Fabrication and Catalytic Characterization of Laccase-Loaded Calcium-Alginate Beads for Enhanced Degradation of Dye-Contaminated Aqueous Solutions

Engineered laccases represent an eco-friendlier and robust biocatalytic tool for the treatment of dye-harboring textile wastewater. This study investigates the immobilization of purified laccase from Pleurotus sapidus onto firm-quality spherical Ca-alginate beads by a cross-linking approach. Sodium alginate at an optimal concentration of 4% (w/v) furnished the highest immobilization efficiency (69%). EDX analysis confirmed the detection of copper in the laccase-incorporated alginate beads. The optimum pH for free laccase was 3.0, while the Ca-alginate-Lac showed the maximum enzyme activity (440.2 U/mL) at pH 5.0. In contrast to a free enzyme (40 °C), immobilized laccase performed best at an elevated temperature of 65 °C. The Km and Vmax values in the case of free and Ca-alginate immobilized enzymes were 114 µM, 370 U/mL, and 123 µM, 548 U/mL, respectively. Immobilized laccase catalyzed a highly efficient decolorization of various reactive and disperse dye pollutants and recorded in the range of 86.19–91.01%. The COD and TOC levels were substantially reduced to 91.90–94.94 and 77.01–93.29%, respectively, in the maximally degraded dye solutions. Therefore, immobilization of laccase on Ca-alginate beads offers a cost-effective and facile method for environmental remediation applications.