Enzymatic activity studies of Pseudomonas cepacia lipase adsorbed onto copolymer supports containing β-cyclodextrin

Abstract

Pseudomonas cepacia lipase (PCL) was immobilized onto polyurethane copolymers containing β-cyclodextrin (β-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 β-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 (∼three-fold for CDI and ∼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 °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 ∼75–80% esterification activity after the fourth catalytic cycle and exhibited appreciable stability for at least 30 days.