Chemical changes brought about by yeast and other forms of cell life, including bacteria, in suitable media, but directly due to enzymes, which are produced by or contained in the living cells. The act of fermentation is generally accompanied with liberation of gas and the evolution of heat. east cells, for example, or an extract prepared from them, but free from the living cells, contain zymase, an enzyme which breaks up sugar to the extent of about 95 per cent, into alcohol and carbon dioxide A medicinal preparation known as zymine is now made by the extraction of moist yeast cells with acetone, and, while it is quite incapable of growth or reproduction, it is much more active in inducing fermentation than the} are. The most favourable temperature for fermentation is from 25 degrees to 30 degrees C., and living yeast cells are killed when the alcoholic strength of the product reaches about 14 percent. The lactic fermentation or souring of milk, is induced by a bacterium known as the Bacterium lactis, but it a mixed fermentat

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Definition of  FERMENTATIONS