Novel insight into the formation mechanism of umami peptides based on microbial metabolism in Chouguiyu, a traditional Chinese fermented fish.

Umami peptides formed by microbial metabolism play an important role in the umami taste of Chouguiyu. In this study, 138 umami peptides and 6 kinds of proteases in two categories from 35 microbial genera were identified from Chouguiyu during the fermentation process by peptidomics and metagenomics analysis, respectively. The interaction network maps between the umami peptides and protease-producing microbial genera in each protease classification were constructed based on Pearson's correlation coefficient after a two-way orthogonal partial least squares (O2PLS) evaluation. The proteases classified in 34 clusters of orthologous groups (COG) from Vagococcus, Peptostreptococcus, Acinetobacter, Psychrobacter, and Enterococcus played a major role in the formation of umami peptides. The core umami peptides with the highest abundance and correlation were mainly derived from troponin and myosin in mandarin fish. The lactic acid bacteria contributed most to the hydrolysis preparation of these umami peptides. This study is beneficial to screen the proteases and related microbial strains to improve the umami taste of Chouguiyu.