A value-added approach to improve the nutritional quality of soybean meal byproduct: Enhancing its antioxidant activity through fermentation by Bacillus amyloliquefaciens SWJS22

The action of beta-glucosidase and protease of Bacillus amyloliquefaciens SWJS22 in the fermentation of soybean meal caused a significant increase 1): in total phenolic and flavonoid contents with two-fold or higher, largely associated with daidzein, glycitein, genistein, protocatechuic, and p-hydroxybenzoic, gallic acids; 2): the amount of peptides < 3 kDa, maillard reaction intermediate and maillard reaction product with five-, three- and twenty-one-fold, respectively. The significant increase in the amount of antioxidant components in the lyophilised fermented soybean meal supernatant (LFSMS) was associated with the improved antioxidant activity. Namely, the DPPH radical scavenging activity, reducing power, and oxygen radical absorbance capacity of the LFSMS generally increased, and LFSMS (at doses > 250 mg/kg body weight) improved the activities of superoxide dismutase, glutathione peroxidase, catalase and total antioxidant capacity, and inhibited the formation of malondialdehyde in mouse serum and liver (p < 0.05). Therefore, LFSMS could be used as functional food ingredients.