1923] 



KLOTZ — NITROGEN METABOLISM IN FUNGI 



319 



cases to result in a lowering of the N coefficient of the yeast, 

 even in the presence of an abundance of N. The final N coef- 

 ficient of the yeast was found to be independent of the initial 

 coefficient for the particular conditions of reproduction. 



A non-volatile acid, thought to be malic, resulted from the 

 action of yeast on asparagin. Malic acid itself was not ferment- 

 able; but its NH< salt was entirely decomposed, producing 

 CjH 6 OH. Propionic acid, which, according to Effront, results 

 from the action of amidases on asparagin, was not fermented and 

 its NH< salt only slightly attacked. Fermentation was found to 

 be necessary to the assimilation of N, yet the two processes were 

 not proportional, for deamidization was retarded during ex- 

 cessive zymatic action and sometimes continued after this had 

 ceased. Excretion of N into the medium also was found to be 

 conditioned by fermentation, but not proportional to it; it was, 

 however, directly proportional to the sugar present. The 



i 



process took place simultaneously with N assimilation, indicating 

 that excretion was interrelated with the life of the cell ; and the N 

 excreted was shown to be utilizable under certain conditions. 



Iwanoff ('21) pointed out the defects of the Stutzer method, 

 as used in the determination of the protein N, of fermenting 

 fluids; nitrogenous bodies having no protein character were 

 found to be precipitated by the Cu(OH),. These bodies were 

 huminose in character and resulted from the reaction of sugar 

 with an N-containing substance coming from the yeast. These 

 huminose compounds plus alcohol and the other products of 

 fermentation arrested protein decomposition more than did al- 



cohol of the strength present in the fermenting liquid, but it 

 was thought that the acids present were largely responsible for 

 the difference. Alcohol, however, was found to be the chief 

 inhibitor of all the fermentation products, 7 per cent strongly 



inhibiting the protein decomposition. The addition of KH 2 P0 4 



tended to annul this. As a possible explanation of Iwanoff's 

 huminose compounds Gortner and Holm ('17) have shown that 

 the dark nitrogenous substance, "humin" N, formed during the 

 acid hydrolysis of proteins is due to the action of an aldehyde on 

 the indole group of tryptophane. 



Haenseler ('21) found that the yield in dry weight of Aspergillus 





