Abstract: Defatted rice bran is rich in dietary fiber and can be considered a good source of dietary fiber. In this study, rice bran insoluble dietary fiber (RBIDF) was obtained from defatted rice bran by sequential enzymatic treatment and evaluated for surface structure, composition and physicochemical properties. In addition, the effects of intervention with RBIDF on the intestinal microbiota of high-fat diet fed rats were investigated in detail. The composition analysis showed that the content of insoluble diet fiber in RBIDF was approximately 64%, and its surface structure was more loose and porous than that of defatted rice bran. RBIDF possessed improved water/oil-holding capacity and good adsorption capacity for glucose and cholesterol, reaching up to approximately 6.4 and 12.8?mg/g, respectively. RBIDF also exhibited excellent antioxidant properties by scavenging hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Intragastric administration of RBIDF could improve changes in the population and composition of gut microbiota caused by high-fat diet, regulating the intestinal microbiota balance. The results suggested that the RBIDF from defatted rice bran presented excellent bioactivity both in vitro and in vivo. This study could provide a theoretical basis for the development and utilization of RBIDF .

Key words: defatted rice bran; insoluble diet fiber; physicochemical properties; intestinal microbiota