抄録
B group vitamin requirements and production were examined in axenic cultures of several freshwater phytoplankters which were isolated from the water of a eutrophic lake, Lake Kojima.
All the phytoplankters used, Scenedesmus sp., S. abundance, Chlorella sp. (A), Chlorella sp. (B), Chlamydomonas sp., Caraeria sp., and Chroococcus sp., were found to have no vitamin requirements and to produce considerable amounts of vitamin B12, thiamine, and biotin in the culture media as the age of the culture increased.
The vitamins produced as well as the production rate of the vitamins varied with both the species of the phytoplankters and the stages of the growth. Generally the B group vitamins were secreted increasingly with the cell multiplication. The amounts of the B group vitamins produced per ml of medium per day during the early logarithmic phase of growth were generally more abundant than those during the stationary phase. On the other hand, the amounts of vitamins produced per cell per day did not vary regularly with the different stages of the growth. These values were mostly 10-8-10-7 pg/cell/day for vitamin B12, 10-6-10-5 pg/cell/day for thiamine, and 10-5-10-4 pg/cell/day for biotin.
From the present results, it is suggested that some species of the phytoplankters may significantly contribute to the production of the dissolved B group vitamins found abundantly in the waters of the lake.
