206 THE CARBOHYDRATES. 



and then from this by loss of C0 2 the alcohol is derived. The ammonia 

 is assimilated by the yeast. If the amino-acid is in the racemic form 

 then only the one component occurring naturally is transformed into 

 alcohol while the other remains in great part unchanged. In this manner 

 leucine is converted into isoamylalcohol according to the following equa- 

 tion: 



/CH 3 

 HOCO.CH(NH 2 ).CH 2 .CH< +H 2 = 



Leucine X CH 3 



/CH 3 

 NH 3 +C0 2 +HOCH 2 .CH 2 .CH< 



Isoamylalcohol \QH 3 



Other examples of the same kind is the formation of d-amylalcohol 

 from d-isoleucine and of isobutylalcohol from a-amino-valeric acid. 

 The formation of higher alcohols takes place with yeast poor in nitrogen 

 and in the presence of large amounts of sugar. In an analogous man- 

 ner, under the influence of yeast in the presence of sugar and inor- 

 ganic nutritive salts, from tyrosine tyrosol (p-oxyphenylethyl alcohol) 

 HO.C6H4.CH 2 .CH 2 .OH is derived and from tryptophane we get tryptophol 

 (/3-indoxy lethyl alcohol) 1 . 



C.CH 2 .CH 2 OH 



NH 



Other fermentation processes which are brought about by yeast but without 

 the presence of sugar have been studied by NEUBERG 2 and his collaborators. 

 Among these we will mention the decomposition of pyroracemic acid (pyruvic 

 acid) into carbon dioxide and acetaldehyde : 



HO.CO.CO.CH 3 =C0 2 +HOC.CH 3 . 



The enzyme active in this fermentation is called carboxylase. If the pyro- 

 racemic acid exists in the form of an alkali salt then the cleavage takes place ac- 

 cording to the formula, 



2KO.CO.CO.CH 3 +H 2 0=C0 2 +2HOC.CH 3 H-K 2 C0 3 



and alkali carbonate is formed from a neutral salt. In this case the aldehyde 

 is condensed by the alkali to aldol, the first polymerization product of acetaldehyde. 



The previously mentioned (page 41) lactic acid fermentation of 

 various sugars is caused by the action of different varieties of bacteria. 

 The equation represents a cleavage of one hexose molecule into two 

 lactic acid molecules C 6 H] 2 O 6 = 2HOCO.CHCOH) .CH 3 . Nothing positive 



1 Ber. d. d. chem. Gesellsch., 44, 139 (1910); 45, 883 (1912). 



2 Bioch. Zeitschr., 31, 170 (1910); 32, 323; 36, 60, 68, 76 (1911); 47, 405, 413 (1912). 



