STUDIES ON THE PRODUCTION OF VITAMIN B12-ACTIVE SUBSTANCES BY MICROORGANISMS

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Abstract
Vitamin B12activity, as determined by the Lactobacillus lactis Dorner agar plate assay, was shown by 64.6% of 537 bacteria isolated from soils, seed, manure, and poultry house litter, and by 66.6% of 676 actinomycetes from soils. For the primary isolation of active forms a simple medium without growth factors was superior to more complex media; however, the latter were more suitable for vitamin production. Further work, in which the Lactobacillus leichmannii assay method was used, indicated that highest yields were given by species of Nocardia isolated from soil, the B12-active substance being chiefly associated with the cells. Vitamin B12values could be increased by improving the method of extraction. Survivors of ultraviolet irradiation lethal to the great majority of treated cells were not significantly different in B12producing capacity with respect to mean or dispersion when compared with nonirradiated strains.