Determination of Vitamin B12 in Human Serum by a Mutant of Escherichia coli

Abstract

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