Comparative Kinetic Study of Phenol Degradation Using Free and Alginate Gel Entrapped Mushroom Tyrosinase

The aim of this study was to investigate the biochemical properties of free and immobilized mushroom tyrosinase (EC 1. 14. 18. 1) entrapped in calcium alginate beads for phenol removal in batch system. Tyrosinase activity was determined spectrophotometrically at 400 nm under optimal conditions. The effects of key operational parameters on phenol oxidation kinetics were evaluated for both enzyme systems. The Michaelis–Menten constant (Km) of the immobilized enzyme (1.04 mM) was approximately twice that of the free enzyme (0.56 mM), while its maximum reaction velocity (Vmax = 139.02 EU) decreased by nearly thirtyfold (Vmax = 5.91 EU). Immobilization also shifted the optimal pH of the enzyme to pH 5.6. Optimum temperature and the activation energy for phenol oxidation were determined as 55°C and 50.4 kJ/mol for immobilized tyrosinase, whereas, 45°C and 39.5 kJ/mol for the free enzyme. The highest activity was obtained with alginate beads of 3.4 mm diameter, and the immobilized preparation exhibited enhanced operational stability, retaining totally its initial activity after 5 reuse cycles. Overall, these findings suggest that mushroom tyrosinase immobilized in alginate beads is a promising system for phenol removal from wastewater.