Immobilization of Candida rugosa lipase on glutaraldehyde-activated polyester fiber and its application for hydrolysis of some vegetable oils

Abstract

Candida rugosa lipase was effectively immobilized on the poly(ethylene terephthalate) grafted acrylamide (PET-g-AAm) fiber which was prepared through Hofmann reaction. The activities of the immobilized enzyme and the free enzyme were investigated in the hydrolysis reaction of olive oil in isooctane–water biphasic medium. The activities of the free and the immobilized lipases were measured at different pH values, and temperatures. The thermal stability and storage stability of them were also determined. The kinetic parameters of the free and the immobilized lipases, Km and Vmax were calculated, as well. Moreover, the application of immobilized lipase to the hydrolysis of different vegetable oils was realized. The effect of organic solvents on olive oil hydrolysis was examined and time course of the oil hydrolysis was studied. The optimum pH was shifted from 6 to 7 by immobilization of the enzyme. The maximum activity of the free and the immobilized enzymes occurred at 40 °C. It was found that the immobilized lipase stored at 4 °C retained 90% of its original activity after 60 days, whereas the free lipase stored at 4 °C retained 75% of its activity after the same period. In addition, the immobilized lipase exhibited as 0.06 U of the remaining activity even after 10 times reuses. Kinetics studies show that the corresponding values of Km and Vmax were 47.2 mg ml−1 and 48.1 U mg−1 protein for free lipase and 151.6 mg ml−1 and 10.9 U mg−1 protein for immobilized lipase. The immobilized and free enzymes showed similar behavior with respect to the different oil hydrolysis. The time course of the immobilized lipase on canola and olive oils hydrolysis used as substrate was much better than that of the free lipase. A high rate of oil hydrolysis was obtained when isooctane was used as solvent.