Immobilization of pectin lyase from Penicillium italicum by covalent binding to nylon

Pectin lyase [PNL, poly(methoxygalacturonide) lyase; E.C. 4.2.2.10] from Penicillium italicum was immobilized by covalent binding to Nylon 6 in order to compare physico-chemical and kinetic properties of the soluble and immobilized counterpart. Optimum conditions for the immobilization process, kinetic parameters, and pH and temperature behavior of the enzyme were determined. The pH activity curve of the immobilized enzyme shifted toward a low pH compared with that of the soluble one. Similarly, the immobilized PNL was more stable at lower pHs than the soluble enzyme. The immobilization caused a marked increase in the thermal stability of the enzyme. The immobilized PNL was extraordinarily stable during storage at 4 degrees C. No loss of activity was observed when the immobilized enzyme was used for 12 consecutive cycles of operation. In comparison with the soluble enzyme, the immobilized PNL caused a lower decrease in the viscosity of pectin solutions. Nevertheless, when fruit juices were used, the drop in initial viscosity was as marked as that observed when the soluble enzyme was used to clarify pectin solutions. Nylon-immobilized PNL appears promising for the clarification of fruit juices at 40 degrees C and approximate pH of 3.0.