Abstract
Pseudomonas cepacia lipase (PCL) was immobilized onto polyurethane copolymers containing beta-cyclodextrin (beta-CD) via physisorption. The polymer bound PCL was characterized using an equilibrium sorption method, Fourier transform infrared (FTIR) spectroscopy with attenuated total reflectance (ATR), Raman spectroscopy, and powder X-ray diffraction (PXRD). The objective of this research was to investigate lipase immobilization onto polyurethane copolymers and an investigation of its enzymatic activity. The copolymers contain beta-CD with two types of crosslinker units: 4,4'-dicyclohexylmethane diisocyanate (CDI) and 4,4'-diphenylmethane diisocyanate (MDI), respectively. Immobilization of PCL resulted in a pronounced increase in catalytic activity and stability of lipase (similar to three-fold for CDI and similar to four-fold for MDI) in comparison with free lipase in aqueous solution. PCL exhibited remarkable hydrolytic activity over a range of pH (5-9) values, temperatures (25-65 degrees C), and solvents (mostly non-polar). The immobilized lipase was further used for the synthesis of n-butyl octanoate ester using n-butanol and octanoic acid. The immobilized lipase was successfully recycled four times while maintaining similar to 75-80% esterification activity after the fourth catalytic cycle and exhibited appreciable stability for at least 30 days. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.