grains or fruits, mainly maize; while in North America, people made octli (now known as "pulque") from agave, a type of cactus (Godoy et al. 2003).

At the time, people knew that leaving fruits and grains in covered containers for a long time produced wine and beer, but no one fully understood why the recipe worked. The process was named fermentation, from the Latin word fervere , which means "to boil." The name came from the observation that mixtures of crushed grapes kept in large vessels produced bubbles, as though they were boiling. Producing fermented beverages was tricky. If the mixture did not stand long enough, the product contained no alcohol; but if left for too long, the mixture rotted and was undrinkable. Through empirical observation, people learned that temperature and air exposure are key to the fermentation process.

Wine producers traditionally used their feet to soften and grind the grapes before leaving the mixture to stand in buckets. In so doing, they transferred microorganisms from their feet into the mixture. At the time, no one knew that the alcohol produced during fermentation was produced because of one of these microorganisms — a tiny, one-celled eukaryotic fungus that is invisible to the naked eye: yeast . It took several hundred years before quality lenses and microscopes revolutionized science and allowed researchers to observe these microorganisms.

Yeast and Fermentation

Figure 1: Fermented beverages such as wine have been produced by different human cultures for centuries. Christian Draghici/Shutterstock. All rights reserved. In the seventeenth century, a Dutch tradesman named Antoni van Leeuwenhoek developed high-quality lenses and was able to observe yeast for the first time. In his spare time Leeuwenhoek used his lenses to observe and record detailed drawings of everything he could, including very tiny objects, like protozoa, bacteria , and yeast. Leeuwenhoek discovered that yeast consist of globules floating in a fluid, but he thought they were merely the starchy particles of the grain from which the wort (liquid obtained from the brewing of whiskey and beer) was made (Huxley 1894). Later, in 1755, yeast were defined in the Dictionary of the English Language by Samuel Johnson as "the ferment put into drink to make it work; and into bread to lighten and swell it." At the time, nobody believed that yeast were alive; they were seen as just organic chemical agents required for fermentation.

In the eighteenth and nineteenth centuries, chemists worked hard to decipher the nature of alcoholic fermentation through analytical chemistry and chemical nomenclature. In 1789, the French chemist Antoine Lavoisier was working on basic theoretical questions about the transformations of substances. In his quest, he decided to use sugars for his experiments, and he gained new knowledge about their structures and chemical reactions. Using quantitative studies, he learned that sugars are composed of a mixture of hydrogen, charcoal (carbon), and oxygen.

Lavoisier was also interested in analyzing the mechanism by which sugarcane is transformed into alcohol and carbon dioxide during fermentation. He estimated the proportions of sugars and water at the beginning of the chemical reaction and compared them with the alcohol and carbon dioxide proportions obtained at the end. For the alcoholic reaction to proceed, he also added yeast paste (or "ferment," as it was called). He concluded that sugars were broken down through two chemical pathways: Two-thirds of the sugars were reduced to form alcohol, and the other third were oxidized to form carbon dioxide (the source of the bubbles observed during fermentation). Lavoisier predicted (according to his famous conservation-of-mass principle) that if it was possible to combine alcohol and carbon dioxide in the right proportions, the resulting product would be sugar. The experiment provided a clear insight into the basic chemical reactions needed to produce alcohol. However, there was one problem: Where did the yeast fit into the reaction? The chemists hypothesized that the yeast initiated alcoholic fermentation but did not take part in the reaction. They assumed that the yeast remained unchanged throughout the chemical reactions.

Yeast Are Microorganisms

In 1815 the French chemist Joseph-Louis Gay-Lussac made some interesting observations about yeast. Gay-Lussac was experimenting with a method developed by Nicolas Appert, a confectioner and cooker, for preventing perishable food from rotting. Gay-Lussac was interested in using the method to maintain grape juice wort in an unfermented state for an indefinite time. The method consisted of boiling the wort in a vessel, and then tightly closing the vessel containing the boiling fluid to avoid exposure to air. With this method, the grape juice remained unfermented for long periods as long as the vessel was kept closed. However, if yeast (ferment) was introduced into the wort after the liquid cooled, the wort would begin to ferment. There was now no doubt that yeast were indispensable for alcoholic fermentation. But what role did they play in the process?

When more powerful microscopes were developed, the nature of yeast came to be better understood. In 1835, Charles Cagniard de la Tour, a French inventor, observed that during alcoholic fermentation yeast multiply by gemmation (budding). His observation confirmed that yeast are one-celled organisms and suggested that they were closely related to the fermentation process. Around the same time, Theodor Schwann, Friedrich Kützing, and Christian Erxleben independently concluded that "the globular, or oval, corpuscles which float so thickly in the yeast [ferment] as to make it muddy" were living organisms (Barnett 1998). The recognition that yeast are living entities and not merely organic residues changed the prevailing idea that fermentation was only a chemical process. This discovery paved the way to understand the role of yeast in fermentation.

