Laccase immobilized polyacrylamide-alginate cryogel: A candidate for treatment of effluents

Enzyme immobilization is a promising technique for several purposes including biotechnology, medicine, biochemistry and environment. Laccase is one of the intensely studied enzyme in immobilization research. In this study, laccase enzyme from Trametes versicolor was immobilized on glycidyl methacrylate (GMA) functionalized polyacrylamide-alginate cryogel (PAG). Characterization of the cryogel was carried out by Fourier transform infrared spectrometry, environmental scanning electron microscopy, energy dispersive X-ray analysis, surface area analysis by Brunauer-Emmett-Teller technique and swelling test. Laccase enzyme was immobilized covalently and maximum loading (68.7 ± 1.45 mg/g) occurred at pH 3.0 and 25 °C. Activities of free and immobilized laccase enzymes were measured using three substrates, 2,2ˈ-azinobis-(3-ethylbenzothiazoline-6-sulfonate, syringaldazine and guaiacol. Optimum pH, optimum temperature and kinetic parameters were calculated with each substrate. Stability of immobilized laccase enzyme due to temperature rise, storage duration and repeated use was demonstrated to be higher than free laccase enzyme. Immobilized laccase was also utilized for decolorization of dyes, dephenolization of olive mill wastewater (OMW) and treatment for a textile effluent. It was demonstrated that immobilized laccase enzyme removed 70.0 ± 1.2 % of phenolic compounds in OMW, successfully. Additionally, 55.6 ± 0.72 % of removal of dyes from textile wastewater and 93.3–99.1 % decolorization of some selected dyes in solution was observed.