Microbial Composition of Fermented Korean Soy Paste (Doenjang) Prepared by Adding Different Herbs during Fermentation

Abstract

The microbiota involved in Korean soy paste (doenjang) fermentation are the key factors determining its quality aspects. In this study, doenjang was prepared by adding three different herbs (Peppermint, Korean mint, and Coriander), and their effect on the microbiota composition was evaluated by 16S rRNA metagenomic analyses. The β-diversity statistics indicated clear distinctions in the doenjang microbiota after the addition of herbs. A microbial composition analysis revealed that Tetragenococcus was among the dominant genera in the four doenjang groups, with a relatively higher abundance in the Korean mint group. In the Peppermint and Korean mint doenjang groups, the levels of undesirable microbes, such as opportunistic pathogens belonging to the genera Sphingobacterium and Pantoea, were significantly reduced. Additionally, other desirable microbes that are known to exhibit beneficial properties and produce bioactive compounds, such as Saccharopolyspora and Buttiauxella, were present at significantly higher levels. Significant negative correlations between members of the Bacillaceae and Halomonadaceae, Lactobacillaceae and Tissierellaceae, and the Lacobacillaceae and Erwiniaceae families were observed, indicating possible antagonistic relationships. Taken together, our results demonstrated that the incorporation of herbs, particularly Peppermint and Korean mint, during doenjang fermentation resulted in significant shifts in the microbial composition and could be utilized for beneficial effect on its fermentation.