Catalytic, Kinetic, and Thermodynamic Properties of Pleurotus Ostreatus NØ 3501 Laccase Immobilized on Clinoptilolite Nanoparticles and its Application in Dye Decolorization

Laccase from Pleurotus ostreatus was immobilized on different nanoparticles by physical adsorption and covalent binding. The immobilized enzyme on Na-clinoptilolite nanoparticles showed the highest recovered activity (71.75%) and thermal stability. X-Ray diffraction, surface morphology and the internal structure of the immobilization carrier (Na-clinoptilolite nanoparticles) were investigated. Compared to the free enzyme, the immobilized preparation exhibited higher optimum temperature, lower activation energy ( Ea ), lower deactivation constant rate ( kd ), higher t 1/2 and higher decimal reduction time values ( D ) within the temperature range of 50 -70 degrees C. The thermodynamic parameters ( dH*, dG*, dS* ) of irreversible thermal denaturation for the free and immobilized laccase were also evaluated. The values of enthalpy of activation ( d H*), and free energy of transition state binding ( d G* E-T ) for substrate catalysis were lowered for the immobilized enzyme. Moreover, there was highly significant impact on improving the values of V max /K m , k cat , k cat /K m , and d G* E-S for the immobilized enzyme. The immobilized laccase from Pleurotus ostreatus NRRL 3501 on Na-clinoptilolite nanoparticles was evaluated for dye decolorization. In batch experiments the immobilized enzyme was able to decolorize the following dyes R. Blue 203 (97%), A. red 299 (100%), and Acid mix (89%) after incubation for 120 min. In repeated use the immobilized enzyme was able to decolorize the dye mixture for 8 continuous cycles.