Enantioselective hydrolysis of (R/S)-Naproxen methyl ester with sol–gel encapculated lipase in presence of calix[n]arene derivatives
ABSTRACT Lipases are enzymes that catalyses a variety of reactions, such esterifications, interesterification and hydrolysis. Several methods have been reported for the immobilization of lipases, such as deposition onto solid supports, covalent binding and encapsulation within a polymer matrix or silica glasses obtained by sol–gel techniques. In this study, the Candida rugosa lipase was encapsulated within a chemically inert sol–gel support prepared by polycondensation by tetraetoxysilane (TEOS) and octyltrietoxysilane (OTES) in the presence and absence of calix[n]arene, calix[n]-NH2 and calix[n]-COOH (n=4, 6, 8) compounds as additives. The catalytic activity of the encapsulated lipases was evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of rasemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system.The results indicated that the particularly calix[4,6]-NH2 and calix-COOH based encapsulated lipases had higher conversion and enantioselectivity compared to the sol–gel free lipase.
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ABSTRACT: Polyacrylonitrile (PAN) nanofiber membranes functionalized with calixarenes (C) were successfully prepared by electrospinning of PAN solutions with addition of various calixarenes. Uniform electrospun C/PAN nanoﬁbers were obtained by incorporating three types of calixarenes into the PAN matrix and characterized by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared (ATR-FTIR), thermal gravimetric analysis (TGA) and X-ray powder diffraction (XRD). The SEM results showed that the addition of calixarenes resulted in a decrease in the diameter of PAN nanofibers. Static adsorption behavior was studied by using C/PAN nanoﬁbers as adsorbent and Congo red and Neutral red as model dye molecules. The adsorption of Congo red onto Amide-Cal-15/PAN nanoﬁbers fitted the second order kinetic model and the apparent adsorption rate constant was 1.1×10-3 gmg 1min-1 at 25 °C. Then, by virtue of electrostatic attraction, as-prepared Au nanoparticles were immobilized on Amide-Cal/PAN nanoﬁbers to form Au/Amide-Cal/PAN composite nanoﬁbers. The catalytic activity of the as-prepared Au/Amide-Cal/PAN composite nanoﬁbers was investigated by monitoring the reduction of Congo red in the presence of NaBH4. The reduction kinetics was explained by the assumption of a pseudo-first-order reaction with regard to Congo red. Au/Amide-Cal/PAN composite nanoﬁbers exhibited high catalytic activity, excellent stability and convenient recycling.Langmuir 08/2013; · 4.38 Impact Factor
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ABSTRACT: Enzymes found in nature have been exploited in industry due to their inherent catalytic properties in complex chemical processes under mild experimental and environmental conditions. The desired industrial goal is often difficult to achieve using the native form of the enzyme. Recent developments in protein engineering have revolutionized the development of commercially available enzymes into better industrial catalysts. Protein engineering aims at modifying the sequence of a protein, and hence its structure, to create enzymes with improved functional properties such as stability, specific activity, inhibition by reaction products, and selectivity towards non-natural substrates. Soluble enzymes are often immobilized onto solid insoluble supports to be reused in continuous processes and to facilitate the economical recovery of the enzyme after the reaction without any significant loss to its biochemical properties. Immobilization confers considerable stability towards temperature variations and organic solvents. Multipoint and multisubunit covalent attachments of enzymes on appropriately functionalized supports via linkers provide rigidity to the immobilized enzyme structure, ultimately resulting in improved enzyme stability. Protein engineering and immobilization techniques are sequential and compatible approaches for the improvement of enzyme properties. The present review highlights and summarizes various studies that have aimed to improve the biochemical properties of industrially significant enzymes.International Journal of Molecular Sciences 01/2013; 14(1):1232-77. · 2.46 Impact Factor
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ABSTRACT: Enzymatic catalysis has been pursued extensively in a wide range of important chemical processes for their unparalleled selectivity and mild reaction conditions. However, enzymes are usually costly and easy to inactivate in their free forms. Immobilization is the key to optimizing the in-service performance of an enzyme in industrial processes, particularly in the field of non-aqueous phase catalysis. Since the immobilization process for enzymes will inevitably result in some loss of activity, improving the activity retention of the immobilized enzyme is critical. To some extent, the performance of an immobilized enzyme is mainly governed by the supports used for immobilization, thus it is important to fully understand the properties of supporting materials and immobilization processes. In recent years, there has been growing concern in using polymeric materials as supports for their good mechanical and easily adjustable properties. Furthermore, a great many work has been done in order to improve the activity retention and stabilities of immobilized enzymes. Some introduce a spacer arm onto the support surface to improve the enzyme mobility. The support surface is also modified towards biocompatibility to reduce non-biospecific interactions between the enzyme and support. Besides, natural materials can be used directly as supporting materials owning to their inert and biocompatible properties. This review is focused on recent advances in using polymeric materials as hosts for lipase immobilization by two different methods, surface attachment and encapsulation. Polymeric materials of different forms, such as particles, membranes and nanofibers, are discussed in detail. The prospective applications of immobilized enzymes, especially the enzyme-immobilized membrane bioreactors (EMBR) are also discussed.BMB reports 02/2011; 44(2):87-95. · 1.63 Impact Factor