METABOLIC PRODUCTS 



271 



appears to be the carbon-nitrogen ratio. As long as an adequate supply 

 of nitrogen is present, little fat is synthesized. If the carbohydrate sup- 

 ply is high when the nitrogen is exhausted, assimilable fat is synthesized. 

 Linder (1922) termed these two phases 'protein generation and Jat genera- 

 tion. Fat-laden cells of many fungi appear to be incapable of cell division. 

 Fat formation takes place only in the presence of an abundant supply 

 of oxygen. The relation between sugar concentration and amount of fat 

 synthesized by Penicillium javanicum is illustrated in Fig. 52. 



C7> 



3» 



E 



200 



300 400 



Groms of glucose per liter 



500 



Fig. 52. The effect of the concentration of glucose on the amount of mycelium and 

 amount of fat synthesized by PenicilUum javanimm cultured in 75 ml. of medium for 

 12 days. (Drawn from the data of Lockwood, Catholic Univ. of America Biol. Ser. 

 13, p. 8, 1933. Published by permission of the Catholic University of America.) 



Among the fungi investigated for fat synthesis are Endomyces vernalis, 

 Oidium lactis, Tonda utilis, Rhodotorula ghdinis, and species of Aspergil- 

 lus, Penicillium, Mucor, and Fusarium. From a practical standpoint, 

 only fungi which are capable of synthesizing fat in submerged culture 

 are of potential value. E. vernalis and 0. lactis do not produce fat effici- 

 ently in submerged culture. The fat content of various filamentous fungi 

 was determined by Preuss et al. (1934) and Ward et al. (1935). The use 

 of E. vernalis for fat and protein synthesis has been reviewed by Raaf 

 (1941). Starkey (1946) studied fat production by an unidentified soil 

 yeast, which under favorable conditions contained from 50 to 63 per cent 



