Report on Vitamin B12, Microbiological Method

Variations in the Growth Response of Four Different Vitamin B12 Assay Microorganisms to the Same Tissue and Standard Preparations1

“…When this investigation was begun, no thorough comparison had been made of the four commonly used microbiological assay methods for the determination of vitamin B12 in crude material using portions of the same sample and standard preparations. Krieger had reported different growth responses with L. leichmannii, 0. malhamensis, and E. coli from collaborative assays of four different samples (17). Lichtenstein et al found in parallel assays of the same extracts of liver that 0. malhamensis gave slightly higher values than L. leichmannii (19).…”

“…In all instances when liver tissue was assayed, the greatest growth response was obtained with E. coli, and the response was many times greater than that of the three other microorganisms which compared quite closely with each other. Krieger reported unusually high values for E. coli, but this was with a crude B12 fermentation product (17). When kidney tissue was being assayed, all values were much higher; this was expected because in the rat more vitamin B12 is stored in the kidney than in the liver (28).…”

“…It has been reported that the bound form of vitamin B12 is more labile in liver than in kidney (22). Krieger stated that the sodium metabisulfite treatment of a sample was of value in the stabilization of the naturally occurring analogues of vitamin B12 (17). Others have recommended sulfite for protecting cobalamins, especially hydroxocobalamin (28).…”

Analytical Microbiology

“…Joslyn and Gailbraith (1950) noted the difference in per cent transmission between a filter photometer and a spectrophotometer at the same wavelength. The 1953 Association of Official Agricultural Chemists Collaborative Assay of vitamin B12 had definite limits for the allowable assay range in terms of per cent transmission for each instrument used (Krieger, 1954). This was further modified in the 1954 study (Krieger, 1955) by use of a dried cell weight technique for establishing limits.…”

“…The 1953 Association of Official Agricultural Chemists Collaborative Assay of vitamin B12 had definite limits for the allowable assay range in terms of per cent transmission for each instrument used (Krieger, 1954). This was further modified in the 1954 study (Krieger, 1955) by use of a dried cell weight technique for establishing limits. By this technique any instrument may be calibrated to determine the minimum turbidity range for a given tion assay.…”