METABOLIC PRODUCTS 273 



Eremothecium ashbyi was shown to produce as much as 157 mg. per 

 liter of riboflavin when cultivated on glucose-peptone medium (Renaud 

 andLachaux, 1945). Aeration was necessary. Foster (1947) has recom- 

 mended a molasses medium for the commercial production of riboflavin 

 by E. ashbyi. The closely related species, Ashbya gossypii, also synthe- 

 sizes riboflavin in large amounts (Tanner et al., 1949). 



Peltier and Borchers (1947) determined the amount of riboflavin 

 produced by 240 isolates of soil fungi when grown on wheat bran. Forty- 

 five isolates produced 2 mg. or more of riboflavin per 100 g. of dry mold 

 bran. An unidentified species of Aspergillus produced 5.8 mg. of ribo- 

 flavin per 100 g. of substrate. Species of Fusarium and Aspergillus were 

 outstanding producers of riboflavin. 



The commercial microbiological synthesis of riboflavin depends upon 

 the use of either E. ashbyi or C. acetobutyliciim (Tanner et al., 1949). 



Vitamin B12 was isolated in crystalline form from liver and shown to 

 contain cobalt (Rickes et al., 1948; Smith, 1948). It is the only vitamin 

 so far discovered which contains a metal as an integral part of the mole- 

 cule. Streptomyces griseus and other microorganisms synthesize this 

 vitamin. Sheep and cattle pastured on cobalt-deficient soils (Florida, 

 Australia, New Zealand) develop a deficiency disease. Ingested cobalt 

 is more effective than injected cobalt in overcoming this condition. It 

 may be assumed that cobalt is used in the synthesis of vitamin B12 by the 

 action of the microorganisms of the rumen and intestine. Vitamin B12 

 appears to be the anti-pernicious-anemia factor (West, 1948). Whether 

 it is the animal protein factor is undecided. The cow-manure factor may 

 be vitamin B12 (Lillie et al., 1948). 



Until the structure of vitamin B12 is determined and methods of syn- 

 thesis developed, certain natural products will remain the only source 

 of this vitamin. The only organic moiety of vitamin B12 so far disclosed 

 is l-a-D-ribofuranosido-5,6-dimethylbenzimidazole (Brink et al., 1950). 

 Vitamin B12 is obtained as a by-product from various industrial processes, 

 especially streptomycin production. It is evident that the medium must 

 contain cobalt; within limits, the amount of vitamin B12 synthesized by 

 Streptomyces griseus is a function of the cobalt content of the medium. 

 Maximum synthesis was observed when the medium contained 1 to 2 mg. 

 of cobalt per liter (Hendlin and Ruger, 1950). 



None of the other vitamins appears to be synthesized by fungi in 

 amounts which would make the latter attractive sources for the isolation 

 of pure vitamins. The value of these vitamins in fungi used for food was 

 discussed previously. Yeast can be fortified with thiamine so that it 

 may serve as a therapeutic agent. By adding synthetic thiamine to an 

 aerated yeast culture, yeast was produced which contained 6 mg. of 

 thiamine per g. (Van Lanen et al., 1942). 