Pasteur Demonstrates the Role of Yeast in Fermentation

Pasteur performed careful experiments and demonstrated that the end products of alcoholic fermentation are more numerous and complex than those initially reported by Lavoisier. Along with alcohol and carbon dioxide, there were also significant amounts of glycerin, succinic acid, and amylic alcohol (some of these molecules were optical isomers — a characteristic of many important molecules required for life). These observations suggested that fermentation was an organic process. To confirm his hypothesis, Pasteur reproduced fermentation under experimental conditions, and his results showed that fermentation and yeast multiplication occur in parallel. He realized that fermentation is a consequence of the yeast multiplication, and the yeast have to be alive for alcohol to be produced. Pasteur published his seminal results in a preliminary paper in 1857 and in a final version in 1860, which was titled "Mémoire sur la fermentation alcoolique" (Pasteur 1857).

In 1856, a man named Bigo sought Pasteur's help because he was having problems at his distillery, which produced alcohol from sugar beetroot fermentation. The contents of his fermentation containers were embittered, and instead of alcohol he was obtaining a substance similar to sour milk. Pasteur analyzed the chemical contents of the sour substance and found that it contained a substantial amount of lactic acid instead of alcohol. When he compared the sediments from different containers under the microscope, he noticed that large amounts of yeast were visible in samples from the containers in which alcoholic fermentation had occurred. In contrast, in the polluted containers, the ones containing lactic acid, he observed "much smaller cells than the yeast." Pasteur's finding showed that there are two types of fermentation: alcoholic and lactic acid. Alcoholic fermentation occurs by the action of yeast; lactic acid fermentation, by the action of bacteria.

Isolating the Cell's Chemical Machinery

By the end of the nineteenth century, Eduard Buchner had shown that fermentation could occur in yeast extracts free of cells, making it possible to study fermentation biochemistry in vitro . He prepared cell-free extracts by carefully grinding yeast cells with a pestle and mortar. The resulting moist mixture was put through a press to obtain a "juice" to which sugar was added. Using a microscope, Buchner confirmed that there were no living yeast cells in the extract.

Upon studying the cell-free extracts, Buchner detected zymase, the active constituent of the extracts that carries out fermentation. He realized that the chemical reactions responsible for fermentation were occurring inside the yeast. Today researchers know that zymase is a collection of enzymes (proteins that promote chemical reactions). Enzymes are part of the cellular machinery, and all of the chemical reactions that occur inside cells are catalyzed and modulated by enzymes. For his discoveries, Buchner was awarded the Nobel Prize in Chemistry in 1907 (Barnett 2000; Barnett & Lichtenthaler 2001; Encyclopaedia Britannica 2010).

Around 1929, Karl Lohmann, Yellapragada Subbarao, and Cirus Friske independently discovered an essential molecule called adenosine triphosphate ( ATP ) in animal tissues. ATP is a versatile molecule used by enzymes and other proteins in many cellular processes. It is required for many chemical reactions, such as sugar degradation and fermentation (Voet & Voet 2004). In 1941, Fritz Albert Lipmann proposed that ATP was the main energy transfer molecule in the cell.

Sugar Decomposition

Glycolysis — the metabolic pathway that converts glucose (a type of sugar) into pyruvate — is the first major step of fermentation or respiration in cells. It is an ancient metabolic pathway that probably developed about 3.5 billion years ago, when no oxygen was available in the environment . Glycolysis occurs not only in microorganisms, but in every living cell (Nelson & Cox 2008).

Because of its importance, glycolysis was the first metabolic pathway resolved by biochemists. The scientists studying glycolysis faced an enormous challenge as they figured out how many chemical reactions were involved, and the order in which these reactions took place. In glycolysis, a single molecule of glucose (with six carbon atoms) is transformed into two molecules of pyruvic acid (each with three carbon atoms).

In order to understand glycolysis, scientists began by analyzing and purifying the labile component of cell-free extracts, which Buchner called zymase. They also detected a low-molecular-weight, heat-stable molecule, later called cozymase. Using chemical analyses, they learned that zymase is a complex of several enzymes; and cozymase is a mixture of ATP, ADP (adenosine diphosphate, a hydrolyzed form of ATP), metals, and coenzymes (substances that combine with proteins to make them functional), such as NAD + (nicotinamide adenine dinucleotide). Both components were required for fermentation to occur.

