Comparative analysis of microbial communities and volatile profiles in traditional Korean soybean paste (Doenjang)

Abstract

Doenjang, a traditional Korean fermented soybean paste valued for its functional properties, has an impact of regional meju origin on its microbial and metabolic profiles that remains poorly defined. In this study, doenjang samples prepared from meju sourced across six administrative regions of South Korea-Gangwon (GW), Gyeonggi (GG), Gyeongbuk (GB), Gyeongnam (GN), Jeonbuk (JB), and Jeonnam (JN)-were systematically evaluated using high-throughput metagenomic next-generation sequencing (155,337–219,330 reads per sample; Shannon diversity curves reaching clear saturation beyond 150,000 reads), integrated with volatile metabolite profiling. Taxonomic analysis revealed a fundamental ecological bifurcation among regions: the GW, GN, and JN groups formed a streamlined bacterial community dominated by Bacillus (>50% relative abundance), whereas the JB and GB groups exhibited markedly higher diversity enriched with lactic acid bacteria (LAB), with discriminant analysis further identifying region-specific biomarker taxa, including Tetragenococcus in JN, thermophilic Saccharopolyspora in GG, and Pediococcus in JB. Critically, integrating these bacterial profiles with volatile metabolite data uncovered precise mechanistic linkages between community composition and flavor chemistry: LAB abundance was strongly correlated with acetic acid and phenylethyl alcohol, driving sour and floral notes; Bacillus dominance was tied to dimethyl trisulfide, conferring savory aromas; and actinomycete abundance drove trimethylpyrazine synthesis, contributing nutty flavors. Collectively, these findings indicate that Korean doenjang harbors regionally distinctive microbial and volatile metabolite signatures, providing a precise genomic and biochemical foundation for the standardization and quality control of this functional food.