*Article* **Changes of High-Purity Insoluble Fiber from Soybean Dregs (Okara) after Being Fermented by Colonic Flora and Its Adsorption Capacity**

**Bo Lyu 1,2,†, Yi Wang 2,3,†, Xin Zhang 1,2, Yuxi Chen 2,3, Hongling Fu 2,3, Tong Liu 4, Jianyu Hao 5, Yang Li 1,2, Hansong Yu 2,3,\* and Lianzhou Jiang 1,2,\***


**Abstract:** In order to explore the changes and properties of high-purity insoluble dietary fiber from okara (HPIDF) after entering the colon and be fermented by colonic flora, fermented high-purity insoluble dietary fiber (F-HPIDF) was obtained by simulated fermentation in vitro by HPIDF and colonic flora from C57BL/6 mice. For exploring the differences of HPIDF and F-HPIDF, the changes of structure (SEM. FTIR, XRD, particle size, specific surface area, monosaccharide composition) and adsorption properties (water, oil, heavy metal irons, harmful substances) of HPIDF/F-HPIDF were explored. The results showed that F-HPIDF had a higher water-holding capacity (19.17 g/g), water-swelling capacity (24.83 mL/g), heavy metals-adsorption capacity (Cd2+: 1.82 μmol/g; Pb2+: 1.91 μmol/g; Zn2+: 1.30 μmol/g; Cu2+: 0.68 μmol/g), and harmful substances-adsorption capacity (GAC: 0.23 g/g; CAC: 14.80 mg/g; SCAC: 0.49 g/g) than HPIDF due to the changes of structure caused by fermentation. In addition, with the fermentation of HPIDF, some beneficial substances were produced, which might be potential intestinal prebiotics. The study of F-HPIDF strengthens the speculation that HPIDF may have potential bioactivities after entering the colon, which proved that okara-HPIDF may have potential functionality.

**Keywords:** soybean residue; insoluble dietary fiber; gut microbiota; fermentation in vitro; colon health
