340 Messrs. A. Harden and W. J. Young. [June 10, 



IV. Fermentation of Fructose by Yeast-juice in the presence of Phosphate. 



Fructose, like mannose, agrees qualitatively with glucose in its behaviour 

 towards phosphates, but it differs quantitatively from both these sugars in 

 two important respects : (1) The optimum concentration of phosphate is 

 much greater ; (2) the maximum rate of fermentation attainable is much 

 higher. 



These points of resemblance and dissimilarity are brought out by the 

 following experiments : — 



(a) When a phosphate is added to yeast-juice containing fructose the 

 rate of fermentation rises to a maximum and then falls to a rate which is 

 usually slightly higher than the original rate of fermentation. 



Experiment 12.— Ten cubic centimetres of a - 3 molar solution of sodium 

 phosphate were added to a mixture of 25 c.c. of yeast-juice and 1 gramme of 

 fructose, the original rate of fermentation of which was - 8 c.c. in five 

 minutes. The total volume of the mixture was 35"6 c.c. The readings were 

 as follows : — 



Table VI. — Fermentation of Fructose in presence of Phosphate. 



Time after addition 

 of phosphate in 

 minutes. 



Cubic centimetre of 



C0 2 evolved in 

 preceding 5 minutes. 



5 



14 -9 



10 



21 -3 



15 



21 -7 



20 



17 -3 



25 



10 -9 



30 



2-0 



35 



1 5 



40 



1-0 



45 



1-2 



The maximum rate attained varies very considerably with different samples 

 of yeast-juice, as is shown by the following numbers (see Table VII), which 

 refer in each case to 25 c.c. of yeast-juice. 



It is interesting to note that the two high rates, 80 and 76 - 2 c.c. per 

 five minutes, are equal to about half the rate obtainable with an amount of 

 living yeast corresponding to 25 c.c. of yeast-juice, assuming that about 

 40 grammes of yeast are required to yield this amount of juice, and that 

 this amount of yeast would give about 140 c.c. of carbon dioxide per 

 five minutes at 25°, which has been found experimentally to be the average 

 rate obtainable with the top yeast employed for these experiments. 



