Abstract
In previous paper, we could readily isolate a substance, designated as X-factor, from bacterial cell products for feed supplement use and provided some evidence suggesting that the substance was cobinamide or its closely related compound. The present work was undertaken to ascertain whether X-factor is available as precursor in biosynthesis of cobamides with Propionibacterium shermanii. For this purpose, the organism was cultivated for 5 days at 30℃ in media containing various amounts of X-factor and 5,6-dimethylbenzimidazole (DBI) and the cobamides contents of cells and supernatant were determined by microbiological assay. For example, the cells containing about 2.2μg of cobamides per ml of medium were obtained when 3.0μg of X-factor and 2.0μg of DBI were added per ml of medium. While, in the supernatant, less amounts of cobamides were found. The addition of much amounts of X-factor caused a striking increase in the yield of cobamides in the cells. On the contrary, only 0.2μg of cobamides were found to be produced without added precursors.
