74 PHYSIOLOGY OF YEASTS 



take nitrogen. Compounds with long hydrocarbon chains were easily 

 assimilated. The ring structures, such as histidine, were used with 

 more difficulty. Leucine, adenine, and lysine were easily assimilated, 

 but thymine, uracil, choline, hypoxanthine more difficultly. Adenine, 

 since its nitrogen is in the side chain, was more easily assimilated 

 than hypoxanthine. The more aerobic yeasts were found to utilize 

 more difficultly assimilable nitrogen more easily. 



Zalesky and Israelsky 1 found that the protein content of yeast 

 remained constant in fermentation. Asparagin and glutamic acid 

 support synthesis of protein while glycocoll and phenylalanine do not. 



Thomas 2 and Kolodziejska 3 found two new proteins in yeasts. 

 One belonged to the casein group and the other to the vegetable al- 

 bumins. This latter was named cerevisin. 



Meisenheimer 4 studied nitrogen substance in yeast by autolysis 

 in presence of toluene. All of the common amino acids were found 

 among the cleavage products of yeast protein. Glucosamine, so 

 often looked for in vain, was demonstrated to be present. Nitrogen 

 in yeast protein is distributed as follows: 



Ammonia nitrogen 11 per cent 



Alloxur bases (nuclein bases) nitrogen 7 per cent 



Arginine-histidine nitrogen 22 per cent 



Lysine-choline nitrogen 4 per cent 



Monoamino acid nitrogen 56 per cent 



Haydruck 6 has shown that yeasts are suitable foods and that 

 they should be looked upon favorably as constituents in the human 

 diet. 



Ehrlich 6 has stated that amino acids are deaminized and the rest 

 of the molecule is discharged as fatty acid or alcohols. Sugar is said 

 to be the sole source of carbon. To secure data with regard to what 

 products in sugar decomposition went to make up the complex yeast 

 proteins, he grew Willia anomala, Hansen, in solutions containing 

 only mineral salts, tyrosine and either glycerol, ethyl alcohol, methyl 



1 Zalesky, W. and Israelsky, W. Synthesis of protein in yeast. Ber. deut. 

 Bot. Ges. 32 (1914), 472-9. 



2 Thomas, P. Protein substances of yeast. Comp. rend. Acad. Sci. 156, 

 2024-7. 



3 Thomas, P. and Kolodziejska, S. Protein matter of yeast and its products 

 of hydrolysis. Comp. rend. Acad. Sci. 157, 243-6. 



4 Meisenheimer, J. The nitrogenous substance of yeast. Wochenschr. Brau. 

 32 (1915) 325-6. 



5 Haydruck, F. The utilization of yeasts. Brewers Journal, 48, 57-58. 

 1912. 



6 Ehrlich, F. The formation of the plasma in yeasts and molds. Biochem. 

 Z. 36, 447-97; Chem. Absts. 6 (1912) 240. 