The complete glycolytic pathway, which involves a sequence of ten chemical reactions, was elucidated around 1940. In glycolysis, two molecules of ATP are produced for each broken molecule of glucose. During glycolysis, two reduction-oxidation (redox) reactions occur. In a redox reaction, one molecule is oxidized by losing electrons, while the other molecule is reduced by gaining those electrons. A molecule called NADH acts as the electron carrier in glycolysis, and this molecule must be reconstituted to ensure continuity of the glycolysis pathway.

The Chemical Process of Fermentation

In the absence of oxygen (anoxygenic conditions), pyruvic acid can follow two different routes, depending on the type of cell . It can be converted into ethanol (alcohol) and carbon dioxide through the alcoholic fermentation pathway, or it can be converted into lactate through the lactic acid fermentation pathway (Figure 3).

Since Pasteur's work, several types of microorganisms (including yeast and some bacteria) have been used to break down pyruvic acid to produce ethanol in beer brewing and wine making. The other by-product of fermentation, carbon dioxide, is used in bread making and the production of carbonated beverages. Other living organisms (such as humans) metabolize pyruvic acid into lactate because they lack the enzymes needed for alcohol production, and in mammals lactate is recycled into glucose by the liver (Voet & Voet 2004).

Selecting Yeast in Beer Brewing and Wine Making

Humankind has benefited from fermentation products, but from the yeast's point of view, alcohol and carbon dioxide are just waste products. As yeast continues to grow and metabolize sugar, the accumulation of alcohol becomes toxic and eventually kills the cells (Gray 1941). Most yeast strains can tolerate an alcohol concentration of 10–15% before being killed. This is why the percentage of alcohol in wines and beers is typically in this concentration range. However, like humans, different strains of yeast can tolerate different amounts of alcohol. Therefore, brewers and wine makers can select different strains of yeast to produce different alcohol contents in their fermented beverages, which range from 5 percent to 21 percent of alcohol by volume. For beverages with higher concentrations of alcohol (like liquors), the fermented products must be distilled.

Today, beer brewing and wine making are huge, enormously profitable agricultural industries. These industries developed from ancient and empirical knowledge from many different cultures around the world. Today this ancient knowledge has been combined with basic scientific knowledge and applied toward modern production processes. These industries are the result of the laborious work of hundreds of scientists who were curious about how things work.

References and Recommended Reading

Barnett, J. A. A history of research on yeast 1: Work by chemists and biologists, 1789–1850. Yeast 14 , 1439–1451 (1998)

Barnett, J. A. A history of research on yeast 2: Louis Pasteur and his contemporaries, 1850–1880. Yeast 16 , 755–771 (2000)

Barnett, J. A. & Lichtenthaler, F. W. A history of research on yeast 3: Emil Fischer, Eduard Buchner and their contemporaries, 1880–1900. Yeast 18 , 363–388 (2001)

Encyclopaedia Britannica's Guide to the Nobel Prizes (2010)

Godoy, A., Herrera, T. & Ulloa, M. Más allá del pulque y el tepache: Las bebidas alcohólicas no destiladas indígenas de México. Mexico: UNAM, Instituto de Investigaciones Antropológicas, 2003

Gray, W. D. Studies on the alcohol tolerance of yeasts . Journal of Bacteriology 42 , 561–574 (1941)

Huxley, T. H. Popular Lectures and Addresses II . Chapter IV, Yeast (1871). Macmillan, 1894

Jacobs, J. Ethanol from sugar: What are the prospects for US sugar crops? Rural Cooperatives 73 (5) (2006)

McGovern, P. E. Uncorking the Past: The Quest for Wine, Beer, and Other Alcoholic Beverages. Berkeley: University of California Press, 2009

Nelson, D. L. & Cox, M. M. Lehninger Principles of Biochemistry , 5th ed. New York: Freeman, 2008

Pasteur, L. Mémoire sur la fermentation alcoolique .Comptes Rendus Séances de l'Academie des Sciences 45 , 913–916, 1032–1036 (1857)

Pasteur, L. Studies on Fermentation . London: Macmillan, 1876

Voet, D. & Voet, J. Biochemistry. Vol. 1, Biomolecules, Mechanisms of Enzyme Action, and Metabolism , 3rd ed. New York: Wiley, 2004

Classic papers:

Meyerhof, O. & Junowicz-Kocholaty, R. The equilibria of isomerase and aldolase, and the problem of the phosphorylation of glyceraldehyde phosphate . Journal of Biological Chemistry 149 , 71–92 (1943)

Meyerhof, O. The origin of the reaction of harden and young in cell-free alcoholic fermentation . Journal of Biological Chemistry 157 , 105–120 (1945)

Meyerhof, O. & Oesper, P. The mechanism of the oxidative reaction in fermentation . Journal of Biological Chemistry 170 , 1–22 (1947)

Pasteur, L. Mèmoire sur la fermentation appeleé lactique . Annales de Chimie et de Physique 3e. sér. 52 , 404–418 (1858)

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Louis Pasteur’s scientific discoveries in the 19th century revolutionized medicine and continue to save the lives of millions today

Regents' Professor of Clinical Laboratory Science, Texas State University

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Some of the greatest scientific discoveries haven’t resulted in Nobel Prizes.

