Exploring the capacity of Bacillus species for production of kokumi γ-glutamyl peptides: A comparative study

γ-Glutamyl peptides are an important class of kokumi compounds that enhance the palatability of food. To investigate the ability of Bacillus species to produce γ-glutamyl peptides, strains of B. subtilis, B. safensis, B. velezensis, B. altitudinis and B. paralicheniformis, were isolated from the fermented seed condiment “Kantong” and cultured in the dark in a conventional medium for 5 days. Quantitation of γ-glutamyl peptides was performed alongside analyses of bacterial growth and γ-glutamyltransferase (GGT) activity. Results showed that all strains could produce a variety of γ-glutamyl peptides. Compared to the other strains, strains of B. subtilis and B. safensis demonstrated greater capacities to generate target γ-glutamyl peptides, achieving maximum concentrations of 2.02 and 1.77 mg/L, respectively. Moreover, no direct correlation between GGT activity and γ-glutamyl peptide concentrations was observed during fermentation, and these two indicators were reported for the first time for B. safensis and B. paralicheniformis. This study provides valuable insights into the generation of γ-glutamyl peptides through Bacillus fermentation, facilitating the development of cost-effective and environmentally friendly approaches for producing kokumi seasonings.