Synchronous reducing anti-nutritional factors and enhancing biological activity of soybean by the fermentation of edible fungus Auricularia auricula

Auricularia auricula fermentation was performed to reduce anti-nutritional factors, improve nutritional components, and enhance biological activity of soybean. Results showed that the contents of raffinose, stachyose, and trypsin inhibitor were significantly decreased from initial 1.65 g L-1, 1.60 g L-1, and 284.67 μg g-1 to 0.14 g L-1, 0.35 g L-1, and 4.52 μg g-1 after 144 h of fermentation, respectively. Simultaneously, the contents of polysaccharide, total phenolics, and total flavonoids were increased, and melanin was secreted. The isoflavone glycosides were converted to their aglycones, and the contents of glyctin and genistin were decreased from initial 1107.99 μg g-1 and 2852.26 μg g-1 to non-detection after 72 h of fermentation, respectively. After 96 h of fermentation, the IC50 values of samples against DPPH and ABTS radicals scavenging were decreased from 17.61 mg mL-1 and 3.43 mg mL-1 to 4.63 mg mL-1 and 0.89 mg mL-1, and those of samples inhibiting α-glucosidase and angiotensin I-converting enzyme were decreased from 53.89 mg mL-1 and 11.27 mg mL-1 to 18.24 mg mL-1 and 6.78 mg mL-1, respectively, indicating the significant increase in these bioactivities. These results suggested A. auricula fermentation can enhance the nutritional quality and biological activity of soybean, and the fermented soybean products have the potential to be processed into health foods/food additives.