[Flavin pool in Propionibacterium shermanii and the formation of corrinoids by bacterial cultures].

The content of flavins and vitamin B12 was studied in the cultures of Propionibacterium shermanii. The limited ability of propionic bacteria to synthesize 5,6-dimethylbenzimidazole, the nucleotide base in the true forms of vitamin B12, was found to be caused by a deficiency of the biogenetic precursor (riboflavin). Exogenous 5,6-dimethylbenzimidazole had no effect on the processes of flavinogenesis. In the absence of the nucleotide base, the yield of the true forms of vitamin B12 increased upon aeration of cultures which were grown for four days on an iron-deficient medium in the anaerobic conditions.