Enhanced biotransformation of soybean isoflavone from glycosides to aglycones using solid-state fermentation of soybean with effective microorganisms (EM) strains.

To improve the biotransformation efficacy (BE) of glycosides to aglycones in total soybean isoflavone (SIF), Taguchi experimental design has been used to study the most significant factors on BE of glycosides to aglycones using solid-state fermentation (SSF) of soybean with effective microorganisms (EM) strains. Physicochemical properties of optimized fermented dregs have also been analyzed to evaluate their probiotics count and mainly nutritional parameters. The results showed that identified optimal fermentation conditions are 30°C, 40% water content, 5% inoculation level, 6 d culture time, and 20 mesh number. BE of aglycones reached 85.30% with dry matter recoveries of 96.34% based on optimal fermentation conditions. Total bacterial and lactic acid bacteria count reached 17.98 and 9.34 × 108 CFU/g with decreasing pH (4.21) and an increasing acidity (8.62 g/kg), respectively. This study could provide the theoretical grounds for aglycones biotransformation in large-scale production applied in food and other fields. PRACTICAL APPLICATIONS: Isoflavones widely present in soy products possessing strong antioxidant capacity and estrogen-like activity. In human intestines, aglycone isoflavones after treatment/fermented are absorbed faster than their glucosides in untreated soybeans. The majority of glucoside isoflavones in soybean during fermentation were biologically converted to bioactive aglycone isoflavones via EM strains-fermented β-glucosidase. SSF of soybean with EM cocultures to ferment soymilk efficiently increased BE of glycosides to aglycones. Hence, EM cocultures as a new functional ingredient could improve the nutritional value of fermented soybean.