D- and l-amino acid concentrations in culture broth of Lactobacillus are highly dependent on the phylogenetic group of Lactobacillus

Abstract

d-amino acids produced by Lactobacillus are thought to contribute to the taste quality and health functions; however, no studies have comprehensively evaluated the concentrations of the D- and L-forms of amino acids separately in individual Lactobacillus strains. To gain insight into amino acid concentrations in Lactobacillus, we evaluated amino acid concentrations in culture broth of Lactobacillus separately for the D- and L-forms. Lactobacillus strains were cultured in culture broth, and the amino acid concentrations in supernatant were assessed. The amino acid concentrations obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were subjected to cluster analysis based on Bray-Curtis distance with Ward's minimum variance method. In the analysis of amino acid concentrations under culture with different monosaccharides, the distances among strains cultured with the same monosaccharide were significantly greater than those among cultures of the same strain under different monosaccharides (p < 0.01). The cluster analysis of amino acid concentrations under culture with the same monosaccharide suggested that strains belonging to the same phylogenetic group of Lactobacillus exhibited similar concentrations of amino acids. Data analyses of 70 strains belonging to 17 Lactobacillus taxa indicated that the concentrations of amino acids were highly dependent on the phylogenetic group of Lactobacillus and that the group differences in amino acid concentration were strongly driven by differences in l-serine and d-alanine concentrations. Our results indicate that it is important to evaluate D- and l-amino acids separately when evaluating variations in amino acid concentrations. Because d-alanine has the potential to affect taste quality, the results of this study may provide insight into the taste quality of fermented food produced by Lactobacillus.