Determination of Vitamin B 12 in Human Serum by a Mutant of Escherichia coli

Abstract

Summary

The vit. B₁₂ assay using a mutant strain of E. coli was modified by addition of methionine-free casein hydrolysate to a mineral medium. This method gave better growth and allowed a more accurate estimation of the vit. B₁₂ than previous methods using the same organism. The assay required only 40-48 hr as compared with 7-9 days when E. gracilis is used; the set-up, too, is very simple. The test proved satisfactory for the determination of vit. B₁₂ in human serum. The vit. B₁₂ content of sera of healthy subjects determined by this method ranged from 200 to 1000 μμg/ml, while sera of patients suffering from pernicious anemia contained only 50-130 μμg/ml.