212 ORGANIC FOODSTUFFS. 



J, EFFRONT (VIII.) is said to employ a nutrient medium con- 

 taining nitrates as the exclusive source of nitrogen. 



263. Organic Sources of Nitrogen. 



In the worts, mashes, and musts used in practical fermentation, 

 the yeast has not to depend on inorganic sources of nitrogen, but 

 generally has at its disposal an abundance of readily assimilable 

 organic nitrogen compounds. The suitability of a few represen- 

 tatives of this large class will be more closely considered in the 

 following paragraphs. 



Among the amides suitable as nitrogenous foodstuffs, special 

 attention is merited by the acid amide of aspartic acid 



(COOH CH 2 CH.NH 2 COOH) 

 namely, asparagin 



(COOH CH 2 CH.NH 2 CO.NH 2 ), 



this substance playing an important part in the mashes used in 

 practice. It is always formed during the germination of seeds, 

 and is therefore present in malt, and still more abundantly in malt 

 culms. Even potatoes contain appreciable quantities. Finally, 

 in addition to other amides, asparagin is one of the chief forms 

 in which nitrogen occurs in the molasses of beet sugar works ; 

 proteins, on the other hand, being almost entirely excluded or 

 eliminated by the method employed for obtaining the juice from 

 the beet in the diffuser and by the purification process in the 

 saturator. M. HAYDUOK (IV.) recognised asparagin as an 

 excellent source of nitrogen in the nutrition of yeast; and 

 this was confirmed by E. LAURENT (VI.), G. HEINZELMANN(!V.), 

 H. P. WIJSMANN (II.), and others. Yeast is capable of trans- 

 forming asparagin into proteins, a property unshared by the 

 animal organism so far as is known at present. The nitrogen of 

 asparagin (which is worthless as a food for animals) is present 

 in the potatoes made into distillery mash, is recovered in the 

 distillery waste in the form of protein, and imparts to this waste 

 product the character of a concentrated fodder for stall-fed 

 cattle. In an experiment carried out by P. PETIT (II.) with a 

 nutrient medium containing asparagin and ammonium phosphate, 

 it was found that top-fermentation yeast consumed twice as much 

 of the former as was utilised by bottom yeast a difference con- 

 sidered by the author to afford a means of differentiating these 

 two yeasts. According to a comparison instituted by R. Kus- 

 SEROW (I.), on the relative influence of asparagin and peptone as 

 the source of nitrogen in saccharified mineral nutrient solutions, 

 the former substance accelerates fermentation and increases the 

 yeast crop. The observation that when grown with the aid of 

 asparagin, the cells of the sedimental yeast are not cohesive, 



