Optimum Lipase Immobilized on Diamine-Grafted PVDF Membrane and Its Characterization

A facile and economic modification of polyvinylidene fluoride (PVDF) with an orientation of diamine is presented herein. The physical characterizations of native and diamine-grafted PVDF membranes are analyzed by three different techniques: the ninhydrin test, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The diamine-grafted PVDF is activated by glutaraldehyde for enzyme immobilization. The response surface methodology (RSM) is used to search the optimal immobilization conditions and to understand the significance of the factors affecting the responses of immobilized lipase. The optimal conditions for lipase immobilization are: a reaction time of 90 min, temperature of 35 °C, pH of 6, and an enzyme concentration of 7 mg/mL. An experiment performed under the optimum conditions obtains lipase activity of 60 U per g of membrane. A good agreement between the calculated and experimental values is thereby achieved.