Genetic Background Behind the Amino Acid Profiles of Fermented Soybeans Produced by Four spp.

Strains of four spp. were respectively inoculated into sterilized soybeans and the free amino acid profiles of the resulting cultures were analyzed to discern their metabolic traits. After 30 days of culture, showed the highest production of serine, threonine, and glutamic acid; exhibited the highest production of alanine, asparagine, glycine, leucine, proline, tryptophan, and lysine. increased the γ-aminobutyric acid (GABA) concentration to >200% of that in the control samples. produced a somewhat similar amino acid profile with . Comparative genomic analysis of the four strains and the genetic profiles of the produced free amino acids revealed that genes involved in glutamate and arginine metabolism were not common to the four strains. The genes (encoding a glutamate decarboxylase), (amino acid permease), and (γ-glutamyl-γ-aminobutyrate hydrolase) determined GABA production, and their presence was species-specific. Taken together, and were respectively shown to have high potential to increase concentrations of glutamic acid and GABA, while has the ability to increase essential amino acid concentrations in fermented soybean foods.