Entrusting poly(acrylonitrile-co-maleic acid) ultrafiltration hollow fiber membranes with biomimetic surfaces for lipase immobilization

One natural biomacromolecule, gelatin, was tethered on the surface of poly(acrylonitrile-co-maleic acid) (PANCMA) ultrafiltration hollow fiber membrane to fabricate dual-layer biomimetic support for enzyme immobilization in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS). Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to confirm the chemical changes of the modified PANCMA membrane surfaces. Lipase from Candida rugosa was immobilized on this dual-layer biomimetic support using glutaraldehyde (GA), and on the nascent PANCMA membrane using EDC/NHS as coupling agent, respectively. The properties of the immobilized enzymes were assayed and compared with the free one. It was found that there was an increase of the activity retention of the immobilized lipase on the gelatin-modified membrane (49.2%), compared to that on the nascent membrane (33.9%). The kinetic parameters of the free and immobilized lipases, Km and Vmax, were also assayed. In comparison with the immobilized lipase on the nascent membrane, there was a decrease of the Km value and an increase of the Vmax value for the immobilized lipase on the gelatin-modified membrane. Results also indicated that the pH and thermal stabilities of lipases increased upon immobilization. The residual activities of the immobilized lipases were 55% on the gelatin-modified membrane and 62% on the nascent PANCMA membrane, after 10 uses.