FERMENTS. 



483 



Until recently the whole process of alcoholic fermentation was sur- 

 rounded with great obscurity. E. Buchner and J. Meisenheimer l have 

 succeeded at least in indicating the way in which the decomposi- 

 tion proceeds. Thus, in their cell-free fermentations, they invariably 

 found inactive lactic acid. They concluded that this must be a normal 

 intermediate product, and formulated the alcoholic fermentation to take 

 place as follows: 



OH 

 H 



OH 

 H 



CO 2 

 CH 2 OH 



CH 3 



C0 2 

 CH 2 OH 



i, 



intermediate product lactic acid 

 + 5H 2 



Ethyl alcohol 

 + CO 2 



At all events, alcoholic fermentation is a very complicated process, 

 and the question has now arisen, whether it is to be looked upon as brought 

 about by one or by several ferments. One ferment may convert the sugar 

 into lactic acid, while a second transforms this into alcohol. There are 

 also by-products in the alcoholic fermentations. Glycerol, succinic acid, 

 and acetic acid have been noticed among these. If we employ zymase, 

 such products are not formed to any extent. They are evidently not a 

 part of the alcoholic fermentation itself, but are due to other metabolic 

 changes of the yeast. 2 



1 Ber. 37, 417 (1904). 



2 For the older conception of alcoholic fermentation, cf. C. v. Nageli; Theorie der 

 Gahrung. Munchen (1879). 



