Immobilization of Pycnoporus coccineus laccase on Eupergit C:: Stabilization and treatment of olive oil mill wastewaters

The use of olive oil mill wastewaters (OMW) as an organic fertilizer is limited by their phytotoxic effect, due to the high concentration of phenolic compounds. As an alternative to physico-chemical methods for OMW detoxification, the laccase from Pycnoporus coccineus, a white-rot fungus with the ability to decrease the chemical oxygen demand ( COD) and color of the industrial effluent, is being studied. In this work, the P. coccineus laccase was immobilized on two acrylic epoxy-activated resins, Eupergit C and Eupergit C 250L. The highest activity was obtained with the macroporous Eupergit C 250L, reaching 110 U g(-1) biocatalyst. A substantial stabilization effect against pH and temperature was obtained upon immobilization. The soluble enzyme maintained >= 80% of its initial activity after 24 h at pH 7.0 - 10.0, whereas the immobilized laccase kept the activity in the pH range 3.0 - 10.0. The free enzyme was quickly inactivated at temperatures 50 degrees C, whereas the immobilized enzyme was very stable up to 70 degrees C. Gel filtration profiles of the OMW treated with the immobilized enzyme ( for 8 h at room temperature) showed both degradation and polymerization of the phenolic compounds.