The fermentation of beer was caused by yeast present in the environment, predominantly the saccharomyces cerevisiae. Fermentation refers to the procedure of converting the glucose into ethyl alcohol and carbon dioxide gas, which are responsible for the beer's carbonation and its alcohol content. Nowadays, this practice has been largely substituted by the use of highly cultured isolates, such as the saccharomyces carlsbergensis, named after the Carlsberg brand's brewery in Copenhagen, Denmark.
Similar to beer, wine needs yeast during its fermentation process and some of the most elegant wineries still use naturally occurring yeasts. In Champagne and other sparkling wines, the bubbles are actually trapped carbon dioxide, derived from the yeast's fermentation of sugars in the grape juice. Saccharomyces cerevisiae and saccharomyces bayanus are the two types of yeast used during the wine's fermentation process.
In bread production, a different strain of saccharomyces cerevisiae causes the bread to rise. The bread-making strain is specifically selected, as it produces more carbon dioxide and much less alcohol, which evaporates during baking after all. According to Tom Volk and Anne Galbraith from the University of Wisconsin, the use of yeast in bread started in antiquity, when naturally occurring yeast used to contaminate flour, which turned out to be the ingredient of a much more pleasant bread.
A special fungus called saccharomyces boulardii (named after French scientist Henry Boulard who discovered it) is used concurrently with antibiotic therapy to tackle diarrhea on several occasions, such as infectious, antibiotic-associated and HIV-associated diarrhea. It is also appropriate for children and travellers, as well as in treating amoebic dysentery and inflammatory bowel disease. One of the brand names by which saccharomyces boulardii is available in the market is Florastor.