324 RIBOFLAVIN 



ribulose-5-phosphoric acid, by enzymatic oxidation of 6-phosphogluconic 

 acid could be demonstrated.^^'' 



3. Microorganisms as Producers^^ 



Different natural sources have been used for the production of vitamin 

 B2 by fermenting microorganisms. Whey and other milk by-products have 

 been treated with lactose-fermenting yeasts, especially Saccharomyces 

 fragilis, or with Clostridium bufylicum, several species of Lactobacilli, or 

 molds. Molasses or other carbohydrate mashes were fermented with vari- 

 ous strains of butanol-producing Clostridia, especially CI. acetohutylicum; 

 among the bacteria, this microorganism is one of the best producers of ribo- 

 flavin. Riboflavin is formed by numerous strains of Mycobacterium tubercu- 

 losis. In Mycobacterium smegmatis up to 3.6 mg. of riboflavin is formed per 

 100 mg. of the dried cells.^^'' 



A majority of the varieties of the yeast species Candida produce substan- 

 tial amounts of riboflavin when glucose is used as the carbon source. 

 Candida guilliermondia and Candida flareri were found to produce high 

 yields of riboflavin on a simple synthetic medium of low cost.^^ The use of 

 the Candida germs for commercial exploitation is very difficult because of 

 their extremely low tolerance for iron. 2 , 2'-Dipyridyl has been recom- 

 mended to control the iron content in fermentation media^^'' 



In 1935 GuiUiermond, a French mycologist, observed that Eremothecium 

 ashbyii in laboratory cultivation produced a yellow pigment which formed 

 crystals in the thread-like cells. The microorganism originally was isolated 

 as a pathogen for cotton plants in the Belgian Congo. The pigment has 

 since been identified as riboflavin. High yields of this vitamin have been 

 observed in fermentations with E. ashbyii, using sugar and nitrogenous 

 compounds in a deep fermentation method, with formation of up to nearly 

 500 mg. per liter of medium.^^ 



Ashbya gossypii also was found to be of value in the microbiological 

 production of riboflavin.^^ In shake cultures on a medium containing 4 % 

 glucose, 0.5 % peptone, and 2.5 % corn steep liquor solids, titers of 1000 

 mg. per liter were obtained. A large variety of factors influencing biosyn- 

 thesis of riboflavin in submerged aerobic cultivation by A. gossypii has 

 been studied. ^^ 



84* B. L. Horecker, P. Z. Smyrniotis, and J. E. Seegmiller, /. Biol. Chem. 193, 383 



(1951). 

 8^ For more details and references, see F. A. Robinson, footnote 1, pp. 148-154, and 



J. M. Van Lanen and F. W. Tanner, Jr., Vitamins and Hormone.'^ 6, 163 (1948). 

 86a R, L. Mayer and M. Rodbart, Arch. Biochem. 11, 49 (1946). 

 86 H. Levine e< al., Ind. Eruj. Chem. 42, 1176 (1950). 



86a R. Hickey, U. S. Pat. 2,425,280 (Aug. 5, 1947) [C.A. 41, 6668 (1947)]. 

 8' J. Wickerham, M. H. Flickinger, and R. M. Johnston, Arch. Biochem. 9, 95 (1946). 

 88 F. W. Tanner, Jr., C. Vojnovich, and J. M. Van Lanen, /. Bacteriol. 58, 737 (1949). 



