Laccase Immobilized In-Situ Magnetic Cryogel for Dephenolization of Olive Mill Wastewater

Olive mill wastewater (OMW) is one of the major environmental issues due to high amount of phenolic compounds and organic substances. Physical, chemical and biological processes are applied to decrease the concentrations of these compounds; however, more ecofriendly and cost-effective applications are needed. Among biological treatments, enzymes, especially laccase, come to the front for the reduction of phenolic content of OMW. Nevertheless, laccase is often inactivated in harsh conditions, therefore, immobilizing laccase offers an effective alternative. To this aim, a laccase-immobilized cryogel was prepared to improve its stability and to obtain a reusable catalyst. Laccase was covalently-immobilized onto a magnetic poly(HEMA) cryogel decorated with epoxy groups of epichlorohydrin. Insolubilization improved its stability in terms of pH, temperature, storage and reuse. Km and Vmax of free and immobilized laccase were determined as 1.248 μM and 23.75 μM, and 0.450 U/mg and 0.405 U/mg, respectively. Laccase-immobilized cryogel was evaluated for the potential to reduce phenolic compound amount of OMW and resulted in 79% reduction. Effects of enzyme concentration, time and OMW volume on dephenolization were also evaluated.