Influence of 5,6-dimethylbenzimidazole (DMB) on vitamin B12 biosynthesis by strains of Propionibacterium

Work on vitamin B₁₂ biosynthesis in whey permeate using 5,6-dimethylbenzimidazole (DMB) as a precursor has often been carried out, but with no reference to the stage of fermentation at which it is to be added to the fermentation medium. In the present paper we report 168 h incubation as the optimum time for vitamin B₁₂ biosynthesis and the effect of DMB addition at four phases of fermentation, on vitamin B₁₂ productivity, growth and substrate utilization by three strains of Propionibacterium. The infusion of DMB at the end of 144 h of incubation (24 h before the end of fermentation) has been found optimum for maximum metabolic efficiency of the cultures.