Enzyme immobilization enhances the catalytic activity and stability of the enzyme, and also improves reusability. Metal organic frameworks (MOFs), which possess diversified structures and porosity, have been used as excellent carriers for enzyme immobilization. Pseudomonas fluorescens lipase (PFL) has been successfully immobilized onto MOFs by covalent cross-linking to obtain a series of immobilized lipase (PFL@MOFs). PFL@MOFs are used for catalytic enantioselective hydrolysis of 2-(4-hydroxyphenyl) propionic acid ethyl ester enantiomers (2-HPPAEE) in aqueous medium and transesterification of 4-methoxymandelic acid enantiomers (4-MMA) in organic medium. The experimental results indicated that PFL@Uio-66(Zr) exhibits excellent enzymatic catalysis performances and high enantioselectives. In addition, to increase catalytic activity and reusability, PFL is modified by the polyethylene glycol (PEG) to prepare PEG-modified lipase (PFL-PEG), then PFL-PEG is immobilized onto Uio-66(Zr) to prepare PFL-PEG@Uio-66(Zr), demonstrating better reusability and catalytic activity compared with PFL@Uio-66(Zr).
A new heterogeneous bio-catalyst was prepared by the immobilization of pseudomonas fluorescens lipase (PFL) onto metal-organic frameworks (MOF), NH2-MIL-53(Fe), using covalent cross-linking. The immobilized lipase [PEG-PFL@NH2-MIL-53(Fe)] was firstly applied for enantioselective transesterification of (R,S)-4-fluoromandelic acid (4-FMA) with acyl acetate. The effects of temperature, substrate ratio, and reaction time on conversion rates and enantiomer excess were investigated. Experimental results show that the catalytic activity, enantioselectivity, and the thermal stability of PFL are significantly improved by polyethylene glycol (PEG) modification and immobilization. By optimizing the reaction conditions, the excellent results were obtained with conversion of 49.6% and enantiomer excess of 98.0% for the immobilized PFL catalyzed transesterification reaction. Furthermore, the immobilized lipase possesses excellent reusability with 83% of its initial activity after four cycles.