Editing Louis Pasteur (section)

=== Fermentation and germ theory of diseases ===

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.<ref>{{cite book|last1=Vallery-Radot|first1=René|translator-last=Devonshire|translator-first=R. L.|title=The Life of Pasteur|date=1919|publisher=Constable & Company|location=London|page=79|url=https://archive.org/stream/in.ernet.dli.2015.173907/2015.173907.The-Life-Of-Pasteur#page/n101/mode/2up}}</ref><ref name=Ligon /> Pasteur began his research in the topic by repeating and confirming works of [[Theodor Schwann]], who demonstrated a decade earlier that yeast were alive.

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.<ref>{{cite book|last1=Vallery-Radot|first1=René|title=La vie de Pasteur|date=1907|publisher=Librairie Hachette|location=Paris|page=98|url=https://archive.org/stream/laviedepasteur01vallgoog#page/n110/mode/2up|language=fr}}</ref> A memoire was subsequently published on 30 November 1857.<ref>{{cite journal|last1=Pasteur|first1=Louis|title=Mémoire sur la fermentation appelée lactique|journal=Comptes Rendus Chimie|year=1857|volume=45|pages=913–916|url=http://gallica.bnf.fr/ark:/12148/bpt6k30026.image.r=+COMPTES+RENDUS+++DES+S%C3%89ANCES+DE+L.f915.langFR|language=fr|access-date=11 March 2017|archive-date=12 March 2017|archive-url=https://web.archive.org/web/20170312141626/http://gallica.bnf.fr/ark:/12148/bpt6k30026.image.r=+COMPTES+RENDUS+++DES+S%C3%89ANCES+DE+L.f915.langFR|url-status=live}}</ref> 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 acid bacteria|lactic yeast]], always present when [[Lactic acid fermentation|sugar becomes lactic acid]]."<ref name=manchester2007>{{cite journal|last1=Manchester|first1=K.L.|title=Louis Pasteur, fermentation, and a rival|journal=South African Journal of Science|year=2007|volume=103|issue=9–10|pages=377–380|url=http://www.scielo.org.za/scielo.php?pid=S0038-23532007000500008&script=sci_arttext|access-date=26 October 2014|archive-date=26 October 2014|archive-url=https://web.archive.org/web/20141026053500/http://www.scielo.org.za/scielo.php?pid=S0038-23532007000500008&script=sci_arttext|url-status=live}}</ref>

This memoir on alcoholic fermentation was published in full form in 1858.<ref>{{cite journal|last1=Pasteur|first1=Louis|title=Nouveaux faits concernant l'histoire de la fermentation alcoolique|journal=Comptes Rendus Chimie|year=1858|volume=47|pages=1011–1013|language=fr}}</ref><ref>{{cite journal|last1=Pasteur|first1=Louis|title=Nouveaux faits concernant l'histoire de la fermentation alcoolique|journal=Annales de Chimie et de Physique |series=3rd Series|year=1858|volume=52|pages=404–418|language=fr}}</ref> [[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.<ref name=Barnett>{{cite book|last1=Barnett|first1=James A.|last2=Barnett|first2=Linda|title=Yeast Research: A Historical Overview|year=2011|publisher=ASM Press|location=Washington, DC|isbn=978-1-55581-516-5|url=https://books.google.com/books?id=ZwisBAAAQBAJ}}</ref> He also demonstrated that, when a different microorganism contaminated the wine, lactic acid was produced, making the wine sour.<ref name=Ligon /> In 1861, Pasteur observed that less sugar fermented per part of yeast when the yeast was exposed to air.<ref name=Barnett /> The lower rate of fermentation aerobically became known as the [[Pasteur effect]].<ref>{{cite book|editor1-last=Zimmermann|editor1-first=F.K.|editor2-last=Entian|editor2-first=K.-D.|title=Yeast Sugar Metabolism|date=1997|publisher=CRC Press|isbn=978-1-56676-466-7|pages=20–21|url=https://books.google.com/books?id=VSQZ1AVg74oC&pg=PA20}}</ref>
[[File:Louis Pasteur experiment.jpg|thumb|left|Pasteur experimenting in his laboratory]]
[[File:LouisPasteurMonumentLille.jpg|thumb|[[Institut Pasteur de Lille]]]]

