1909.] 



The Alcoholic Ferment of Yeast-juice. 



343 



Table IX. — Optimum Concentrations of Phosphate and Maximum Eates 

 of Fermentation for Fructose and Glucose. 



No. of 

 6 xp g rime n t . 



Sugar, in 

 crrflTmnftS 



Total 

 "volume 



Optimum volume of 

 - 6 molar phosphate. 



Maximum rate in cubic 

 centimetres of C0 2 per 

 5 minutes. 



Glucose. 



Fructose. 



Glucose. 



Fructose. 



22 



2 



35 



2 



5 



7-5 



32 -2 



23 



4 



50 



1 



10 



5-4 



28 -4 



24 



1-6 



23 



2 



5 



8 



17 



25 



1 



25 



1-75 



5 



5-2 



25 -9 



26 



2 



25 



5 



7-5 



16 -2 



31-2 



27 



2 



20 



2 



3 '5 



7-9 



22 -6 



28 



2 



22 -5 



0-75 



2 



3-4 



22 2 



V. Effect of the Addition of Fructose on the Fermentation of Glucose or 

 Mannose in presence of a large Excess of Phosphate. 



When the rate of fermentation of glucose or mannose by yeast-juice is 

 greatly lowered by the presence of a large excess of phosphate, the addition 

 of a relatively small amount of fructose causes rapid fermentation to occur. 

 This induced activity is not due solely to the fermentation of the added 

 fructose, since the amount of this sugar may be insufficient to yield the gas 

 evolved. 



The general nature of this phenomenon may be gathered from the following 

 experiment : — 



Experiment 29. — Two quantities of 25 c.c. of yeast-juice + 2 grammes 

 glucose + 20 c.c. of - 6 molar K2HPO4 solution + toluene were incubated at 

 25°. The amount of phosphate was largely in excess of the optimum, and 

 the rate of fermentation was found to be 1*8 c.c. per five minutes. 



A. To one of these were added 1 c.c. of glucose solution containing 

 0"2 gramme of the sugar, and 4 c.c. of the phosphate solution. The rate of 

 fermentation fell to 1*5 and continued at this value. 



B. To the other were added 1 c.c. of a solution containing 02 gramme of 

 fructose and 4 c.c. of the phosphate solution. The rate of fermentation at 

 once rose, as shown by the following readings. 



As the evolution of carbon dioxide proceeds the phosphate is converted 

 into hexosephosphate, and its effect on the fermentation of the glucose 

 lessened, and hence in order to maintain the original concentration of 

 phosphate it is necessary to add a fresh quantity at intervals to B, the 

 amount required being calculated from the gas evolved, 13*5 c.c. of CO2 at 



