<P> In 1837, Charles Cagniard de la Tour, Theodor Schwann and Friedrich Traugott Kützing independently published papers concluding, as a result of microscopic investigations, that yeast is a living organism that reproduces by budding . Schwann boiled grape juice to kill the yeast and found that no fermentation would occur until new yeast was added . However, a lot of chemists, including Antoine Lavoisier, continued to view fermentation as a simple chemical reaction and rejected the notion that living organisms could be involved . This was seen as a reversion to vitalism, and was lampooned in an anonymous publication by Justus von Liebig and Friedrich Wöhler . </P> <P> The turning point came when Louis Pasteur (1822--1895), during the 1850s and 1860s, repeated Schwann's experiments and showed that fermentation is initiated by living organisms in a series of investigations . In 1857, Pasteur showed that lactic acid fermentation is caused by living organisms . In 1860, he demonstrated that bacteria cause souring in milk, a process formerly thought to be merely a chemical change, and his work in identifying the role of microorganisms in food spoilage led to the process of pasteurization . In 1877, working to improve the French brewing industry, Pasteur published his famous paper on fermentation, "Etudes sur la Bière", which was translated into English in 1879 as "Studies on fermentation". He defined fermentation (incorrectly) as "Life without air", but correctly showed that specific types of microorganisms cause specific types of fermentations and specific end - products . </P> <P> Although showing fermentation to be the result of the action of living microorganisms was a breakthrough, it did not explain the basic nature of the fermentation process, or prove that it is caused by the microorganisms that appear to be always present . Many scientists, including Pasteur, had unsuccessfully attempted to extract the fermentation enzyme from yeast . Success came in 1897 when the German chemist Eduard Buechner ground up yeast, extracted a juice from them, then found to his amazement that this "dead" liquid would ferment a sugar solution, forming carbon dioxide and alcohol much like living yeasts . Buechner's results are considered to mark the birth of biochemistry . The "unorganized ferments" behaved just like the organized ones . From that time on, the term enzyme came to be applied to all ferments . It was then understood that fermentation is caused by enzymes that are produced by microorganisms . In 1907, Buechner won the Nobel Prize in chemistry for his work . </P> <P> Advances in microbiology and fermentation technology have continued steadily up until the present . For example, in the 1930s, it was discovered that microorganisms could be mutated with physical and chemical treatments to be higher - yielding, faster - growing, tolerant of less oxygen, and able to use a more concentrated medium . Strain selection and hybridization developed as well, affecting most modern food fermentations . </P>

Where does the process of fermentation take place