602 THE GUM FERMENTATION OF SUGAR CANE JUICE, 



the gum, which consisted of a mixture of a dextro-rotatory with 

 an inactive body, might have been derived from the levulose of 

 the inverted saccharose. Boekhout* in investigating the action of 

 Streptococcus ho7'nensis found a laevo-rotatory sugar in the residue 

 from the bacterial fermentation and the gum (dextran) produced 

 a dextro-rotatory sugar on hydrolysis. From these facts he con- 

 cluded that dextrose was the origin of the gum. 



In determining the origin of the gum it is necessary to test 

 the optical activity of the gum and the amount of the residual 

 sugars after the fermentation. This necessitates the use of a 

 polarimeter, and as I had not that instrument in the laboratory 

 I asked Mr. Steel and he consented to do the necessary deter- 

 minations from material which I supplied. Mr. Steel was so 

 interested with the gum that he investigated it very fully in the 

 endeavour to identify it, and his results, which confirm and 

 amplify my work upon the gum, are embodied in a paper which 

 is published simultaneously with this. From it I extract a few 

 notes bearing upon the question of the origin of the gum. 



The gum is Isevorotatory (Aj)= -40°) and the amount of the 

 residual sugars and of the gum show that the latter is formed 

 from the nascent levulose and also from "something else," because 

 the amount of levulose which has disappeared does not equal the 

 gum that is formed. From this we can only conclude that the 

 " something else " must be dextrose. The fact that the gum is 

 l?evorotatory and on hydrolysis yields pure levulose does not con- 

 flict with the levulose-dextrose origin of the gum. Much more 

 levulose than dextrose is utilised in its formation, and it is quite 

 conceivable that the optical activity of the major constituent may 

 influence the rotatory power of the derived gum. We can convert 

 dextrose to levulose by forming phenyl-glucosazone, which upon 

 reduction and subsequent treatment with nitrous acid yields 

 levulose. Since this change can be accomplished in the laboratory 

 by the formation of intermediate compounds, there is no reason 

 why a gum which yields pure levulose on hydrolysis should not 

 have been derived in part (or entirely) from dextrose. 



* Boekhout, Cent. f. Bakt., 2te Abt., vi., 161. 



