SYNTHESIS IN THE PLANT 



343 



active amyl alcohol respectively, according to the following 

 schemes. 



CH 3 \ 



^ 

 CH 3 / 



CHCH 2 CHNH 2 COOH + H 2 O = 



CH 



CH 



CH 3 / 

 CH 3 \ 



C 2 H 5 / 



CHCH 2 CH 2 OH + CO 2 + NH 3 



Amyl alcohol 

 CHCH 2 OH + CO 2 



NH 3 



Leucine 

 CHCHNH 2 COOH + H 2 O 



Isoleucine Active amyl alcohol 



The amounts of these alcohols produced are proportional 

 to the quantities of leucine or isoleucine added and rise, under 

 favourable conditions, to as much as 7 per cent ; furthermore, 

 it was found that although the leucine parted with its 

 nitrogen in the form of ammonia, the latter substance was not 

 lost, but appeared to be taken up by the yeast in the produc- 

 tion of new protein material ; this observation led to trying 

 the effect of adding ammonium salts, when it was found that 

 the yeast, rinding these latter to be an easier source of 

 nitrogenous food, gave up attacking the leucine, and conse- 

 quently less amyl alcohol was produced. 



These experiments therefore prove that amino acids can 

 be fermented by yeast with the production of alcohols in 

 much the same way as sugars can be fermented. The amino 

 acids of the protein of the yeast cells are the source of the amyl 

 alcohol and succinic acid found among the products of the fer- 

 mentative activity of such living yeast cells. When yeast 

 juice is employed, these by-products are not formed. The 

 practical importance of these discoveries can be gauged from 

 the fact that the production of amyl alcohol or fusel oil by 

 the yeast fermentation of sugar has always been a source of 

 trouble to spirit distillers, necessitating elaborate processes 

 for refining ; these researches have provided both an explana- 

 tion of the cause and a remedy for the evil.* 



Since, moreover, other amino acids besides the leucines are 

 also found to be attacked in a similar way with the production 

 of a number of widely different products, some of which are 



* A knowledge of the cause of the amyl alcohol production is also import- 

 ant from the point of view of increasing the yield of this substance, since large 

 quantities of amyl alcohol are required for the preparation of amyi acetate, used 

 as a flavouring material for confectionery, and as a solvent in the manufacture 

 of varnish, smokeless powder, etc, 



