Changes in the physicochemical properties and structural characteristics of rice bran polysaccharides extracted by specific enzyme cocktail and ultrasound

To maximize insoluble rice bran fiber, rice bran polysaccharides were extracted from it using ultrasound and specific enzyme-assisted methods. Additionally, the specific enzyme cocktail was also produced by Schizophyllum commune cultivated on insoluble rice bran fiber. Based on response surface methodology, the optimal conditions of specific enzyme-assisted extraction were: temperature 42.8 °C, pH 4.3, and enzyme ratio 10.6 mg/g. Then, a three-step method (ultrasound-enzyme-ultrasound assisted extraction) was used for the extraction of polysaccharides. The rice bran polysaccharide yields from three steps were: 5.57 ± 0.34 %, 4.1 ± 0.05 %, and 0.32 ± 0.03 %, respectively, with molecular weight of 266.73, 4.07, and 22.84 kDa. The rice bran polysaccharides exhibited significant differences in the monosaccharide composition, surface morphological, structural characteristics, and antioxidant activities. Additionally, 186 secretory proteins were detected by proteomic analysis in the enzyme cocktail, including complete cellulases and numerous hemicellulases. These findings provide a sustainable, efficient way to extract rice bran polysaccharides with different properties.