204 THE CARBOHYDRATES. 



the hexose group, and in fact all the hexoses do not ferment, and they 

 do not all ferment with the same readiness. d-Glucose and d-mannose 

 ferment readily, but d-galactose only with difficulty. The /-forms of 

 the above-mentioned sugars do not ferment, and from the racemic forms 

 of these sugars the optical Z-antipode can be prepared by the fermenta- 

 tion of the d-sugar. Among the ketoses the d-fructose ferments while 

 the sorbose does not. Among the sugars containing nine atoms of car- 

 bon, the nonoses, the mannonose ferments while the glucononose does 

 not. In regard to the fermentability of the triose, dioxy acetone, see 

 page 205. The different behavior of the various sugars with yeast stands 

 in fixed relation to their configuration, and is not only of great importance 

 for the behavior of the sugar in lower organisms, but also for their behavior 

 in higher developed organisms. Thus the investigations of NEUBERG 

 WOHLGEMUTH l upon arabinose and of NEUBERG and MAYER 2 on man- 

 noses have shown that in rabbits the Z-arabinose and the d-mannose are 

 much better utilized than d- and r-arabinose or I- and r-mannose. See 

 also pages 61-62. 



In the alcoholic fermentation the sugar is decomposed according 

 to the general equation C6Hi206 = 2C2H6O+2C02. The exact process 

 is not clear, and seems to be rather complicated. On page 52 it has 

 been mentioned that for the action of the fermentation enzymes the 

 presence of a dialyzable substance present .in the press-juice is neces- 

 sary (HARDEN and YOUNG 3 ). On the other hand the fermentation 

 power of the press-juice can also be considerably increased by the addi- 

 tion of secondary sodium phosphate. The phosphoric acid in the press- 

 juice after fermentation is only partly precipitable with magnesia mixture 

 (HARDEN and YOUNG). The most favorable action of boiled press- 

 juice is inhibited by lipase (BUCHNER and KLATTE). According to 

 HARDEN and YOUNG we must consider the action of boiled press-juice 

 and of phosphate in that first a hexose-phosphoric acid ester is produced 

 with the simultaneous formation of carbon dioxide and alcohol, according 

 to the following formula: 



The hexose phosphate can then be split into hexose and phosphate 

 by a special enzyme. The hexose phosphoric acid has been isolated 

 as a lead salt by YOUNG. Glucose, fructose and mannose produce in 

 their fermentation the same hexose phosphoric acid. According to 



1 Zeitschr. f. physiol. Chem., 35.' 

 *Ibid., 37. 



3 Literature in Harden and Young, Bioch. Zeitschr., 32, 173 (1911) as well as 

 Buchner and Klatte, ibid., 8, 520 (1908). 



