Microbial Community Variations and Bioconversion Improvements during Soybean-Based Fermentation by Kefir Grains

Abstract

Soybeans possess unexpected flavors and are difficult to be absorbed by the gastrointestinal tract. Kefir grain fermentation provides diverse strains and bioactive compounds, which may enhance flavor and bioaccessibility. Third-generation sequencing was applied to analyze the microbial diversity in milk and soybean kefir grains in this study. In both types of kefir grains, the most common bacterial genus was Lactobacillus, and their fungal communities were dominated by Kazachstania. Lactobacillus kefiranofaciens was the most abundant species in kefir grains, while Lactobacillus kefiri showed a higher proportion in soybean kefir grains. In addition, the quantification of free amino acids and volatile flavor compounds in soybean solution and soybean kefir have shown the increased content of glutamic acid and a decreased amount of unpleasant beany flavor compounds, demonstrating that the nutritive value and sensory properties of soybean can be improved by kefir grain fermentation. Finally, the bioconversion of isoflavones during fermentation and in vitro digestion was evaluated, suggesting that fermentation is beneficial for aglycone formation and absorption. To conclude, kefir fermentation is proposed to change the microbial structure of kefir grains, promote the nutritional value of soybean-based fermented products, and provide possible solutions for the development of soybean products.

Development and Evaluation of Bioconverted Milk with Antimicrobial effect against Oral Pathogens and α-Glucosidase Inhibitory Activity

“…Furthermore, various new quality-related components such as phenolic acids, flavones and their glycosides, alkaloids, and terpenoids have been identified due to changes in chemical composition during microbial bioconversion with plants in recent years [12]. Microbial bioconversion showed a synergistic effect compared to simple application of lactic acid bacteria (LAB), such as increasing the fermentation ability due to soybean protein and enhancing the inflammatory bowel disease-alleviating effect by boosting the bioactivity of anthocyanin [13,14].…”