Abstract
A modified microbiological assay (microplate assay) of cyanocobalamin (B_<12>) was studied by using a 96-well microplate. Under anaerobic conditions, the growth response of Lactobacillus leichmannii ATCC 7830 to B_<12> in the microplate was similar to that in the tube. The correlation coefficient between B_<12> values・obtained by the microplate assay and those obtained by the tube assay was 0.997. B_<12> autoclaved in the assay medium was converted to a substance which was different from the on-treated B_<12> by HPLC. In the microplate assay, the products of B_<12> autoclaved in the assay medium and treated by sodium bisulfite were biologically more active than non-treated B_<12> on the growth of L. leichmannii. When the microplate assay was used for B_<12> compounds altered by those treatments, standard B_<12> should be used in the sample procedure.
