RIBOFLAVIN PRODUCING STRAINS OF MICROORGANISMS, METHOD FOR SELECTING, AND METHOD FOR FERMENTATION

摘要

Strains of yeast of the species Candida flareri are disclosed which can produce 10 grams of riboflavin per liter in 6 days, and in particular, strains identified by ATCC Accession Nos. 20849 and 20850. Riboflavin yields of more than 20 grams per liter in 200 hours have been achieved. Strains of the present invention have increased sensitivity to iron inhibition of flavinogenesis and have enhanced riboflavin production per cell at increased iron concentrations in the fermentation medium. The invention also is directed toward a process for selecting improved microorganisms which are resistant to inhibition of growth by depleted medium. Such selected microorganisms are then tested for riboflavin overproduction. The present invention is also directed toward a selection process in which mutated microorganisms are cultured in the presence of tubercidin, a purine analog. Mutant strains resistant to tubercidin are then tested for riboflavin overproduction. The present invention also includes a process for producing riboflavin by culturing strains of riboflavin overproducing microorganisms in a fermentation medium. Increased riboflavin production can be obtained by elevated iron concentrations in the nutrient medium. The fermentation is conducted and after cell growth levels off, riboflavin is recovered from the fermentation medium.