Next-Generation Sequencing Analyses of Bacterial Community Structures in Soybean Pastes Produced in Northeast China

Fermented soybean foods contain nutritional components including easily digestible peptides, cholesterol-free oils, minerals, and vitamins. Various fermented soybean foods have been developed and are consumed as flavoring condiments in Asian regions. While the quality of fermented soybean foods is largely affected by microorganisms that participate in the fermentation process, our knowledge about the microorganisms in soybean pastes manufactured in Northeast China is limited. The current study used a culture-independent barcoded pyrosequencing method targeting hypervariable V1/V2 regions of the 16S rRNA gene to evaluate Korean doenjang and soybean pastes prepared by the Hun Chinese (SPHC) and Korean minority (SPKM) populations in Northeast China. In total, 63399 high-quality sequences were derived from 16 soybean paste samples collected in Northeast China. Each bacterial species-level taxon of SPHC, SPKM, and Korean doenjang was clustered separately. Each paste contained representative bacterial species that could be distinguished from each other: Bacillus subtilis in SPKM, Tetragenococcus halophilus in SPHC, and Enterococcus durans in Korean doenjang. This is the 1st massive sequencing-based study analyzing microbial communities in soybean pastes manufactured in Northeast China, compared to Korean doenjang. Our results clearly showed that each soybean paste contained unique microbial communities that varied depending on the manufacturing process and location.