1906.] 



The Alcoholic Ferment of Yeast-juice. 



377 



(2) Disappearance of the Coferment from Yeast-jtiice during Fermentation and 



Autolysis. 



When a small amount of boiled yeast-juice is added to a solution of the 

 inactive residue in 10-per-cent. glucose solution, fermentation commences 

 and continues for a period which varies with the amount added. The 

 cessation of fermentation appears in such a ease to be due to some change 

 in the coferment, since the addition of a further quantity of boiled yeast- 

 juice again sets up fermentation, and if the quantity of boiled juice added 

 on each occasion be small enough, this process can be repeated a third time. 



The following experiments, made at 26° in presence of toluene, illustrate 

 this point : — 



1. One gramme of dry inactive residue was dissolved in 15 c.c. of 

 10-per-cent. glucose solution, and three quantities of 3 c.c. of boiled juice 

 were then successively added, the fermentation being allowed to come to an 

 end before each addition. 



Carbon dioxide evolved. 



1st addition 8 - 2 c.c. 



2nd „ 6 



3rd „ 6 „ 



2. Two grammes of dry inactive residue were dissolved in 15 c.c. of 

 10-per-cent. glucose solution, and two quantities of 15 c.c. of a diluted boiled 

 juice containing 10 per cent, of glucose were successively added. 



Carbon dioxide evolved. 

 1st addition 54 c.c. 



2nd „ 41-2 „ 



This phenomenon has been frequently observed in the course of experi- 

 ments on the filtration of the juice through the Martin filter. The first 

 residue obtained is generally slightly active, and produces a small amount 

 of fermentation with glucose solution. The evolution of carbon dioxide, 

 however, soon stops, but is again renewed when boiled yeast-juice is added. 

 One instance of this was quoted in our previous communication,* and many 

 more have been observed, some of which are tabulated below. 



Carbon dioxide evolved 

 from residue + glucose. 



Boiled juice added. 



Subsequent evolution 

 of carbon dioxide. 



c.c. 



c.c. 



c.c. 



8-6 



20 



72 



13 2 



16 



364-3 



16 -4 



20 



368-8 



* Loc. cit., p. 410. 