Louis Pasteur , who lived from 1822 to 1895, is arguably the world’s best-known microbiologist. He is widely credited for the germ theory of disease and for inventing the process of pasteurization – which is named after him – to preserve foods. Remarkably, he also developed the rabies and anthrax vaccines and made major contributions to combating cholera .

But because he died in 1895, six years before the first Nobel Prize was awarded, that prize isn’t on his resume. Had he lived in the era of Nobel Prizes, he would undoubtedly have been deserving of one for his work. Nobel Prizes, which are awarded in various fields, including physiology and medicine , are not given posthumously.

During the current time of ongoing threats from emerging or reemerging infectious diseases, from COVID-19 and polio to monkeypox and rabies , it is awe-inspiring to look back on Pasteur’s legacy. His efforts fundamentally changed how people view infectious diseases and how to fight them via vaccines.

I’ve worked in public health and medical laboratories specializing in viruses and other microbes, while training future medical laboratory scientists . My career started in virology with a front-row seat to rabies detection and surveillance and zoonotic agents, and it rests in large part on Pasteur’s pioneering work in microbiology, immunology and vaccinology.

First, a chemist

In my assessment, Pasteur’s strongest contributions to science are his remarkable achievements in the field of medical microbiology and immunology. However, his story begins with chemistry.

Pasteur studied under the French chemist Jean-Baptiste-André Dumas . During that time, Pasteur became interested in the origins of life and worked in the field of polarized light and crystallography .

In 1848, just months after receiving his doctorate degree, Pasteur was studying the properties of crystals formed in the process of wine-making when he discovered that crystals occur in mirror-image forms , a property known as chirality. This discovery became the foundation of a subdiscipline of chemistry known as stereochemistry , which is the study of the spatial arrangement of atoms within molecules. This chirality, or handedness, of molecules was a “ revolutionary hypothesis ” at the time.

These findings led Pasteur to suspect what would later be proved through molecular biology: All life processes ultimately stem from the precise arrangement of atoms within biological molecules.

Wine and beer – from fermentation to germ theory

Beer and wine were critical to the economy of France and Italy in the 1800s. It was not uncommon during Pasteur’s life for products to spoil and become bitter or dangerous to drink. At the time, the scientific notion of “spontaneous generation” held that life can arise from nonliving matter, which was believed to be the culprit behind wine spoiling.

While many scientists tried to disprove the theory of spontaneous generation, in 1745, English biologist John Turberville Needham believed he had created the perfect experiment favoring spontaneous generation. Most scientists believed that heat killed life, so Needham created an experiment to show that microorganisms could grow on food, even after boiling. After boiling chicken broth, he placed it in a flask, heated it, then sealed it and waited, not realizing that air could make its way back into the flask prior to sealing. After some time, microorganisms grew, and Needham claimed victory.

However, his experiment had two major flaws . For one, the boiling time was not sufficient to kill all microbes. And importantly, his flasks allowed air to flow back in, which enabled microbial contamination.

To settle the scientific battle, the French Academy of Sciences sponsored a contest for the best experiment to prove or disprove spontaneous generation . Pasteur’s response to the contest was a series of experiments, including a prize-winning 1861 essay .

Pasteur deemed one of these experiments as “unassailable and decisive” because, unlike Needham, after he sterilized his cultures, he kept them free from contamination. By using his now famous swan-necked flasks, which had a long S-shaped neck, he allowed air to flow in while at the same time preventing falling particles from reaching the broth during heating. As a result, the flask remained free of growth for an extended period. This showed that if air was not allowed directly into his boiled infusions, then no “living microorganisms would appear, even after months of observation.” However, importantly, if dust was introduced, living microbes appeared.

Through that process, Pasteur not only refuted the theory of spontaneous generation, but he also demonstrated that microorganisms were everywhere. When he showed that food and wine spoiled because of contamination from invisible bacteria rather than from spontaneous generation, the modern germ theory of disease was born .

