In Vitro and In Vivo Assessments of Anti-Hyperglycemic Properties of Soybean Residue Fermented with Rhizopus oligosporus and Lactiplantibacillus plantarum

Soy isoflavones possess antioxidative, anti-inflammatory, anti-diabetic and phytoestrogenic properties. Soybean residue contains a fair amount of nutrients such as glycosylated isoflavones, minerals and dietary fibers, and is a substantial waste product produced from soymilk and tofu manufacturing. A solid-state fermentation of soybean residue by Rhizopus oligosporus or co-inoculated with Lactiplantibacillus plantarum improves the availability of isoflavones and GABA content which is attributed to ameliorated hyperglycemic symptoms in STZ-induced hyperglycemic mice. The effortless solid-state fermentation with present microbial manipulation supports an anti-hyperglycemia value-added application of soybean residue for functional food development. Background: Due to an awareness of the food crisis and with a rapidly rising prevalence of diabetes, recycling the substantial fibrous soybean residue disposed from soy industries has received consideration. Methods: Lactiplantibacillus plantarum was previously screened for active glutamate decarboxylase, and β-glucosidase activities were adopted for the fermenting of soybean residue using a traditional tempeh solid-state fermenting process with fungal Rhizopus oligosporus. Fermented soybean residue was chemically analyzed and functionally assessed in in vitro and in vivo hyperglycemic conditions. Results: A 48 h longer solid-state fermentation of the soybean residue co-inoculated with R. oligosporus and L. plantarum showed improved contents of isoflavone aglycones and GABA which were attributed to augmented antioxidative capacity, lowered ROS level, improved blood biochemistry, and better blood glucose homeostasis in STZ-induced hyperglycemic mice. Conclusion: The advantages of a food industrial effortless fermentation process, and a health nutritional endorsing anti-hyperglycemic value-added property offer a practical alternative in recycled soybean residue.