Vitamin B_<12> content of 11 samples of mash of "Takuan-zuke" and 20 samples of "Nukamiso" (fermented paste of rice bran) was determined by Euglena gracilis var. bacillaris. The vitamin B_<12> content of the former was from 32 to 182 mμg per 100 g, and the mean value was 74 mμg per 100 g. The vitamin B_<12> content of the latter varied from 30 to 5040 mμg per 100 g, and the mean value was 700 mμg per 100 g. From vitamin B_<12>-rich "Nukamiso" various strains of yeast, acid forming bacteria and aerobic bacteria were isolated, and their vitamin B_<12> producing ability was examined. It was confirmed that yeasts had slightly vitamin B_<12> producing ability, as 12-28 mμg/dl of broth, however some strains of aerobic bacteria proved to have a strong vitamin B_<12> producing ability, its maximum value being 5.2 μg/dl of broth. On the contrary, lactic bacteria and other acid forming bacteria had no vitamin B_<12> producing ability but rather seemed to consume vitamin B_<12>.