The origins of vaccination in the 1800s

In the 1860s, when the silk industry was being devastated by two diseases that were infecting silkworms , Pasteur developed a clever process by which to examine silkworm eggs under a microscope and preserve those that were healthy. Much like his efforts with wine, he was able to apply his observations into industry methods, and he became something of a French hero .

Even with failing health from a severe stroke that left him partially paralyzed, Pasteur continued his work. In 1878, he succeeded in identifying and culturing the bacterium that caused the avian disease fowl cholera . He recognized that old bacterial cultures were no longer harmful and that chickens vaccinated with old cultures could survive exposure to wild strains of the bacteria. And his observation that surviving chickens excreted harmful bacteria helped establish an important concept now all too familiar in the age of COVID-19 – asymptomatic “healthy carriers” can still spread germs during outbreaks.

After bird cholera, Pasteur turned to the prevention of anthrax , a widespread plague of cattle and other animals caused by the bacterium Bacillus anthracis . Building on his own work and that of German physician Robert Koch , Pasteur developed the concept of the attenuated, or weakened, versions of microbes for use in vaccines.

In the late 1880s, he showed beyond any doubt that exposing cattle to a weakened form of anthrax vaccine could lead to what is now well known as immunity, dramatically reducing cattle mortality.

The rabies vaccine breakthrough

In my professional assessment of Louis Pasteur, the discovery of vaccination against rabies is the most important of all his achievements.

Rabies has been called the “ world’s most diabolical virus ,” spreading from animal to human via a bite .

Working with rabies virus is incredibly dangerous, as mortality approaches 100% once symptoms appear and without vaccination. Through astute observation, Pasteur discovered that drying out the spinal cords of dead rabid rabbits and monkeys resulted in a weakened form of rabies virus. Using that weakened version as a vaccine to gradually expose dogs to the rabies virus, Pasteur showed that he could effectively immunize the dogs against rabies.

Then, in July 1885, Joseph Meister, a 9-year-old boy from France, was severely bitten by a rabid dog. With Joseph facing almost certain death, his mother took him to Paris to see Pasteur because she had heard that he was working to develop a cure for rabies.

Pasteur took on the case, and alongside two physicians, he gave the boy a series of injections over several weeks. Joseph survived and Pasteur shocked the world with a cure for a universally lethal disease. This discovery opened the door to the widespread use of Pasteur’s rabies vaccine around 1885, which dramatically reduced rabies’ deaths in humans and animals .

A Nobel Prize-worthy life

Pasteur once famously said in a lecture , “In the fields of observation, chance favors only the prepared mind.”

Pasteur had a knack for applying his brilliant – and prepared – scientific mind to the most practical dilemmas faced by humankind.

While Louis Pasteur died prior to the initiation of the Nobel Prize, I would argue that his amazing lifetime of discovery and contribution to science in medicine, infectious diseases, vaccination, medical microbiology and immunology place him among the all-time greatest scientists.

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Among Louis Pasteur’s discoveries were molecular asymmetry, the fact that molecules can have the same chemical composition with different structures; that fermentation is caused by microorganisms; and that virulence can be increased as well as decreased. He also disproved the theory of spontaneous generation and contributed to germ theory and the study of infectious disease.

Louis Pasteur is best known for inventing the process that bears his name, pasteurization . Pasteurization kills microbes and prevents spoilage in beer, milk, and other goods. In his work with silkworms, Pasteur developed practices that are still used today for preventing disease in silkworm eggs. Using his germ theory of disease, he also developed vaccines for chicken cholera, anthrax, and rabies.

What is pasteurization?

Pasteurization is a heat-treatment process that destroys pathogenic microorganisms in certain foods and beverages. It is used for preserving goods such as beer, milk, and cream.

Louis Pasteur grew up in a relatively poor family. He was one of four children, and his father was a tanner. In 1849 he married Marie Laurent, the daughter of the rector of the University of Strasbourg , where Pasteur was a professor of chemistry. They had five children together, only two of whom survived to adulthood.

Louis Pasteur (born December 27, 1822, Dole , France—died September 28, 1895, Saint-Cloud) was a French chemist and microbiologist who was one of the most important founders of medical microbiology . Pasteur’s contributions to science , technology , and medicine are nearly without precedent. He pioneered the study of molecular asymmetry; discovered that microorganisms cause fermentation and disease; originated the process of pasteurization ; saved the beer , wine , and silk industries in France ; and developed vaccines against anthrax and rabies .

Pasteur’s academic positions were numerous, and his scientific accomplishments earned him France’s highest decoration, the Legion of Honour , as well as election to the Académie des Sciences and many other distinctions. Today there are some 30 institutes and an impressive number of hospitals, schools, buildings, and streets that bear his name—a set of honours bestowed on few scientists.

