Covalent Immobilization of β-Glucosidase on Magnetic Spent Coffee Grounds Modified With PAMAM Dendrimers for Enhanced...

The successful application of enzymes in industries encounters challenges related to high costs, stability, and reuse. In this study, β-glucosidase (BGL) was immobilized via a covalent method after the synthesis of different generations (G_0-2) of polyamidoamine (PAMAM) dendrimers modified magnetic spent coffee grounds (SCGs). With the increase in PAMAM generation, BGL immobilization (163.123 and 218.99 mg protein/g support in G₁ and G₂, respectively) on the support increased. Exceptional stability (> 80% residual activity) was observed for immobilized BGL at varying pH (3 to 6) and temperature (30°C to 80°C) after a 2 h incubation period. The higher generations of PAMAM dendrimers were more tolerant to glucose inhibition than the free enzyme. PAMAM G₁ and G₂ generations showed > 75% residual activity at 200 mM glucose concentration compared to free enzyme, with only 50% residual activity at 100 mM glucose concentration. After employing BGL@MSCG₃@G_0-2 for cellobiose hydrolysis, > 69% glucose yield for 10 cycles was maintained.