Yeast and Fermentation

Louis Pasteur: The Father of Fermentation

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

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Louis Pasteur (1822-1895), French chemist and microbiologist. Ca. 1870.

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 micro-organisms in fermentation. Around 1860, he demonstrated that micro-organisms 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 micro-organisms 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 microorganisms 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 micro-organisms 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!

  1. Fenesraz, M. (2021) Fermentation: History, uses, and recipes. Flammarion. 
  2. Ligon, B. Lee (2002). “Biography: Louis Pasteur: A controversial figure in a debate on scientific ethics”. Seminars in Pediatric Infectious Diseases. 13 (2): 134–141. doi:10.1053/spid.2002.125138. PMID 12122952. 
  3. Barnett, James A.; Barnett, Linda (2011). Yeast Research: A Historical Overview. Washington, DC: ASM Press. ISBN 978-1-55581-516-5. 
  4. Zimmermann, F.K.; Entian, K.-D., eds. (1997). Yeast Sugar Metabolism. CRC Press. pp. 20–21. ISBN 978-1-56676-466-7. 
  5. Fenesraz, M. (2021) Fermentation: History, uses, and recipes. Flammarion. 
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