Abstract
Summary
A microbiological assay for vitamin B12 using Lactobacillus leichmannii (ATCC 4797) has been developed. The assay medium contains crystalline amino acids as the nitrogen source and adsorbed tomato juice filtrate as a source of unidentified growth factors. A high level of cysteine and ferrous sulfate are present in the medium to keep it in the necessary reduced state. Data are given to show the degree of precision and reproducibility to be expected from the assay.
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