抄録
Investigations were made on the determination of cyanocobalamin present in natural materials together with a variety of the related factors by a static culture method with a protozoan, Ochromonas malhamensis.
1. The determination of vitamin B12 is possible by a static culture method using Ochromonas malhamensis, although the assay range is narrower as compared with a shaking culture.
2. Assay test tubes of small size with aluminium cups are more convenient for the assay by a static culture method.
3. The higher the inoculum amount, the shorter the length of the incubation time necessary for assay. It. might be most convenient to use 1:10 dilution of 5-day culture of the test organism, since the heavy inoculum causes a high blank, and gives vigorous growth during a shorter incubation.
4. The use of cyanide at the concentration of about 1μg per tube facilitates the extraction of vitamin B12 from natural materials.
5. For the purpose of widening the assay range in the dose-response curve of static culture, the effects of various kinds of surface-active agents were tested on the growth of the test organism. Especially effective agents could not be found except for Myri 52 with which approximately linear dose-response curve was obtained within the concentration of 0 to 0.2mμg of vitamin B12.
6. Satisfactory recoveries were obtained with the extracts of beef liver and methane fermentation products of night soil and distillers' wastes.
