Enrichment of two isoflavone aglycones in black soymilk by using spent coffee grounds as an immobiliser for β-glucosidase

► A catalytic system for deglycosylation of isoflavone in soymilk was established. ► Immobilised β-glucosidase performed effectively on isoflavone conversion. ► The kinetic parameters including KM, Vmax, K, τ50 were determined. ► This enzyme system took only 60 min to achieve complete isoflavone deglycosylation. ► 30 reuses and 20-day storage are suggested for this immobilised enzyme system.