Pasteur’s father, Jean-Joseph Pasteur, was a tanner and a sergeant major decorated with the Legion of Honour during the Napoleonic Wars . This fact probably instilled in the younger Pasteur the strong patriotism that later was a defining element of his character. Louis Pasteur was an average student in his early years, but he was gifted in drawing and painting. His pastels and portraits of his parents and friends, made when he was 15, were later kept in the museum of the Pasteur Institute in Paris . After attending primary school in Arbois, where his family had moved, and secondary school in nearby Besançon, he earned his bachelor of arts degree (1840) and bachelor of science degree (1842) at the Royal College of Besançon.

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Louis Pasteur: Biography, Inventions, Experiments & Facts

Louis Pasteur , the 19th-century French chemist and biologist, is known primarily as the "the father of germ theory," as he was the first scientist to offer formal support for the idea that microbes, or microscopic life forms, were responsible for the pathogenesis (the cause and progression) and transmission of certain diseases in humans, livestock and other animals.

As a consequence, his work in the realm of vaccines and food safety has led many science historians to observe that Pasteur's work has arguably saved more human lives than anyone else in the annals of history.

Pasteur, however, was the architect of a number of other groundbreaking ideas in the world of natural sciences, some of them unrelated or only tangentially related to his work in the area of infectious diseases.

In addition to introducing the concept of molecular asymmetry, Pasteur is credited with virtually saving both the wine and silk industries in his native France.

His ideas about how germs trigger the body to fight back against invaders have led to his being credited as "the father of immunology," making him, in effect, the "parent" of a pair of related yet distinct ideas in microbiology .

Louis Pasteur Biography

Born in Dole, France in 1822, Pasteur, like a lot of renowned figures in the comparative dawn of modern scientific exploration, did not limit himself to a single discipline.

The son of a sergeant major from whom he gained a strong sense of patriotism, Pasteur was reputedly only an average student as a child, though skilled in drawing and painting; some of his works are now displayed in the Pasteur Institute (Institut Pasteur).

The lad's creativity did not hearken to his brilliant future in science, which ultimately led him to receive the Legion of Honour, France's highest decoration.

After attending primary school in Arbois and secondary school (high school) as well as university in Besancon, Pasteur headed to the École Normale Supérieure in Paris – where he would later become director of scientific studies – in 1843, launching his science career in earnest.

Pasteur earned degrees in chemistry , physics and math, and, drawn initially to the first of these, became a professor of chemistry at the University of Strasbourg in 1848.

Three of his five children with his wife, Marie Laurent, whom Pasteur married in 1849, died from illness; many people believe that this was the main factor that prompted him to research diseases and illnesses, the real causes of virtually all of which were unknown at the time.

Molecular Asymmetry: Enantiomers

Perhaps like a future Academy Award-winning actor whose initial film role is obscure yet impressive, Pasteur's first major contribution to the body of scientific knowledge is not something he is widely remembered for. Pasteur produced the concept of molecular asymmetry , or the concept that molecules with the same chemical composition and bonding arrangement were not all actually the same shape.

Via meticulous experiments on the light-scattering properties of the tartaric acid found in wine (a hint of his work to follow), Pasteur's discovery demonstrated that chemically "identical" molecules can actually exist in mirror image – "left-handed" and "right-handed" – forms.

Further, he noted that all molecules in living things were left-handed. This was vitally important for understanding three-dimensional structures, especially in the science of crystallography .

Germs and Spontaneous Generation

Before Pasteur came along, most people believed in the notion of spontaneous generation , the idea that bacteria, microbes, germs and life in general appeared essentially out of nowhere, or from things like dust, dead flesh and even maggots.

The same theory was thus applied to illnesses: Weakness in an individual and the associated internal physical changes was presumed to allow these germs to appear, causing illnesses in an accordingly spontaneous way.

Pasteur, on the other hand, believed that these illnesses must arise from micro-organisms that themselves came from living things. That is, he theorized that "germs" didn't just appear out from scratch; they were living things in their own right. He achieved this through a series of elegant experiments that proved that food spoilage was a result of unseen elements in the air.

People were skeptical because Pasteur was not even a physician, but his work led to the development of antiseptics and revolutionized medicine.

Pasteur's Experiment: Fermentation

In his now-famous work involving fermentation , which is the oxygen-independent conversion of sugar by-products to alcohol and lactic acid, Pasteur showed that yeast is a living thing and an active part of the fermentation process . This was important in that it established fermentation as a biological process and not simply a chemical one.