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&nbsp;°C.<ref name=Bowden /> This killed most bacteria and moulds already present within them. Pasteur and [[Claude Bernard]] completed tests on blood and urine on 20 April 1862.<ref>{{cite book|last1=Vallery-Radot|first1=René|translator-last=Devonshire|translator-first=R.L.|title=The Life of Pasteur|date=1919|publisher=Constable & Company|location=London|page=104|url=https://archive.org/stream/in.ernet.dli.2015.173907/2015.173907.The-Life-Of-Pasteur#page/n125/mode/2up}}</ref> Pasteur patented the process, to fight the "diseases" of wine, in 1865.<ref name=Bowden>{{cite book|last1=Bowden|first1=Mary Ellen|last2=Crow|first2=Amy Beth|last3=Sullivan|first3=Tracy|title=Pharmaceutical achievers: the human face of pharmaceutical research|year=2003|publisher=Chemical Heritage Press|location=Philadelphia|isbn=978-0-941901-30-7|url=https://books.google.com/books?id=4yPPE0xHEmkC&pg=PA6}}</ref> The method became known as [[pasteurization]], and was soon applied to beer and milk.<ref name=Nelson2009>{{cite journal|last1=Nelson|first1=Bryn|title=The Lingering Heat over Pasteurized Milk|journal=Chemical Heritage Magazine|year=2009|volume=27|issue=1|url=https://www.sciencehistory.org/distillations/article/lingering-heat-over-pasteurized-milk|access-date=20 March 2018|archive-date=21 March 2018|archive-url=https://web.archive.org/web/20180321192530/https://www.sciencehistory.org/distillations/article/lingering-heat-over-pasteurized-milk|url-status=live}}</ref>

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.<ref name=Listerine>{{cite journal|last1=Hicks|first1=Jesse|title=A Fresh Breath|url=http://www.chemheritage.org/discover/online-resources/thanks-to-chemistry/listerine.aspx|journal=Chemical Heritage Magazine |access-date=27 January 2015 |url-status=dead |archive-url=https://web.archive.org/web/20160611130657/http://www.chemheritage.org/discover/online-resources/thanks-to-chemistry/listerine.aspx|archive-date=11 June 2016}}</ref>

In 1866, Pasteur published ''Études sur le Vin'', about the diseases of wine, and he published ''Études sur la Bière'' in 1876, concerning the diseases of beer.<ref name=Barnett />

In the early 19th century, [[Agostino Bassi]] had shown that [[muscardine]] was caused by a fungus that infected silkworms.<ref name=Hatcher /> Since 1853, two diseases called ''[[pébrine]]'' and ''[[flacherie]]'' had been infecting great numbers of [[silkworm]]s 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.<ref name=Berche>{{cite journal|last1=Berche|first1=P.|title=Louis Pasteur, from crystals of life to vaccination|journal=Clinical Microbiology and Infection|year=2012|volume=18|issue=s5|pages=1–6|doi=10.1111/j.1469-0691.2012.03945.x|pmid=22882766|doi-access=free}}</ref><ref name="Schwartz">{{cite journal|last1=Schwartz|first1=M.|year=2001|title=The life and works of Louis Pasteur|journal=Journal of Applied Microbiology|volume=91|issue=4|pages=597–601|doi=10.1046/j.1365-2672.2001.01495.x|pmid=11576293|doi-access=|s2cid=39020116}}</ref>

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]]).<ref name=Hatcher>{{cite book|last1=Hatcher|first1=Paul|last2=Battey|first2=Nick|title=Biological Diversity: Exploiters and Exploited|date=2011|publisher=John Wiley & Sons|isbn=978-0-470-97986-0|pages=88–89, 91|url=https://books.google.com/books?id=FpQpedSpeWMC&pg=PA89}}</ref> Pasteur also showed that the disease was hereditary.<ref name="Keim pp. 87-88">{{cite book|last1=Keim|first1=Albert|last2=Lumet|first2=Louis|title=Louis Pasteur|date=1914|publisher=Frederick A. Stokes Company|pages=87–88|url=https://archive.org/stream/louispasteur00keim#page/86/mode/2up}}</ref> 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.<ref>{{cite book|last1=Vallery-Radot|first1=René|translator-last=Devonshire|translator-first=R. L.|title=The Life of Pasteur|date=1919|publisher=Constable & Company|location=London|page=141|url=https://archive.org/stream/in.ernet.dli.2015.173907/2015.173907.The-Life-Of-Pasteur#page/n161/mode/2up}}</ref><ref name="Keim pp. 87-88" /> Pasteur concluded that bacteria caused flacherie. The primary cause is currently thought to be viruses.<ref name=Hatcher /> 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.<ref>{{cite book|last1=Vallery-Radot|first1=René|translator-last=Devonshire|translator-first=R. L.|title=The Life of Pasteur|date=1919|publisher=Constable & Company|location=London|page=156|url=https://archive.org/stream/in.ernet.dli.2015.173907/2015.173907.The-Life-Of-Pasteur#page/n175/mode/2up}}</ref>