Associations between isoflavone composition and enzyme inhibition in Cheonggukjang upgraded by mycelial co-fermentation

In this study, Cheonggukjang was processed by combining soybean germination with mycelial co-fermentation using Bacillus subtilis and liquid cultures of Lentinula edodes, Pleurotus ostreatus, and Ganoderma lucidum. Across non-germinated, germinated, and mycelial variants, β-glucosidase activity, isoflavone aglycones, and in-vitro α-glucosidase and α-amylase inhibition were profiled. Mycelial Cheonggukjangs showed high α-glucosidase inhibition accompanied by substantial α-amylase inhibition, indicating strong dual inhibition without pronounced selectivity. Total aglycones tended to associate with higher α-glucosidase inhibition. Exploratory chemometrics (PLS-R) prioritized β-glucosidase activity and glycitein as influential variables, and simple mediation analysis suggested that part of the association between β-glucosidase and α-glucosidase inhibition may be transmitted via aglycone accumulation. Overall, these findings characterize mycelial fermented Cheonggukjang as a dual inhibitor of carbohydrate-hydrolyzing enzymes and provide exploratory, correlation based evidence that higher β-glucosidase activity and isoflavone aglycone levels are associated with stronger enzyme inhibition.