336 



The Alcoholic Ferment of Yeast-juice. Part IV. — The Fer- 

 mentation of Glucose, Mannose, and Fructose by Yeast-juice. 



By Arthur Harden, F.E.S., and W. J. Young. 

 (Received June 10, — Read June 24, 1909.) 



The results previously communicated by the authors* were obtained 

 exclusively with glucose, and in the present paper an account is given of 

 the behaviour of mannose and fructose towards yeast-juice both in the 

 presence and absence of added phosphate. 



Buchner examined the fermentation of fructose by yeast-juice and found 

 that it proceeded at precisely the same rate as that of glucose.f No experi- 

 ments with mannose appear to have been previously performed. 



The fructose employed throughout these experiments was Kahlbaum's 

 crystallised fructose prepared from inulin. The mannose was prepared by 

 the hydrolysis of ivory-nut and was purified by conversion into the phenyl- 

 hydrazone, which was recrystallised from hot water and was finally decomposed 

 by benzaldehyde in the usual manner.* All the experiments were performed 

 at 25° in the presence of toluene. 



T. Relative Rates of Fermentation of Glucose, Mannose, and Fructose. 



Both mannose and fructose are freely fermented by yeast-juice, as they are 

 also by living yeast. The relative rates of fermentation of these three sugars 

 by yeast-juice vary somewhat in different experiments, but on the average of 

 the experiments performed the fructose appears to be fermented rather more 

 quickly than either mannose or glucose, whilst the mannose is also fermented 

 slightly more rapidly than glucose. 



Table I gives the experimental results, 25 c.c. of yeast-juice being employed 

 in each case. 



In experiments 1, 2, and 4 the rates were taken after the mixture had 

 been incubated for about half an hour. In experiment 3, observations of 

 rate were made during three different intervals, and the time during which 

 the mixture had been incubated before the commencement of each of these 

 was — (a) 25 minutes, (b) 70 minutes, (c) 130 minutes. 



* ' Roy. Soc. Proc.,' B, 1906, vol. 77, p. 405 ; 1908, vol. 80, p. 299. 

 t ' Die Zymasegarung,' p. 100. 



J Herzfeld, ' Ber. Deutsch. Chem. Ges.,' 1895, vol. 28, p. 440. 



