ENERGY SUPPLY OF THE CELL 57 



e.g., in the study of cheese ripening. In this chapter 

 deaUng with the equations of fermentation, they are of 

 no special interest. 



The next step in the degradation of proteins is the 

 formation of amino-acids. In a very complete study of 

 the decomposition of casein by B. mesentericus vulgatus, 

 Grimmer and Wiemann (1921) found the following 

 amino-acids: alanin, valin, leucin, tyrosin, aspartic acid, 

 glutamic acid, prolin, arginin, lysin, histidin, trypto- 

 phane, and probably phenylalanin. Of the decomposi- 

 tion products of amino-acids, the following compounds 

 could be identified: putrescin, cadaverin, tryptamin, 

 tjo-osol, ammonia, and probably p. oxybenzoic acid. 

 In the presence of lactose, histamin and 7-amino- 

 but3n:'ic acid were also formed. This is an example of 

 what can be expected in an aerobic decomposition of a 

 protein. 



Fermentations of Amino Acids. — The further decom- 

 position of these amino acids is something quite definite, 

 chemically speaking, and the equations can be given. 

 A good survey of all products derived from amino-acids 

 is given by Stephenson (1930) in tabulated form. 



Perhaps the most common type of decomposition of 

 amino acids is the splitting off of NH3. This can be 

 accomplished in four different ways, namely by hydroly- 

 sis, by reduction, by oxidation and by leaving an unsatu- 

 rated double bond (desaturation) . The liberation of 

 ammonia by hydrolysis has already been described in 

 the formation of alcohols from amino acids by yeast, 

 especially with the amyl alcohol (page 43). Leucin was 

 hydrolyzed to a-hydroxy-caproic acid. 



C4H9-CH(NH2)-C02H + H2O = 



C4H9CH(OH)C02H + NH3 



