CHAPTER XV 



FERMENTATION OP CAEBOHYDEATES— ALCOHOLIC FEE- 

 MENTATION IN FOODS— COMMEECIAL PEODUCTION OF 

 ETHYL ALCHOL— FUSEL OILS 



One of the commonest and most important of the changes 

 brought about in carbohydrates by microorganisms is that 

 known as alcoholic fermentation, that is, the transformation 

 of monosaccharides into ethyl alcohol and carbon dioxide. 

 This type of fermentation is important in the preparation 

 of certain beverages, in the manufacture of distilled liquors, 

 and particularly in the preparation of commercial alcohol, 

 bread and other foods. Inasmuch as yeasts are the most 

 active of the organisms in bringing about alcoholic fermenta- 

 tion, consideration of the preparation of commercial yeasts 

 is of importance. 



Agencies Active in Alcoholic Fermentation. — ^A few 

 bacteria are known which may produce alcohol in the 

 process of fermentation. The amounts formed, however, 

 are small, both actually and relatively to the amounts of 

 other fermentative products. Certain species of molds, par- 

 ticularly when grown in sugar solutions under anaerobic 

 conditions, can produce somewhat larger amounts of alco- 

 hol. From a practical point of view, however, all alcohohc 

 fermentation of importance is brought about by members of 

 the yeast genus SaccJiaromyces. 



The transformation of sugar into alcohol and carbon 

 dioxide may be represented by the equation : 



CjHijOs = 2C2H,OH -f 2OO2 

 Dextrose Ethyl alcohol 



The intracellular enzyme zymase has been found capable 



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