THE MICROBIOLOGICAL ASSAY OF VITAMN B_<12> UTILIZING AUXOTROPHIC MUTANTS OF ESCHERICHIA COLI : (VI) COMPARATIVE STUDIES ON VITAMIN B_<12> TITER OF HUMAN BLOOD DETERMINED BY E.COLI MUTANT 215 AND Lactobacillus Leichmannii ATCC 4797

Abstract

The turbidimetric method of the author for the microbiological determination of vitamin B_<12> utilizing the E.coli mutant 215 gave results with 8 samples of human whole blood which were comparable to those obtained by K. Murata and T. Miyamoto of Osaka City University utilizing L. leichmannii method. Mean value of vitamin B_<12> activities of KCN treated blood was 0.297 ± 0.039 mμg/ml for E.coli mutant and 0.251±0.054mμg/ml for L.leichmannii. The value of papain treated blood was 0.323±0.035 mμg/ml for E.coli and 0.260±0.069 mμg/ml for L. leichmannii.