PROPERTIES OF BUCHNER'S ZYMASE 89 



shown that alcohol, carbon dioxide, glycerol, and succinic acid are 

 all formed at the same time; however, these products are always in 

 small quantities. According to this savant, 105.65 grams of glucose 

 yielded the following: 



Ethyl alcohol 51.11 



Carbon dioxide 49 . 42 



Succinic acid . 673 



Glycerol 3.40 



Among the products of fermentation may be found such secondary 

 products as fatty acids, volatile acids, ethyl aldehyde, acetic acid, 

 higher alcohols, ethers, and tyrosine and leucine. Some result from 

 the decomposition of sugars while others are products of excretion 

 from the cell. Glycerol seems to belong to the first category. The 

 volatile acids are probably connected with the nitrogenous metabo- 

 lism (Duclaux, Kruis). According to Ehrlich, it seems to be the same 

 with succinic acid and the higher alcohols. It has been established 

 by Ehrlich that leucine and isoleucine are assimilated by yeasts 

 with the fixation of a molecule of water; they are decomposed into 

 amyl and isoamyl alcohols by the liberation of ammonia which serves 

 the metabolism of the yeasts. The ethers result from the action of 

 acids formed by the action of air or other organisms with ethyl 

 alcohol. As to the presence of aldehydes established by many investi- 

 gators (Roux and Linossier, Duclaux, Roeser), they seem to result 

 from the oxidation of alcohol by air or by the action of the yeasts. 

 The observations of Trillat and Sauton, including those of Kayser and 

 Demolom, have shown that wine yeast; agitated in the presence of air 

 caused a change of a part of the alcohol into aldehydes, ethyl and 

 acetic. The acetic aldehyde is finally oxidized to acetic acid. It then 

 seems as if the yeasts are able to use alcohol which results from 

 fermentation and oxidize it to the aldehyde. 



Character and Properties of Buchner's Zymase 



What is the mechanism by which fermentation is accomplished? 

 In 1858, Berthelot was the first to demonstrate that fermentation 

 was brought about by enzymes secreted by yeasts. Bernard toward 

 1860 objected to this view. Pasteur and Denys Cochin had tried to 

 isolate this enzyme from yeast but their efforts were in vain. Pas- 

 teur without discarding the possibility of an enzyme action thought 

 more and more that fermentation was a vital act of the yeast cell 

 itself. 



It is known that the future has borne out Berthelot's contentions. 

 Buchner, in 1897, succeeded in extracting the zymase from the yeast 



