Microbial community analysis of viable cells and genomes in kyejang, a traditional Korean fermented beverage

The relationship between diet and gut microbial community is widely studied, and foods that might be sources of beneficial microorganisms have garnered interest. Here, we analyzed the changes in the microbial community of kyejang, a traditional Korean fermented beverage, made with nuruk, cinnamon, and medicinal herbs fermented at 10, 20, and 30 degrees C for 7 days. Using selective media, the decrease in the numbers of Bacillus pumilus, B. amyloliquefaciens, and B. subtilis colony-forming units was observed from the initial fermentation stage to day 7, whereas those of Leuconostoc mesenteroides and Lactobacillus curvatus increased during this period. Next-generation sequencing revealed 719 operational taxonomic units (OTUs) at the onset of fermentation of kyejang (control), confirming the presence of diverse microorganisms. Leuconostoc spp. was dominant for 7 days at 10 degrees C and 20 degrees C, whereas Lactobacillus spp. was dominant for 7 days at 30 degrees C. Therefore, the microbial community of fermented kyejang was dominated by lactic acid bacteria; however, the number of OTUs decreased to 43 within 7 days of fermentation at 30 degrees C, indicating that the microbial community simplified as fermentation proceeded. Based on these results, kyejang is expected to contribute to the diversity of gut lactic acid bacteria and traditional beverages.