Vitamin B2 production by Acetobacterium sp. and its tetrachloromethane-resistant mutants

A strictly anaerobic, homoacetogenic bacterium strain 69, which produces high amounts of intracellular vitamin B₁₂, was isolated from sea sediment. Taxonomical and physiological studies revealed that the isolate should be classified in the genus Acetobacterium. The isolate grown on methanol produced ca. 11 mg of cyanocobalamin per gram dry cells after 7-d cultivation. Tetrachloromethane (TCM) resistant mutants, strain 67-7 and 69-23, were obtained from the isolate by ethylmethanesulfonate treatment, and produced ca. 23 mg of cyanocobalamin per gram dry cells for strain 69-7 and 20 mg for strain 69-23 in the presence of 10 μM of TCM.