Improved physicochemical and functional properties of dietary fiber from millet bran fermented by Bacillus natto

Millet bran was fermented with Bacillus natto and the changes of structural, physicochemical and functional properties of its dietary fiber were investigated. Results showed that B. natto fermentation enhanced soluble DF content from 2.3% to 13.2%, and soluble DF/insoluble DF ratio from 3.1% to 19.9%. SEM and FTIR assay indicated that fermentation led to the degradation of cellulose and hemicellulose, thereby forming more porous and loose structure and polysaccharides. The binding capacities such as water and oil holding capacity, swelling capacity as well as cholesterol, bile salts, nitrite ion and glucose adsorption capacity were improved, while cation exchange capacity was not significantly changed. The total phenolic content and DPPH free radical scavenging capacity increased significantly. Overall, fermentation of millet bran by B. natto improved the structural and functional properties of its DF, which could be applied as a functional ingredient in food products.