Lipase immobilization on glutaraldehyde-activated nanofibrous membranes for improved enzyme stabilities and activities

Poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membranes were successfully fabricated and activated with glutaraldehyde (GA) to interact with enzyme molecules. A lipase isolated from Candida rugosa was employed as a model biocatalyst and successfully immobilized onto the membrane surfaces via covalent bonds with the aldehyde groups. Scanning electron microscopy images revealed that the membranes retained uniform nanofibrous and open porous structures after the treatments. The results indicated that the increment of the initial glutaraldehyde concentration induced an increase of the enzyme loading on the membrane surfaces but a decrease in the activity of the immobilized enzyme. Under an optimum condition, the glutaraldehyde activated PVA-co-PE nanofibrous membrane reached the highest enzyme activity at 676.19 U/g of the membrane. The pH tolerance, thermal and storage stability of the immobilized lipase were significantly improved. In addition, the immobilized lipase can be easily recovered and retained at 67% of its initial activity after 10 time uses. Therefore, the glutaraldehyde activated PVA-co-PE nanofibrous membrane is a promising solid support media for enzyme immobilization, and the immobilized enzymes could have broad biocatalytic applications.