The Alcoholic Ferment of Yeast-juice. 337 



Table I. — Eelative Eates of Fermentation of Glucose, Mannose, and 

 Fructose by Yeast-juice. 



No. 

 of 

 exp. 



Amount 

 of 

 sugar. 



Total 

 volume. 



Time 



in 

 mins. 



Rate of fermentation. 

 Cubic centimetres evolved 

 in the time given. 



Ratio of rates. 



Glucose. 



Mannose. 



Fructose. 



Glucose. 



Mannose. 



Fructose. 



1 



1 



25 -6 



45 



3 2 



3 



5-3 



1 



0-94 



1 -66 



2 



1 



25 -6 



60 



24 "8 



28 



29 



1 



1-13 



1 -17 



3a 



4 



45 



35 



6-8 



7-2 



8-7 



1 



1 -06 



1 -28 



b 



4 



45 



60 



10 -4 



11 



14 -1 



1 



1 -06 



1 36 



c 



4 



45 



265 



40-2 



38 -6 



46 -9 



1 



0-96 



1-17 



4 



1 -5 



32 -5 



135 



51 -8 



55 -9 



55 -7 



1 



1 -08 



1 -08 



II. Total Fermentation. 



The total weight of carbon dioxide evolved from an excess of the sugar by 

 a given volume of yeast-juice was also found to be slightly greater with 

 fructose than with glucose, whilst that evolved from mannose in the only two 

 experiments made was considerably less than from glucose. 



The following are the experimental results, 'lb c.c. of yeast-juice being 

 employed, and the incubation continued until fermentation had ceased : — 



Table II. — Total Fermentation of Glucose, Mannose, and Fructose. 



No. 

 of 

 exp. 



Sugar 

 added. 



Total 



Total carbon dioxide in grammes. 



Ratio of totals. 



volume. 



Glucose. 



Mannose. 



Fructose. 



Glucose. 



Mannose. 



Fructose. 



5 



4 



32 5 



-6556 



-4452 



-7436 



1 



0-68 



1 -13 



6 



4 



32 -5 



0-7405 



-6226 



-8624 



1 



0-67 



1 -16 



III. Fermentation of Mannose by Yeast-juice in presence of Phosphate. 



Mannose behaves towards phosphates in the presence of yeast-juice in 

 precisely the same manner as glucose.* A rapid rise in the rate of fermenta- 

 tion occurs ; an extra amount of carbon dioxide and alcohol are produced 

 which are equivalent to the phosphate added, and the phosphate is converted 

 into a hexosephosphate which is not precipitable by magnesium citrate 

 mixture and can be isolated in the form of a lead salt. As in the case of 

 glucose, an optimum concentration of phosphate exists at which a maximum 

 rate of fermentation occurs. Beyond this optimum, increase of concentration 



* Harden and Young, loc. cit. 



