Comparison of biopolymers for immobilization of laccase: Ecotoxicity assessment of azo dye

Laccase from Pleurotus florida was immobilized on agarose/agar/polyacrylamide gel, glass beads and alginate beads. The laccase entrapped agarose gel exhibited 88% of immobilization yield as compared to laccase immobilization on glass bead (72%) and Ba-alginate (50%). The enzyme embodied in agarose gel showed greater storage stability at 16°C as compared to enzyme immobilized on glass beads and alginate method. Among the three substrates, viz., 2,2-azinobis (3-ethylbenzo-thiazoline-6-sulfonate (ABTS), guaiacol and syringaldazine, the laccase oxidation exerted its optimal activity on ABTS. The Vmax, Kcat and Km determined for ABTS were 1.650 μM min , 1.160 s and 0.0025 mM, respectively. Among the immobilized preparations, laccase entrapped in agarose gel showed high decolorizing ability for Reactive Blue (RB) 172 (83%) within 10 min. The decolorization of RB 172 was confirmed by FTIR analysis. The ecotoxicity assessment of RB 172 decolorization was performed using Allium cepa assay.