Further Observations on the Microbiological Assay for Vitamin B 12 Using Lactobacillus leichmannii.

Abstract

Summary

1. A comparison was made of vit. B₁₂, B_12b, B_12c and “ammino-cobalamin” in the microbiological assay with Lactobacillus leichmannii using aseptic or non-aseptic assay technic. The growth response of L. leichmannii was significantly less when vit. B₁₂ was added aseptically to the medium as compared to when vit. B₁₂ was autoclaved in the medium. This effect was not noted for vit. B_12b, B_12c and “ammino-cobalamin.” 2. By means of paper strip chromatography it was demonstrated that when vit. B₁₂ is autoclaved with thiomalic acid, vit. B₁₂ is transformed into a new compound which is distinct from vit. B_12b. The vit. B₁₂-thiomalic acid reaction product is more potent microbiologically than vit. B₁₂ when the compounds are compared by aseptic assay technic. 3. The significance of these results in the interpretation of the microbiological assay of the vit. B₁₂ content of natural materials when vit. B₁₂