38 PHYSIOLOGY OF BACTERIA 



Alcohol-oxydase. — The efforts of Buchner and Meisen- 

 heimer (1903) to obtain from ground vinegar bacteria 

 an enzyme which would oxidize alcohol to acetic acid 

 were without success. Treatment of vinegar bacteria 

 with acetone gave, however, dead cells which would 

 convert alcohol to acetic acid to a small extent. This 

 was confirmed later by Rothenbach and Eberlein (1905). 

 Buchner and Gaunt (1906) gave more detail regarding 

 this enzyme. The enzyme nature of this fermentation 

 seems to be established, but the enzyme itself appears to 

 be even more sensitive than the alcoholase. 



(c) COMPLEXITY OF ZYMASE ACTION 



The enzyme content of the yeast cell is not limited 

 to the alcoholase. Almost simultaneously with the 

 alcoholase, the endotryptase was discovered, a pro- 

 teolytic enzyme which can liquefy gelatin. This proves 

 its nature as endo-enzyme since living yeast cells of the 

 Saccharomyces type do not attack gelatin. This enzyme 

 gradually destroys the alcoholase, especially in the 

 absence of sugar. 



The alcoholase requires special conditions for its 

 action. An essential factor is the presence of phosphate. 

 Ordinarily, the cell juice of the yeast contains enough 

 phosphate to bring about a visible fermentation, but 

 the addition of phosphate often accelerates the reaction 

 greatly and increases the total production of CO2. 

 It is generally assumed that the alcoholase does not 

 act upon the glucose molecule directly, but upon the 

 hexose-phosphate, a phosphoric acid ester of the sugar. 

 Probably, an enzyme of the yeast brings about the 

 esterification. 



Another essential substance is the so-called co-enzyme 

 of alcoholic fermentation. It was observed that heated 



