Analyses of microbial community of naturally homemade soybean pastes in Liaoning Province of China by Illumina Miseq Sequencing

Traditional Chinese soybean pastes are homemade using natural fermentation and are quite common and popular in Liaoning Province. In this study, we investigated microbial diversity by collecting 23 samples from 10 cities and sequenced them using 2 x 300 bp Illumina Miseq Sequencing. 16S and ITS primers were used to amplify the V3-V4 region of the bacterial 16S rRNA gene and the ITS1 region of the fungal ITS rDNA gene, respectively. In total, 687,888 filtered bacterial sequences were obtained from nineteen samples and 1,091,649 filtered fungal sequences were obtained from twenty samples. Among the bacterial sequences, Firmicutes (74.77%), Proteobacteria (22.61%), and Actinobacteria (2.55%) were the predominant phyla, with Staphylococcus making up most of the Firmicutes. Among the fungal sequences, Ascomycota, Basidiomycota and Zygomycota accounted for 94.88%, 3.29% and 1.77%, respectively, while Glomeromycota and Chytridiomycota accounted for the remaining 0.06%. Most of the species from Ascomycota were unclassified Trichocomaceae and Debaryomyces, including 404578 and 187827 sequences, respectively. The microbial community in each sample was unique, most likely due to the geographical differences and external factors including the environment and manufacturing process during the fermentation. Soybean paste is the result of fermentation involving a great diversity of microorganisms, which include not only bacteria but also fungi.