Effects of fermentation with feruloyl esterase-producing Lactobacillus johnsonii on the composition, structure, physicochemical properties, and in vitro hypoglycemic activity of soluble dietary fiber from rice bran

Soluble dietary fiber (SDF) is a key functional component in rice bran, but its low natural abundance limits its application potential. In this study, two Lactobacillus johnsonii strains with distinct feruloyl esterase (FAE) activities were selected to investigate their effects on the modification of rice bran SDF through fermentation. The results showed that fermentation with the high-FAE strain L. johnsonii 46 (FSDF-46) increased the SDF yield from 6.39% to 11.45%. Structural characterization indicated that fermentation was associated with the formation of a porous structure, reduced particle size, and decreased crystallinity. Furthermore, FSDF-46 exhibited higher water holding capacity (0.87 g/g) and oil holding capacity (3.789 g/g). The glucose adsorption capacity of FSDF-46 increased by 44.8% and 37.52%. In vitro assays showed that FSDF-46 exhibited enhanced inhibitory effects on α-amylase (52.33%) and α-glucosidase (91.63%). These findings suggest a potential role of FAE-related fermentation in dietary fiber modification and provide a basis for the development of value-added products from rice bran.