Pasteur demonstrated that when air was pumped through the fermenting fluid, fermentation stopped. This showed that some kind of living organism that requires an oxygen-free environment has to be a part of the process. He was able to show that different microbes are responsible for different types of fermentation.

The Germ Theory of Disease

Pasteur was not the first to propose that unseen things in the environment could cause disease, but he was the first to offer evidence for the claim.

In experiments with beef broth, Pasteur showed that food would only spoil when exposed to microbes that were already present in the air. He applied these and similar findings to generate an elaborate germ theory of disease , which stated that bacteria and microbes cause disease, and that both diseases and their tiny causes exist in the world just like humans and other animals, rather than arising de novo ("from nothing").

This was no mere academic matter. By isolating a specific physical cause for diseases, Pasteur offered hope that these diseases could be prevented, thereby possibly staving off deaths like those that three of his children and countless others across Europe – for example, in the "Black Death" or bubonic plague of the 14th century, caused by the Yersinia pestis bacteria – had suffered.

Pasteur's Invention: Of Wine and Worms

Having come to understand that food and other things go bad not for mysterious or unpredictable reasons but because of bacteria, Pasteur was ready to address his home country's wine problem.

France had long been economically reliant on wine . Much of it was spoiling in transit because of bacterial contamination, but boiling the wine to kill the bacteria ruined the product. Using his signature methodical approach, Pasteur found that raising the wine to a certain intermediate temperature (55 C, or about 131 F) killed the bacteria without ruining the wine.

This process, now fittingly called pasteurization , has become universal in the food industry.

Pasteur's work with silkworms: Having rescued the wine industry, Pasteur used his knowledge of germ theory and disease to identify a parasite that was causing silkworm diseases. With the help of his wife, he was able to isolate the infected worms to get rid of the disease, thereby saving yet another vital sector of his country's economy.

Pasteur and Vaccines

In 1880, pushing the age of 60 but still as active as ever, Pasteur – who is sometimes erroneously credited with creating the first vaccine – developed the idea of vaccines with chickens. (Edward Jenner had developed a smallpox vaccine at the end of the 1700s, but with zero understanding of the underlying immunological mechanism.)

Pasteur showed that chickens, when inoculated (injected) with a non-virulent (non-disease-causing) form of the bacterial illness called chicken cholera, developed resistance to the virulent (disease-causing) types of cholera.

Pasteur's vaccine and others like it today, because they use living forms of the relevant organism, are called live attenuated vaccines, with "attenuated" meaning "thinned out."

Pasteur went on to use the same principles to produce an anthrax vaccine as well as a rabies vaccine, the latter demonstrating that the creation of vaccines for diseases caused by viruses rather than bacteria was possible, and also protecting against the bite of a rabid dog or other rabid animal.

On the basis of his contributions to both germ theory and immunology, Pasteur may be regarded as the father of microbiology and of preventive medicine in general.

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Louis Pasteur

AMERICAN PHILOSOPHICAL SOCIETY / SCIENCE PHOTO LIBRARY

Louis Pasteur was one of the first scientists to discover the role of microorganisms in disease and how sickness could be prevented by vaccines .

At the time, it was widely believed that putrefaction – the spoiling of food – and fermentation were chemical processes, caused by oxygen in the air. In the 1830s, two scientists, Theodor Schwann and Charles Cagniard de la Tour, used microscopes to observe that beer yeast was composed of reproducing cells, and proposed that alcohol was a product of their growth. Their ideas were largely ignored until Louis Pasteur carried out his own detailed experiments that disproved the chemical decomposition theory.

Another popular theory of the time was spontaneous generation – the idea, dating back to Aristotle, that living things could arise from inanimate material. Pasteur showed that if air was excluded from a boiled infusion, no living organisms appeared in it, but if atmospheric dust was allowed in, microbes would appear within days.

Pasteur realised that microbes were responsible for spoiling food, and just as importantly for France’s economy, wine. He discovered that heating wine to 55C killed bacteria and stopped wine from spoiling, without affecting the taste. The process became known as pasteurisation , and is still widely used today.

In 1880, Pasteur reported experiments on chicken cholera, which Jean Joseph Henri Toussaint had earlier isolated. Pasteur found that using certain culture techniques, it was possible to diminish the microbe’s virulence, and that inoculating chickens with these weakened microbes could immunise them against the disease. He believed that this principle could be applied to make vaccines against all infectious diseases.

Pasteur had no knowledge of the immune system. He thought that vaccines worked by depleting in the host essential nutrients needed by the pathogen, rendering the host unsuitable for later infection.

