In Vitro Fermentability of Soybean Oligosaccharides from Wastewater of Tofu Production

Soybean oligosaccharides (SBOS) isolated from wastewater of tofu production were studied in terms of their structural characteristics and in vitro fermentation by human fecal inocula. Three sub-fractions named Z1 (14%), Z2 (13%), and Z3 (17%) were obtained by Sephadex G-15 column separation. Z1 contained mainly stachyose; Z2 and Z3 contained stachyose, raffinose, and sucrose with different relative percentages. The in vitro batch fermentation model of human intestinal bacteria including 0, 12, 24, and 48 h was used to investigate the fermentation characteristics of SBOS. According to the results, during the fermentation process, the molecular weight of oligosaccharides decreased significantly with increasing fermentation time, indicating that oligosaccharides could be utilized and degraded by the colonic microbiota. Furthermore, SBOS could significantly promote the production of short-chain fatty acids (SCFAs), especially acetic, propionic, and butyric acids. SBOS increased the abundance of Firmicutes, while that of Proteobacteria was decreased. Additionally, SBOS could promote the proliferation of Dialister, Bacteroides, and Akkermansia at the genus level. Therefore, SBOS can be potentially used as prebiotic promoting gut health.