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Improving the activity and stability of Yarrowia lipolytica lipase Lip2 by immobilization on polyethyleneimine-coated polyurethane foam

Cui, Caixia, Tao, Yifeng, Li, Lingli, Chen, Biqiang, Tan, Tianwei
Journal of Molecular Catalysis. B, Enzymatic 2013 v.91 pp. 59-66
Yarrowia lipolytica, catalytic activity, coatings, enzyme activity, enzyme kinetics, enzyme stability, esterification, foams, glutaraldehyde, heat inactivation, heat stability, heat treatment, hexane, immobilized enzymes, polyurethanes, triacylglycerol lipase, triolein
In this study, polyurethane foam (PUF) was used for immobilization of Yarrowia lipolytica lipase Lip2 via polyethyleneimine (PEI) coating and glutaraldehyde (GA) coupling. The activity of immobilized lipases was found to depend upon the size of the PEI polymers and the way of GA treatment, with best results obtained for covalent-bind enzyme on glutaraldehyde activated PEI-PUF (MW 70,000Da), which was 1.7 time greater activity compared to the same enzyme immobilized without PEI and GA. Kinetic analysis shows the hydrolytic activity of both free and immobilized lipases on triolein substrate can be described by Michaelis–Menten model. The Km for the immobilized and free lipases on PEI-coated PUF was 58.9 and 9.73mM, respectively. The Vmax values of free and immobilized enzymes on PEI-coated PUF were calculated as 102 and 48.6U/mg enzyme, respectively. Thermal stability for the immobilization preparations was enhanced compared with that for free preparations. At 50°C, the free enzyme lost most of its initial activity after a 30min of heat treatment, while the immobilized enzymes showed significant resistance to thermal inactivation (retaining about 70% of its initial activity). Finally, the immobilized lipase was used for the production of lauryl laurate in hexane medium. Lipase immobilization on the PEI support exhibited a significantly improved operational stability in esterification system. After re-use in 30 successive batches, a high ester yield (88%) was maintained. These results indicate that PEI, a polymeric bed, could not only bridge support and immobilized enzymes but also create a favorable micro-environment for lipase. This study provides a simple, efficient protocol for the immobilization of Y. lipolytica lipase Lip2 using PUF as a cheap and effective material.