Abstract
Summary
Substitution of L-, DL- and D-valic acids in place of valine in the nutrition of 10 lactic acid bacteria has been investigated. Five of the bacteria were able to utilize either optical form of valic acid efficiently in place of L-valine, even though the requirement for this amino acid is highly L-specific. Three of the latter 5 bacteria, on the other hand, could be made to exhibit a marked preference for D-valic acid by selective antagonism of L-valic acid with the inhibitor, DL-a-hydroxybutyric acid. One other organism showed a similar preference for D-valic acid without use of the inhibitor, but in this case utilization of D-valic acid was relatively inefficient. The a-hydroxy acid-dependent organism, L. casei 280-16A, was D-specific in its utilization of valic acid as an a-hydroxy acid source, but was not optically specific in its utilization of valic acid as a valine substitute.
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