isobutyl glycol —0.158* 

 amy 1 alcohol —0.051 

 n-propyl alcohol —0.002 

 isobutyl alcohol —0.0015 



42 PHYSIOLOGY OF BACTERIA 



The general formula for the alcoholic fermentation is 

 C6H12O6 = 2C2H5OH + 2CO2 



Pasteur hesitated to accept this formula because of 

 other compounds found regularly among the fermen- 

 tation products which were not given by the above 

 equation. The following list gives the approximate 

 amounts of products found in normal industrial alcoholic 

 fermentations : 



Table 8. — Products of Alcoholic Fermentation from 100 Parts of 



Sugar 



Alcohol 48 . 4 parts 



CO2 46.5 



Acetic acid 0.05-0.25 



Lactic acid . -0.2 



Fusel oil 0.05-0.35% 



Succinic acid 0.5-0.7 



Glycerol 2.5 -3.6 



Acetaldehyde -0.08 



Furfural traces 



Yeast cells 1.2-5 



Boussignault had the correct conception that in order 

 to establish equations of fermentation processes, it is 

 essential to find out which products are always formed in 

 the same ratio, because only these could derive from the 

 same type of decomposition. 



It was shown much later by Ehrlich that some of these 

 products, though nitrogen-free, derive from protein 

 material. He found (1905) that leucin was the mother 

 substance of iso-amyl alcohol, and that iso-leucin could 

 be converted into optically active amyl alcohol. This 

 was accomplished by a hydrolysis of the amino acid 

 liberating NH3, and by a decarboxylation of the resulting 

 a-hydroxy acid. 



* According to Duclaux III, 434 (1900). The amount of by-products 

 is smaller with yeast juice than with living yeast. 



