Physicochemical properties, structure and regulatory effect on gut microbiota of dietary fiber extracted from soybean meal via dry fractionation

Currently, dry fractionation is employed to extract dietary fiber (DF) from food processing bypuroduct owing to its advantages of low energy and eco-friendly. Procedures of dry fractionation mainly include milling and air classification. Soybean meal (SBM) is a processing byproduct rich in DF. Few studies have used dry fractionation to extract SBM dietary fiber (SMF), and the physicochemical properties, structural characteristics, and activity of SMF extracted via dry fractionation remain unclear. Herein, SMF was prepared via dry fractionation and results showed that compared with that of SBM without pores and high crystallinity, SMF had loose and porous surface and low crystallinity. Moreover, the water holding capacity, oil holding capacity and swelling ability of SMF were significantly higher than SBM. After 24 h of in vitro fecal fermentation, the SMF group produced abundant short chain fatty acids (SCFA) such as acetic, propionic, and butyric acids and the total SCFA production was substantially higher than that in the inulin (INL) group. SMF also promoted the relative abundance of beneficial bacteria such as Prevotella, Dialister, and Bifidobacterium and reduced the relative abundance of harmful bacteria such as Escherichia–Shigella. In conclusion, SMF extracted via dry fractionation can significantly alter the relative abundance and diversity of gut microbiota and promote the production of SCFA, which is conducive to the regulation of the human gut microbiota. This study can provide insights into the preparation of DF via dry fractionation and provide theoretical basis for SMF to be used as a prebiotic.