Analysis of D-amino acid in Japanese post-fermented tea, Ishizuchi-kurocha.

The D-amino acid content of Ishizuchi-kurocha, a post-fermented tea produced in Ehime, Japan, was measured. Ishizuchi-kurocha mainly contains D-glutamic acid and D-alanine, but it also contains a small amount of D-aspartic acid. Two types of lactic acid bacteria, and , are the main species involved in lactic acid fermentation during the tea fermentation process. Therefore, the D-amino acid-producing abilities of strains of these two species isolated from Ishizuchi-kurocha were examined. Specifically, the production of D-aspartic acid, D-alanine, and D-glutamic acid by and strains was observed. The amount of D-aspartic acid produced by was low. D-glutamine was detected in culture supernatant but not in bacterial cells. D-arginine was detected in bacterial cells of the strains but not in the culture supernatant. Both the and strains possessed at least three kinds of putative racemase genes: alanine racemase, glutamate racemase, and aspartate racemase. However, their expression and enzyme activity remain unknown. and could play an important role in the production of D-amino acids in Ishizuchi-kurocha. In fact, Ishizuchi-kurocha is expected to possess the effective physiological activities of D-amino acids.