He went on to show that a vaccine could prevent sheep from becoming sick with anthrax in a celebrated trial. However, Pasteur used a vaccine prepared according to Toussaint’s method, not his own, and lied about it. The medical world did not know about his deception until his secret notebooks were made available to historians in the 1970s.

In 1885, a boy who had been bitten by a rabid dog turned up at Pasteur’s door. Pasteur gave him a series of injections, and he survived. His report claimed that he had made 50 dogs immune to rabies before treating the boy, but his notebooks revealed that he had only tested a few dogs.

Pasteur began manufacturing vaccines for anthrax and rabies commercially, and used the income to establish the Pasteur Institute.  Sam Wong

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Microbe Notes

Louis Pasteur and his contributions

• Louis Pasteur was a French chemist and microbiologist considered the most important founders of Microbiology.
• Microbiology developed as a scientific discipline from the era of Louis Pasteur (1822- 1895) himself.
• He first coined the term “microbiology” for the study of organisms of microscopic size. For his innumerable contributions in the field, he is also known as the Father of Microbiology .
• He is renowned for his discoveries of the principles of  vaccination , microbial fermentation and pasteurization.
• He is remembered for his remarkable breakthroughs in the causes and prevention of diseases.
• He is regarded as one of the three main founders of bacteriology, together with Ferdinand Cohn and Robert Koch.
• Pasteur’s academic positions were numerous, and his scientific accomplishments earned him France’s highest decoration, the Legion of Honor, as well as election to the Académie des Sciences and many other distinctions.
• Today there are some 30 institutes and an impressive number of hospitals, schools, buildings, and streets that bear his name- a set of honors bestowed on few scientists.

Table of Contents

Interesting Science Videos

Major Contributions of Louis Pasteur

The studies on fermentation led Pasteur to take interest to work in microbiology. His contributions to microbiology are as follows:

• He disproved the theory of spontaneous generation of disease and postulated the germ theory of disease: He stated that disease cannot be caused by bad air or vapor but it is produced by the microorganisms present in air.
• The doctrine of spontaneous generation was disapproved by his experiments that showed that without contamination, microorganisms could not develop. 
• He proposed the principles of fermentation for preservation of food.
• He introduced the sterilization techniques and developed steam sterilizer, hot air oven and autoclave.
• He described the method of pasteurization of milk and wine.
• He reduced mortality from puerperal fever. He had also contributed for the vaccine development against several diseases, such as anthrax, fowl cholera and rabies.
• Liquid media concept: He used nutrient broth to grow microorganisms.
• He was the founder of the Pasteur Institute, Paris.

Besides in microbiology, Pasteur made significant discoveries in chemistry, most notably on the molecular basis for the asymmetry of certain crystals and racemization.

• Early in his career, his investigation of tartaric acid resulted in the first resolution of what is now called optical isomers.
• His work led the way to the current understanding of a fundamental principle in the structure of organic compounds.

Pasteur’s Experiment of the Swan Necked Flask

Figure:  Louis Pasteur’s spontaneous generation experiment illustrates the fact that the spoilage of liquid was caused by particles in the air rather than the air itself. These experiments were important pieces of evidence supporting the idea of germ theory of disease. Source: Wikipedia.

• Pasteur first filtered air through cotton and found that objects resembling plant spores had been trapped. If a piece of cotton was placed in a sterile medium after air had been filtered through it, microbial growth appeared.
• Next he placed nutrient solutions in flasks, heated their necks in a flame, and drew them out into a variety of curves, while keeping the ends of the necks open to the atmosphere. These flasks looked like the neck of swans hence giving the famous experiment its name.
• Pasteur then boiled the solutions for a few minutes and allowed them to cool.
• No growth took place even though the contents of the flasks were exposed to the air.
• Pasteur pointed out that no growth occurred because dust and germs had been trapped on the walls of the curved necks.
• If the necks were broken, growth commenced immediately.
• By this Pasteur proved that all life even microbes arose only from their like and not de novo (germ theory of disease). Pasteur had not only resolved the controversy of origin of microorganisms but also had shown how to keep solutions sterile with this one single experiment.
• Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.
• Sastry A.S. & Bhat S.K. (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers.
• Murray, P. R., Rosenthal, K. S., & Pfaller, M. A. (2013). Medical microbiology. Philadelphia: Elsevier/Saunders
• https://www.britannica.com/biography/Louis-Pasteur/Research-career
• https://www.biography.com/people/louis-pasteur-9434402

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Sagar Aryal

1 thought on “Louis Pasteur and his contributions”

“He proposed the principles of fermentation for preservation of food.” ???

He proposed the principles of pasteurization for preservation of food.

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