Effects of Soybean Oligosaccharides Extracted from Defatted Soybean Meal on Gut Microbiota and Metabolites during in Vitro Fermentation Process

To investigate the in vitro digestion and fermentation properties of soybean oligosaccharides (SBOS) extracted from defatted soybean meal, the changes in monosaccharide composition and molecular mass were analyzed. Subsequently, the effect of SBOS on microbial community structure and metabolites was studied by 16S rRNA gene sequencing and untargeted metabolomics based on liquid chromatography-mass spectrometry. Results showed that SBOS was not easily enzymolyzed during simulated digestion and could reach the large intestine through the digestive system. The significant decrease in the molecular mass of SBOS after in vitro fermentation indicated its utilization by the gut microbiota, which increased the contents of short-chain fatty acids and lactic acid, thereby reducing the pH of the fermentation broth. Moreover, the core community was found to consist of Blautia, Lactobacillaceae, and Pediococcus. SBOS up-regulated beneficial differential metabolites such as myo-inositol, lactose, and glucose, which were closely related to galactose, amino sugar, and nucleotide sugar metabolism. This study will provide a reference for exploring the relationship between the gut microbiota and the metabolites of SBOS, and provide a basis for the development and application of SBOS as an ingredient for functional products.