Structure, physicochemical, and functional properties of insoluble dietary fiber obtained from Lactobacillus johnsonii-fermented rice bran

johnsonii 4, L. johnsonii 23, and L. johnsonii 46 were utilized to ferment the rice bran respectively and insoluble dietary fiber (IDF) was prepared before and after fermentation, named RBDF-CN, RBDF-04, RBDF-23, and RBDF-46. The results indicated that L. johnsonii 46 was more effective in converting rice bran IDF to soluble dietary fiber than L. johnsonii 4 and L. johnsonii 23. SEM and FT-IR analysis showed that fermentation treatment increased the pore structure and binding sites of rice bran IDF. The fermentation process did not modify the crystalline structure of rice bran insoluble dietary fiber. The TGA results showed that the residual mass fraction of RBDF-46 is 25.00%, higher than that of RBDF-CN (20.11%), RBDF-04 (21.22%), and RBDF-23 (23.36%), indicating superior thermal stability of RBDF-46. In addition, RBDF-46 exhibited elevated OHC, GAC, and SAC levels. RBDF-04 and RBDF-23 exhibited greater SAC and AIC relative to RBDF-CN, The AIC of RBDF-04 (29.99%) was markedly exceeding that of RBDF-CN (9.97%) and RBDF-23 (24.12%), but showing no significant difference compared to RBDF-46 (26.19%). In summary, the fermentation of L. johnsonii 46 enhanced the physicochemical and functional qualities of rice bran IDF, establishing a scientific basis for its use in health foods. • Insoluble dietary fiber was obtained by the action of Lactobacillus johnsonii on rice bran. • Fermentation treatment enhanced the antioxidant activity of IDF from rice bran. • RBDF-46 had superior OHC, GAC, CAC, SAC and AIC in vitro. • RBDF-46 had looser structure and more active groups were exposed on the surface.