Accumulation of Soybean Glyceollins Induced by Solid-state Fermentation and Antioxidant Activity Evaluation
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Abstract:
Soybean glyceollin is a member of the phytoalexin family, and shows estrogen receptor modulator activity. Therefore, it has been used to control and prevent postmenopausal osteoporosis. In this study, using Nannong 99-6 soybean as the raw material, the conversion of soybean glucosidic isoflavones into aglycone and glyceollins, and the accumulation of aglycone and glyceollins were achieved by screening food-grade fungal strains and optimizing the solid-state fermentation process. Furthermore, the in vivo antioxidant activity of fermented soybean was evaluated. The results indicated that stimulation by microbial elicitors could result in the successful conversion of isoflavone to aglycone and glyceollins, and in the consequent accumulation of aglycone and glyceollins in soybeans. Moreover, the conversion efficiency was influenced by inoculation conditions (microorganism species, inoculation concentration, fermentation time, injury treatment, and germination pretreatment). The optimal solid-state fermentation process to obtain aglycone- and glyceollins-rich soybean-fermented products was to carry out the solid-state fermentation of soybeans with Aspergillus oryzae CICC2436 at a spore concentration of 107/g soybeans for three days. Moreover, the injury and germination pretreatments were also conducive to the conversion of soybean isoflavone, but the accumulation of glyceollins was mainly affected by the elicitor–injury treatment. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging rate and ferric-reducing power value confirmed the high in vitro antioxidant activity of fermented soybean.
