NUTRITIONAL STUDIES INVOLVING VITAMIN B6 OF LACTIC ACID BACTERIA: I. THE EFFECTS OF VITAMIN B6 AND ALANINE ON THE GROWTH OF LACTIC ACID BACTERIA IN ALANINE-FREE SYNTHETIC MEDIA CONTAINING ESSENTIAL VITAMINS

Growth of Lactobacillus arabinosus, Lactobacillus casei, Streptococcus faecalis, and Leuconostoc mesentèroides were investigated in alanine-free synthetic media containing essential vitamins. These four lactobacilli required vitamin B6 for their growth. So the growth-promoting effects of pyridoxal, pyridoxamine, and pyridoxine were compared. In the absence of vitamin B6, alanine had varying effects on the growth. Any form of alanine had no effect on L. casei and a little on L. arabinosus. DL-Alanine promoted the growth of S. faecalis sufficiently but either D- or L-alanine remained ineffective. On Leuc. mesenteroides, however, each form of alanine was moderately effective. On the other hand, D-alanine exhibited inhibitory effect on the growth of L. casei in the semisynthetic medium. From these experimental results, it can be said that for the study of anti-vitamin B6 activities of various compounds, alanine-free synthetic medium is preferable to the semisynthetic one.