Development of a magnetic β-glucosidase biocatalyst: Structural and functional characterization with enhanced thermal...

β-Glucosidase is an important industrial enzyme, but its application is often limited by low thermal stability and poor operational reusability. In this study, a magnetic material containing β-glucosidase activity was developed through immobilization of a partially purified fungal enzyme onto modified magnetic nanoparticles, enabling rapid and efficient separation of the catalyst from the reaction medium using an external magnetic field. The immobilized enzyme retained 58% of its initial activity after the first catalytic cycle and approximately 20% after four consecutive cycles, demonstrating operational reusability. Both free and immobilized enzymes exhibited an optimal temperature of 60 °C, while immobilization shifted the optimal pH from 6.5 to 5.5 and broadened the effective pH range. The immobilized biocatalyst showed significantly enhanced thermal stability, retaining activity for 280 min at 50 °C, compared to 180 min for the free enzyme, and maintaining activity at 70 °C, where the free enzyme was completely inactivated. Structural and compositional analyses by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis confirmed successful enzyme immobilization. Overall, the magnetic immobilization strategy improved enzyme stability, reusability, and recovery, supporting its potential application in biotechnological processes requiring robust β-glucosidase catalysts.