page_title: Louis Pasteur
section_title: Fermentation and germ theory of diseases
hierarchical_section_title: Louis Pasteur / Research / Fermentation and germ theory of diseases
caption_attribution_description: English: On the same monument (made at the foot of the façade of the building of the Pasteur Institute of Lille in northern France), are two bronze plaques, respectively the lower level and upper stone monument bearing a bust of Louis Pasteur (white marble) the first one says&#160;: "Tribute members of the association of chemists and sugar distilleries in congress meeting in Lille on 8, 9 and 10 July 1901" («Hommage des membres de l'association des chimistes de sucreries et distilleries réunis en congrès à Lille les 8, 9 et 10 juillet 1901»). It is a commemorative plaque offered to Louis Pasteur by the regional industry of the brewery in 1901&#160;; the second one says&#160;: The company vets ot north to North Louis Pasteur, 1922 (La société des vétérinaires du Nord à Louis Pasteur, 1922) Français&#160;: Sur un même monument (disposé au pied de la façade du bâtiment de l'institut Pasteur de Lille, dans le Nord de la France), figurent deux plaques de bronze, respectivement au niveau inférieur et supérieur du monument de pierre supportant un buste de Louis Pasteur (en marbre blanc) Hommage des membres de l'association des chimistes de sucreries et distilleries réunis en congrès à Lille les 8, 9 et 10 juillet 1901. Plaque commémorative offerte en hommage à Louis Pasteur par l'industrie régionale de la brasserie en 1901 La société des vétérinaires du Nord à Louis Pasteur, 1922
context_page_description: Louis Pasteur was a French biologist, microbiologist, and chemist 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, and his discoveries have saved many lives ever since. He reduced mortality from puerperal fever and created the first vaccines for rabies and anthrax.
  His medical discoveries provided direct support for the germ theory of disease and its application in clinical medicine. He is best known to the general public for his invention of the technique of treating milk and wine to stop bacterial contamination, a process now called pasteurization. He is regarded as one of the three main founders of bacteriology, together with Ferdinand Cohn and Robert Koch, and is popularly known as the "father of microbiology".
  Pasteur was responsible for disproving the doctrine of spontaneous generation. He performed experiments that showed that, without contamination, microorganisms could not develop.
context_section_description: Pasteur was motivated to investigate fermentation while working at Lille. In 1856 a local wine manufacturer, M. Bigot, whose son was one of Pasteur's students, sought for his advice on the problems of making beetroot alcohol and souring.
  According to his son-in-law, René Vallery-Radot, in August 1857 Pasteur sent a paper about lactic acid fermentation to the Société des Sciences de Lille, but the paper was read three months later. A memoire was subsequently published on November 30, 1857. In the memoir, he developed his ideas stating that: "I intend to establish that, just as there is an alcoholic ferment, the yeast of beer, which is found everywhere that sugar is decomposed into alcohol and carbonic acid, so also there is a particular ferment, a lactic yeast, always present when sugar becomes lactic acid."
  Pasteur also wrote about alcoholic fermentation. It was published in full form in 1858. Jöns Jacob Berzelius and Justus von Liebig had proposed the theory that fermentation was caused by decomposition. Pasteur demonstrated that this theory was incorrect, and that yeast was responsible for fermentation to produce alcohol from sugar. He also demonstrated that, when a different microorganism contaminated the wine, lactic acid was produced, making the wine sour. In 1861, Pasteur observed that less sugar fermented per part of yeast when the yeast was exposed to air. The lower rate of fermentation aerobically became known as the Pasteur effect.
  Pasteur's research also showed that the growth of micro-organisms was responsible for spoiling beverages, such as beer, wine and milk. With this established, he invented a process in which liquids such as milk were heated to a temperature between 60 and 100 °C. This killed most bacteria and moulds already present within them. Pasteur and Claude Bernard completed tests on blood and urine on April 20, 1862. Pasteur patented the process, to fight the "diseases" of wine, in 1865. The method became known as pasteurization, and was soon applied to beer and milk.
  Beverage contamination led Pasteur to the idea that micro-organisms infecting animals and humans cause disease. He proposed preventing the entry of micro-organisms into the human body, leading Joseph Lister to develop antiseptic methods in surgery.
  In 1866, Pasteur published Etudes sur le Vin, about the diseases of wine, and he published Etudes sur la Bière in 1876, concerning the diseases of beer.
  In the early 19th century, Agostino Bassi had shown that muscardine was caused by a fungus that infected silkworms. Since 1853, two diseases called pébrine and flacherie had been infecting great numbers of silkworms in southern France, and by 1865 they were causing huge losses to farmers. In 1865, Pasteur went to Alès and worked for five years until 1870.
  Silkworms with pébrine were covered in corpuscles. In the first three years, Pasteur thought that the corpuscles were a symptom of the disease. In 1870, he concluded that the corpuscles were the cause of pébrine (it is now known that the cause is a microsporidian). Pasteur also showed that the disease was hereditary. Pasteur developed a system to prevent pébrine: after the female moths laid their eggs, the moths were turned into a pulp. The pulp was examined with a microscope, and if corpuscles were observed, the eggs were destroyed. Pasteur concluded that bacteria caused flacherie. The primary cause is currently thought to be viruses. The spread of flacherie could be accidental or hereditary. Hygiene could be used to prevent accidental flacherie. Moths whose digestive cavities did not contain the microorganisms causing flacherie were used to lay eggs, preventing hereditary flacherie.
caption: Institut Pasteur de Lille
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