抄録
The method of microbiological assay of vitamin B_<12> using Ochromonas malhamensis which responds specifically to cyanocobalamin was investigated. The organisms were cultured in the aluminium-capped test tubes placed slantly in incubator for 90 hours at 29℃, and then the growth was determined. It was recognized that the available range of determination of vitamin B_<12> per tube was 0.02-0.2mμg. When more than 4 mg or 2 mg of salts was included in the tubes containing 0.05mμg or 0.2mμg of vitamin B_<12> per tube respectively, the growth of the organism was considerably inhibited. Less than 0.5mg of DL-methionine per tube was not effective to the growth of the organisms. Vitamin B_<12> values of animal foods found by this method were almost the same with the values by the method using L. leichmannii #4797. However, vitamin B_<12> values of weeds by the method with O. malhamensis were less than 80% of those by the method with L. leichmannii.
