Abstract
An efficient and easy-to-perform method was developed for covalent immobilization of lipase from Burkholderia cepacia (Lipase PS) on hollow silica microspheres (M540) by bisepoxide activation. For immobilization, various bisepoxides of different length, rigidity and hydrophobicity in their linkers were applied to activate the amino groups on the M540 support. Effect of the individual bisepoxides on the catalytic performance of the immobilized Lipase PS was studied by using lipase-catalyzed kinetic resolution (KR) of racemic 1-phenylethanol (rac-1) with vinyl acetate in batch mode. Catalytic activity, enantiomer selectivity, recyclability and thermal stability of the new immobilized Lipase PS biocatalysts were investigated. The optimal enzyme / support ratio with the support activated by the most efficient bisepoxide, i.e. poly(ethylene glycol) diglycidyl ether (PDE), was 1:5. The most efficient Lipase PS on PDE activated M540 showed an almost five fold higher biocatalytic activity value (rbatch = 42.8 U/g) with enhanced selectivity (ee(R)-2 = 99.1 %) to the free form of Lipase PS (rbatch = 9.0 U/g; ee(R)-2 = 98.9 %). The Lipase PS on PDE-M540 was compared to a commercially available immobilized Lipase PS biocatalyst (Lipobond Lipase PS) and also applied in a packed-bed enzyme reactor operated in continuous-flow mode, where the optimal temperature of M540-PDE-PS reached the 70 °C, while the optimum for Lipobond Lipase PS was 50 °C.
Highlights
Biocatalysis is becoming increasingly important as an efficient and green tool for modern organic synthesis [1, 2]
3 Results and discussion In the first set of experiments, six bisepoxides with linkers of different lengths, rigidity and hydrophobicity were selected for surface modification of Matspheres 540 (M540) a support material with good adsorption properties
M540-PS is a preparation made by adsorption, enzyme leaking can occur during the washing steps, which can lead to reduced enzyme activity. These results show stronger interaction of the enzyme with the support activated with poly(ethylene glycol) diglycidyl ether (PDE), but maybe incorrect elimination of the remaining compounds during the washing steps, which led to almost 40 % activity decrease after 5 cycles [61]
Summary
Biocatalysis is becoming increasingly important as an efficient and green tool for modern organic synthesis [1, 2]. Advantages of enzymes as biocatalysts are their high activity, selectivity, specificity and low toxicity combined with their capability to being used under mild reaction conditions and a limited formation of by-products. In spite of all their advantages of the native enzymes, their use as biocatalyst is only rewarding if it is economically viable. Easy denaturation of their molecular structure at high temperatures, at acidic or basic pH or in the presence of several organic solvents may strictly limit their recovered applications. Enzymes are mixed with substrate in a dilute solution and may not be recovered economically and are generally wasted
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