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Construction of Thermophilic Lipase-Embedded MetalOrganic Frameworks via Biomimetic Mineralization: a Biocatalyst for Ester Hydrolysis and Kinetic Resolution Hongming He, Haobo Han, Hui Shi, Yuyang Tian, Fuxing Sun, Yang Song, Quanshun Li, and Guangshan Zhu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b05538 • Publication Date (Web): 31 Aug 2016 Downloaded from http://pubs.acs.org on September 1, 2016
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ACS Applied Materials & Interfaces
Construction of Thermophilic Lipase-Embedded Metal-Organic Frameworks via Biomimetic Mineralization: a Biocatalyst for Ester Hydrolysis and Kinetic Resolution
Hongming He,† Haobo Han,‡ Hui Shi,‡ Yuyang Tian,† Fuxing Sun,† Yang Song,† Quanshun Li,*,‡, and Guangshan Zhu*,†
†
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China.
‡
Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun 130012, P. R. China.
*Corresponding authors. E-mail:
[email protected] (G.Z.);
[email protected] (Q.L.). Tel.: +86-431-85168887; Fax: +86-431-85168331.
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ABSTRACT: Enhancing the activity and stability of enzymes and improving their reusability are critical challenges in the field of enzyme immobilization. Here we report a facile and efficient biomimetic mineralization to embed thermophilic lipase QLM in zeolite imidazolate framework-8 (ZIF-8). Systematic characterization indicated that the entrapment of lipase molecules was successfully achieved during the crystal growth of ZIF-8 with an enzyme loading of ca. 72.2 ± 1.88 mg/g lipase@ZIF-8, and the enzymes could facilitate the construction of framework building blocks. Then the composite lipase@ZIF-8 was observed to possess favorable catalytic activity and stability in the ester hydrolysis, using the hydrolysis of p-nitrophenyl caprylate as a model. Finally, the composite was successfully applied in the kinetic resolution of (R, S)-2-octanol, with favorable catalytic activity and enantioselectivity during 10 cycle reactions. Thus, the biomimetic mineralization process can be potentially used as an effective technique for realizing the entrapment of biomacromolecules and constructing efficient catalysts for industrial biocatalysis. KEYWORDS:
Thermophilic
lipase;
Metal-organic
frameworks;
Biomimetic
mineralization; Ester hydrolysis; Kinetic resolution
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ACS Applied Materials & Interfaces
1. INTRODUCTION Lipases (triacylglycerol hydrolase, EC 3.1.1.3) are an attractive class of enzymes capable of catalyzing ester hydrolysis, esterification and transesterification reactions in the absence of cofactors.1-3 Moreover, lipases can execute a variety of organic reactions under mild conditions due to their high enantio-, chemo- and regioselectivity.4,5 Thus, it is of great significance to develop lipase biocatalysts with excellent properties for manufacturing products such as detergents, food, leather, paper, cosmetics, and bioenergy.6-8 However, there are many factors which limit the practical applications of lipases, such as unfavorable stability against thermal, organic solvents, detergents or metal ions, and unsatisfactory reusability. For overcoming these disadvantages, exploring enzymes from thermophiles is a promising strategy for achieving their applications in industrial biocatalysis owing to their high catalytic activity and stability under harsh reaction conditions.9 For instance, thermophilic lipase QLM from Alcaligenes sp. has been demonstrated to possess high hydrolytic activity towards a variety of esters and excellent thermostability with an optimal temperature of 65-70 o
C.10 In addition, it has been successfully used in the kinetic resolution of racemic
compounds through enantioselective hydrolysis, esterification or transesterification.11,12 The enzyme immobilization is another simple and efficient method for solving the problems mentioned above, as it can not only address the issue of stability and reusability but also improve the control of enzymatic reactions.13-15 Typically, physical adsorption or entrapment and covalent attachment are the main methods to immobilize
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lipases on the solid supports. Unfortunately, for physical adsorption or entrapment methods, enzymes are easy to leach out from the solid supports due to their weak interaction with the supports.16 In covalent attachment method, introducing functional coupling groups (e.g., -NH2, -COOH or -SH) for surface modification is always needed for preventing the leakage of enzymes, which will inevitably influence the enzymes’ conformation and catalytic activity and also cause additional costs and environmental pollution.17 Recently, the application scope of porous nanomaterial metal-organic frameworks (MOFs) has been extended from gas storage and chemical catalysis to enzyme immobilization in an entrapment manner.18-26 In these studies, enzymes in MOFs showed exceptional properties, including extremely high stability and resistance against high temperature, organic solvents or proteases. Nevertheless, these immobilization methods including physical adsorption or encapsulation of enzymes into extremely large pores could not achieve the size control of enzyme-MOF composites and efficiently retain the enzymatic activity due to the destabilization of enzymes’ conformation induced by MOFs. In addition, small pore size (
