Abstract
Propionibacterium shermanii was cultured for 9 days at 30℃ in the medium to which cyanocobalamin or hydroxocobalamin was added from the beginning of the cultivation or on the 2nd, 4th, 6th or 8th day in the incubation period, respectively. Total amount of vitamin B_<12>-group compounds was assayed spectrophotometrically after conversion to dicyanocobalamin, and their forms were studied by paper ionophoresis and absorption spectrophotometry after fractionation with CM-cellulose. In the case of hydroxocobalamin the greater part of the amount exogenously added on the 8th day was incorporated into the cell and transformed to DBCC as well as from the beginning of the incubation. In the case of cyanocobalamin the vitamin B_<12>-active substances in the cell consisted of cyanocobalamin and DBCC. The amounts were lowered as the time of the addition was delayed. Hydroxocobalamin was not detected in the cell cultivated with cyanocobalamin. From the results it would seem appropriate to conclude that the affinity to the bacterial cell and the rate of conversion to DBCC of cyanocobalamin were smaller than those of hydroxocobalamin.
