Immobilization of Pseudomonas cepacia lipase onto the electrospun PAN nanofibrous membranes for transesterification reaction

Pseudomonas cepacia lipase was immobilized onto the electrospun polyacrylonitrile (PAN) nanofibrous membrane with covalent binding by activating the nitrile groups of PAN using the amidination reaction successfully. The fiber diameters of initial PAN nanofibers were between 150 and 300 nm. The lipase molecules (1-2 μm) were observed to be attached onto the nanofiber surfaces. After 5 min activation and 30 min reaction with lipase solution, the protein loading has reached saturation point and the immobilized lipase retained 79% activity compared to that of free lipase. The kinetic parameters, K _m and V_max, were determined to be 56.7 mM and 22.5 U/mg for free lipase and 88.4 mM and 18.3 U/mg for immobilized lipase. To compare with free lipase, the pH stability of immobilized lipase was improved significantly in the acidic conditions and the thermal stability of immobilized lipase still maintained 90% of initial specific activity when the temperature achieved 70 °C. After being stored at 30 °C for 20 days, the immobilized lipase kept almost 100% of its initial specific activity. For reusability test, the immobilized lipase still retained 98% of its original specific activity after 10 batch cycles. These results show that the proposed scheme for lipase immobilization has potential in industrial transesterification reaction such as biodiesel production.