Structure and property of immobilized lipase on chitosan attached to macroporous resin

Transesterification catalyzed by lipase is an available method to produce biodiesel. In order to acquire efficient catalysts used in biodiesel synthesis, a novel immobilized lipase was prepared in this study by using macroporous resin modified by chitosan as the immobilization carrier. Chitosan was attached to macroporous resin prior to lipase immobilization to improve chitosan particles' poor mechanical strength. The structure of the immobilized carrier and lipase was characterized by scanning electron micrograph (SEM) and Fourier transform infrared spectroscopy (FT-IR). SEM demonstrated that the surface of the immobilized carrier was smoother than that of resin, and lipase was distinctly immobilized onto the carrier. FT-IR demonstrated that lipase was immobilized onto the carrier by covalent binding. The activity of immobilized lipase remained 80% of its initial activity after it was kept at 80°C for 1 h, while the activity of free lipase dropped to 35% of its initial activity under the same conditions. After 30 days of storage, the residual activity was 79% for the immobilized lipase higher than 54% for free lipase. Moreover, immobilized lipase was not easily denatured and inactivated in the presence of non-polar organic solvents, but it's the opposite in polar organic solvents. Its hydrolysis rate of olive oil remained 70% after 10 cycles in batch operation. With waste oil as substrate, the esterification rate of the products was achieved about 81%. The synthesis of biodiesel catalyzed by the immobilized lipase in organic media provided the basis for the industrial applications.