Immobilization of laccase on modified chitosan composite, characterization and investigation of the kinetics of color removal of textile dyes by immobilized enzyme.

Reactive dyes are widely used in textile industry due to their bright colors, excellent colorfastness and easy applicability. In recent years, the researches related to utilization of the biological treatment to remove dyes from waste water have increased. In present work, chitosan (Kit) was modified by reduced graphene oxide (RGO), magnetite (Fe3O4) and glutaraldehyde (GA) and obtained Kit-RGO and Kit-RGO-Fe3O4 beads. Chitosan composite beads were characterized by IR, SEM, XRD, TGA and VSM. Laccase from Trametes versicolor (EC 1.10.3.2.) were immobilized on chitosan composite beads and the conditions in which immobilized laccases showed their maximum activities and the kinetic parameters were determined. The thermal stabilities, storage stabilities, effect of inhibitors and organic solvents stabilities of all immobilized laccase preparations were researched and synthetic textile dye, reactive blue 21 was removed by immobilized laccases from aqueous solutions. The immobilization yields and the activities per gram carrier were calculated 55.29 % and 2.372 U g-1 for Kit-RGO, 57.07 % and 2.50 U g-1 for Kit-RGO-Fe3O4, respectively. Optimum pH was found as pH 4.0 for free laccase and found as pH 5.0 for immobilized enzyme, and optimum temperature was found as 40 °C. As a result of the organic solvents studies, thermal stabilities, storage stabilities, effect of inhibitors immobilized laccases were found to be more stable and less inhibited than free laccase. In this study, for effective dye decolorization various parameters were investigated on enzymatic decolorization. Furthermore, phytotoxicity was performed using decolorized dye solution.