Characteristics of Crosslinking Polymers Play Major Roles in Improving the Stability and Catalytic Properties of Immobilized Thermomyces lanuginosus Lipase.

Yuhong Mao,Chenxi Zhou,Xiuyun Ye,Zhenling Cai,Hangzhen Lan

doi:10.3390/ijms23062917

Abstract

This study aimed to improve the stability and catalytic properties of Thermomyces lanuginosus lipase (TLL) adsorbed on a hydrophobic support. At the optimized conditions (pH 5 and 25 °C without any additions), the Sips isotherm model effectively fitted the equilibrium adsorption data, indicating a monolayer and the homogenous distribution of immobilized lipase molecules. To preserve the high specific activity of adsorbed lipase, the immobilized lipase (IL) with a moderate loading amount (approximately 40% surface coverage) was selected. Polyethylenimine (PEI) and chitosan (CS) were successfully applied as bridging units to in situ crosslink the immobilized lipase molecules in IL. At the low polymer concentration (0.5%, w/w) and with 1 h incubation, insignificant changes in average pore size were detected. Short-chain PEI and CS (MW ≤ 2 kDa) efficiently improved the lipase stability, i.e., the lipase loss decreased from 40% to <2%. Notably, CS performed much better than PEI in maintaining lipase activity. IL crosslinked with CS-2 kDa showed a two- to three-fold higher rate when hydrolyzing p-nitrophenyl butyrate and a two-fold increase in the catalytic efficiency in the esterification of hexanoic acid with butanol. These in situ crosslinking strategies offer good potential for modulating the catalytic properties of TLL for a specific reaction.

Highlights

IntroductionThermomyces lanuginosus lipase (TLL) is a versatile biocatalyst, catalyzing various reactions, such as hydrolysis, esterification, transesterification, etc
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This study aimed to improve the stability and catalytic performance of Thermomyces lanuginosus lipase (TLL) adsorbed on a hydrophobic and porous support

Summary

Introduction

Thermomyces lanuginosus lipase (TLL) is a versatile biocatalyst, catalyzing various reactions, such as hydrolysis, esterification, transesterification, etc. To be applied at an industrial scale, an immobilized form of TLL is favored to permit its reuse and easy separation from the reaction mixture. The adsorption of lipases on hydrophobic and porous supports has attracted great attention [3–5]. These porous supports offer a sufficient surface area by altering their pore size and porosity, and can be recycled. Lipases adsorbed on these hydrophobic carriers are mostly activated, which is attributed by the so-called “interfacial activation” [3,5]. Bifunctional agents were introduced to generate intermolecular crosslinking with lipases, preventing desorption [3]. The most commonly used one is glutaraldehyde (GA), which requires a sufficient distance between molecules to form intermolecular crosslinking [6]

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