Insoluble dietary fiber from soy hulls regulates the gut microbiota in vitro and increases the abundance of bifidobacteriales and lactobacillales

We evaluated soy hull dietary fibers (SHDF) extracted from different raw materials, in terms of their chemical composition, physicochemical properties, structure, and ability to regulate fecal microflora, in order to investigate the properties and functions of SHDF. The structures of insoluble dietary fiber from soy hull with oxalic acid extraction (IDFO) and insoluble dietary fiber from soy hull with citric acid extraction (IDFC) were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Compared with IDFO, IDFC had larger crystalline regions, and a higher water retention capacity (4.92 g/g), water swelling capacity (4.77 mL/g), oil adsorption capacity (1.60%), alpha-amylase activity inhibition ratio (12.72%), glucose adsorption capacity (1.59-13.42%), and bile acid retardation index (5.18-26.61%). Given that the gut microbiota plays a pivotal role in health homeostasis, we performed a detailed investigation of the effects of dietary fiber on fecal microbiota through 16S rDNA high-throughput sequencing. As revealed by Venn, principal component analysis, and 3D-principal co-ordinates analysis analysis, the structure of the fecal microbiota community was markedly altered by intake of IDFO and IDFC. In particular, the abundance of Bifidobacteriales and Lactobacillales significantly increased to varying degrees as a result of IDFO and IDFC intake. Altogether, this study demonstrates a prebiotic effect of SHDF on the fecal microbiota in vitro and provides a basis for the development of SHDF as a novel gut microbiota modulator for health promotion.