ALCOHOLIC FERMENTATION 381 



That phosphate is a necessity for alcoholic fermentation by 

 zymase is generally agreed, but views other than the above 

 have been put forward regarding the part played by it in 

 fermentation. 



Iwanoff,* for instance, considers that the phosphate formed 

 is a triose phosphate, the formation of which is not necessarily 

 accompanied by the evolution of carbon dioxide and alcohol, 

 since the combination will take place when a phosphate is added 

 to the filtrate of a solution of sugar which has been fermented 

 by yeast-extract. He also found that the sugar obtained from 

 the sugar phosphate is not fermented by living yeast. Iwanoff 

 concludes that there are three stages in alcoholic fermentation : 

 the sugar is first broken down into simpler sugars, then by 

 the action of an enzyme, termed synthease, a triose phosphate 

 is organized, which is then acted upon by alcoholase to form 

 carbon dioxide, etc. 



These views are not agreed with by Plarden and Young, •[ 

 who criticize the methods employed by Iwanoff. 



According to Buchner, lactic acid is an intermediate pro- 

 duct of fermentation ; in the first place the glucose under the 

 influence of zymase is converted into lactic acid, which is then 

 attacked by another enzyme, the action giving origin to carbon 

 dioxide and alcohol. 



Kohl,]: however, points out that lactic acid is not fermented 

 by zymase, by compressed yeast nor by bottom yeast ; indeed 

 I per cent lactic acid is sufficient to stop the auto-fermentation 

 of yeast and to reduce greatly the fermentation of glucose. 

 On the other hand, zymase will ferment sodium lactate, which 

 indicates that if lactic acid is an intermediate product of fer- 

 mentation, according to Buchner's view, a salt rather than the 

 acid must be formed. 



In yeast-extract Kohl found an enzyme, catalase, which 

 was capable of oxidizing phenols. The yeast-extract on 

 filtering produces lactic acid in the presence of glucose, and 

 the acid in the presence of zymase is converted into alcohol 

 and carbon dioxide ; if, however, zymase be not present, 

 oxidation may go further and other acids be produced, 



•Iwanoff: "Centrlbl. Bakt.," 1909,24, i. 



t Harden and Young: "Centrlbl, Bakt.," 1910, 26, 178. 



5: Kohl: " Beih. bot. Centrlbl.," 1910, 29, 115, 



