ACID PEEMENTATION 155 



yields a greater percentage of laevo acid and is especially 

 distinguished by the fact that nearly 25 per cent, of the weight 

 of mannite fermented appears as ethyl alcohol, or more than 

 twice as much as in the case of the sugars studied. 



The general equation for the decomposition of glucose 

 which may be considered as typical is as follows : — 



2CgHi,0e+H,0 = 2C3He03+C2HA + CAO + 2CO,+2H2 



Harden concludes that the products of the reaction can be 

 referred to the constitution of the fermenting substances. 

 Thus the yield of alcohol depends essentially on the presence 

 of the group, CHgOHCHOH ; this only occurs once in glucose, 

 whose formula it wiU be remembered is 



CH20H(CH0H)-CH0 



On the other hand, mannite contains the alcohol-producing 

 group twice, thus : — 



CH20H-(CHOH),-CH20H 



and consequently is capable of jdelding a greater proportion 

 of alcohol. 



The mechanism of the fermentation of glucose as efEected 

 by B. coli is shown, according to Harden, by the following 

 scheme : — 



CH^OH 



CHOH CH,OH 



CH3-CH2OH + CO2 + H^ 



CHOH CHOH 



I I 



CHOH CHOH = lactic acid, succinic acid, etc. 



I -I 

 CHOH CHOH 



COH CHOH 



I 

 COH 



