Effects of Bacillus amyloliquefaciens fermentation on phytochemical, flavor characteristics, antithrombotic, and prebiotic activities of soybean/radish mixed substrate.

Soybeans and radishes are among the most widely consumed vegetables, rich in high-quality proteins and soluble functional polysaccharides with significant nutritional complementarity. However, the low bioavailability, nutritional value, flavors and health benefits have largely restricted their high-value utilization. In the present study, the soybean/radish mixed-substrate was initially established to investigate the alterations of their phytochemical, flavor characteristics, and biological activities during fermentation. Firstly, several Bacillus strains were screened for fibrinolytic activity based on soybean/radish mixed-substrate using casein agar and fibrin plates. As a result, Bacillus amyloliquefaciens indicated a high fibrinolytic activity of 8279.91 U/mL at the optimum fermentation conditions (24 h, 35 °C, and 5% soybean powder). B. amyloliquefaciens significantly modulates the content of total protein, sugar, phenol, and increases antioxidant activity, along with an improved flavors including 2,5-dimethylpyrazine, acetoin, phenethyl alcohol, and 2-octanone. To evaluate the health benefits of fermented products of B. amyloliquefaciens, κ-carrageenan induced mouse tail thrombus model was employed. B. amyloliquefaciens and/or Lactiplantibacillus plantarum fermentation significantly decreased relative length of tail necrosis, accompanied by alleviated histopathological damage, reduced levels of thromboxane B2, hyperlipidemia, and pro-inflammatory cytokines. 16S rRNA sequencing of gut microbiota showed fermentation products of B. amyloliquefaciens and/or L. plantarum enhanced relative abundance of Bifidobacteriaceae, Muribaculaceae, and decreased that of Desulfovibrionaceae. A total of 26 metabolism-related differentially expressed KEGG Orthology genes were identified, involving biosynthesis of secondary metabolites and cofactors, indicating underlying metabolism-regulatory capacity. Collectively, this study exploits the potential of the soybean/radish mixed-substrate as the next generation of fermented foods, improving quality, flavor, nutrition, and health values.