Immobilization of lipase on epoxy-activated Purolite((R)) A109 and its post-immobilization stabilization

Abstract

In this study, Purolite (R) A109, polystyrenic macroporous resin, was used as immobilization support due to its good mechanical properties and high particle diameter (400 mu m), which enables efficient application in enzyme reactors due to lower pressure drops. The surface of support had been modified with epichlorhydrine and was tested in lipase immobilization. Optimized procedure for support modification proved to be more efficient than conventional procedure for hydroxy groups (at 22 degrees C for 18 h), since duration of procedure was shortened to 40 min by performing modification at 52 degrees C resulting with almost doubled concentration of epoxy groups (563 mu mol g(-1)). Lipase immobilized on epoxy-modified support showed significantly improved thermal stability comparing to both, free form and commercial immobilized preparation (Novozym (R) 435). The highest activity (47.5 IU g(-1)) and thermal stability (2.5 times higher half-life than at low ionic strength) were obtained with lipase immobilized in high ionic strength. Thermal stability of immobilized lipase was further improved by blocking unreacted epoxy groups on supports surface with amino acids. The most efficient was treatment with phenylalanine, since in such a way blocked immobilized enzyme retained 65% of initial activity after 8 h incubation at 65 degrees C, while non-blocked derivative retained 12%.