ALCOHOLIC FERMENTATION 263 



yeast with sand and submitting the mixture to con- 

 siderable pressure. The expressed juice was capable, 

 in virtue of the enzymes which it contained, of causing 

 the fermentation of sugar with the production of the same 

 products as the living yeast. Since then a number of 

 other yeast preparations have been obtained by various 

 workers, of which zymin (yeast dried with acetone) and 

 " maceration juice," obtained by the autolysis of yeast 

 in water, are the most important. 



The Role of Phosphates in Fermentation. — In 1905 

 Harden and Young established the importance of in- 

 organic phosphates and phosphoric esters in fermentation 

 processes. During an investigation of anti -enzymes 

 Harden had added a serum, prepared by injecting yeast 

 juice into rabbits, to a fermenting sugar solution and 

 found that an increase, and not the expected decrease, 

 of fermentation occurred. Normal serum was found to 

 have the same property. The addition of boiled yeast 

 juice to yeast juice and sugar solution had a similar 

 effect. The cause of the increase in the case of boiled 

 yeast juice was traced to two factors : (a) the presence of 

 inorganic phosphates, and (b) to a heat stable co -enzyme 

 or CO -zymase. In the case of serum the effect was shown 

 to be due to the phosphates present. 



It was found that the addition of inorganic phosphate 

 to fermentations by yeast preparations caused a con- 

 siderable increase in both the rate of fermentation and in 

 the absolute amount of sugar fermented. This increase 

 did not occur on the addition of phosphate to fermenta- 

 tions by living yeasts. The rate of fermentation was 

 measured as the volume of carbon dioxide evolved every 

 five minutes, and it was found that the extra volume 

 of carbon dioxide evolved was proportional (molecule for 

 molecule) to the amount of inorganic phosphate converted 

 into esters. The normal rate of fermentation by yeast 

 juice is about 3 ml. of carbon dioxide per five minutes, 

 represented l)y the straight line (1) in Fig. 7. The rate 



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