Abstract
The improvements of culture media were undertaken for higher vitamin B_<12> production. After some preliminary experiments the medium proposed by Hall of NRRL was adopted as the basic type and some modifications were made on it. No nitrogen sources more potent than SVP were found. Maltose and lactose were found to be the most potent carbon sources when applied singly, and the combination of glucose and lactose gave the highest result. The elongation of fermentation period and increased vitamin B_<12> production were observed with the addition of lactose. The best medium obtained was No. 47 on which the yield of the vitamin higher than 7.0μg/ml were obtained.
