CHAPTER rX 

 ZYMOLOGY— FERMENTS AND FERMENTATIONS 



1. Introduction. — The terms ferment and enzyme are synonymous. 

 Occasionally the expression "catalytic agent" is used. Unfortunately 

 we are as yet very much in the dark as to the physical and chemic^li 

 nature of ferments or enzymes as well as the processes comprehended 

 under the term fermentation. The Hterature on the subject is dis- 

 couragingly voluminous and correspondingly lacking in clearness and 

 conclusiveness. Of the comparatively recent works, that by Oppen- 

 heimer^ is the clearest and in many respects the most complete. In the 

 following presentation of this subject we have followed this author quite 

 closely. 



2. Historical. — As comprehended by the ancients fermentation meant 

 a "boiUng" without fire, a "bubbling" a disturbance in organic compounds 

 resulting in a marked change in the appearance of the substance affected. 

 Originally the term .applied almost wholly to the activities of the yeast 

 organisms. AlcohoUc fermentation was known to the ancient Hindus, 

 Arabians, Greeks and Romans. Centuries prior to the Christian era 

 the Goths, Franks and Teutons made fermented drinks from grain (beer) 

 and honey (mead). 



It is noteworthy that no attempts were made to explain fermentation 

 until comparatively recent times. Valentinus (of Erfurt), as late as the 

 fifteenth century, was among the first to offer an explanation, stating that 

 it was a process of purification, probably getting the idea from the fact 

 that in beer and wine fermentation the liquids become quite clear through 

 the settling of the yeast as soon as the process of fermentation is completed. 

 In fact not until the eighteenth century did the subject receive any special 

 attention on the part of chemists, biologists and physiologists. At first 

 there was a tendency to include under fermentation all of the processes or 

 reactions accompanied by visible gas formation or bubbling, and the 

 hberation of odoriferous substances. Putrefaction and fermentation were 

 considered synonymous. The causes of fermentation were supposed to be 

 mysterious vital forces or energies rendered active under special conditions 

 of light, temperature, air supply and contact stimuli. Gradually distinc- 

 tions were drawn between "spirituous" or vinous (alcoholic) fermentation, 

 "sour" (acid or vinegar) fermentation, and putrefaction. Stahl, and 

 ' Carl Oppenheimee. Die Fermente und Ihre Wirkungen. Leipzig, i goo. 



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