Isolation and Identification of Tetragenococcus halophilus Strains from Traditional Fermented Soybean Paste and Screening for Their Umami-Enhancing Activity

This study was implemented in order to obtain Tetraplococcus halophilus with the ability to produce umami peptides. A total of 83 strains suspected of being T. halophilus were isolated from 96 naturally fermented soybean paste samples from seven different areas of Liaoning province. Through DNA extraction, 16S rDNA sequencing and comparative homology analysis, 47 of these strains were identified as T. halophilus and were screened for their ability to produce polypeptide, γ-glutamyl transpeptidase and protease and their electronic tongue flavor values. Moreover, factor analysis and factor score comprehensive evaluation were carried out, revealing that T. halophilus LY9-1 had the greatest potential to produce umami peptides. The results of electronic tongue also proved that the fermentation broth of T. halophilus LY9-1 had the highest umami value of 15.05 ± 0.02, as well as protease activity of (85.45 ± 0.03) U/mL, γ-glutamyl transpeptidase activity of (44.23 ± 0.03) U/mL, and polypeptide production of (17.55 ± 0.13) mg/mL. It is speculated that the strain has a strong umami-enhancing potential. The findings reported here can motivate further research on the umami-enhancing mechanism and encourage the industrial application of T. halophilus LY9-1 to enhance the umami of fermented foods.