Identification and immobilization of a novel cold-adapted esterase, and its potential for bioremediation of pyrethroid-contaminated vegetables

Xinjiong Fan,Yanfang Li,He Li,Xiaolong Liu,Weiqu Liang

doi:10.1186/s12934-017-0767-9

Abstract

BackgroundPyrethroids are potentially harmful to living organisms and ecosystems. Thus, concerns have been raised about pyrethroid residues and their persistence in agricultural products. To date, although several pyrethroid-hydrolyzing enzymes have been cloned, very few reports are available on pyrethroid-hydrolyzing enzymes with cold adaptation, high hydrolytic activity and good reusability, indispensable properties in practical bioremediation of pyrethroid-contaminated vegetables.ResultsHere, a novel gene (est684) encoding pyrethroid-hydrolyzing esterase was isolated from the Mao-tofu metagenome for the first time. Est684 encoded a protein of 227 amino acids and was expressed in Escherichia coli BL21 (DE3) in soluble form. The optimum temperature was 18 °C. It maintained 46.1% of activity at 0 °C and over 50% of its maximal activity at 4–35 °C. With the goal of enhancing stability and recycling biocatalysts, we used mesoporous silica SBA-15 as a nanometer carrier for the efficient immobilization of Est684 by the absorption method. The best conditions were an esterase-to-silica ratio of 0.96 mg/g (w/w) and an adsorption time of 30 min at 10 °C. Under these conditions, the recovery of enzyme activity was 81.3%. A large improvement in the thermostability of Est684 was achieved. The half-life (T1/2) of the immobilized enzyme at 35 °C was 6 h, 4 times longer than the soluble enzyme. Interestingly, the immobilized Est684 had less loss in enzyme activity up to 12 consecutive cycles, and it retained nearly 54% of its activity after 28 cycles, indicating excellent operational stability. Another noteworthy characteristic was its high catalytic activity. It efficiently hydrolyzed cyhalothrin, cypermethrin, and fenvalreate in pyrethroid-contaminated cucumber within 5 min, reaching over 85% degradation efficiency after four cycles.ConclusionsA novel cold-adapted pyrethroid-hydrolyzing esterase was screened from the Mao-tofu metagenome. This report is the first on immobilizing pyrethroid-hydrolyzing enzyme on mesoporous silica. The immobilized enzyme with high hydrolytic activity and outstanding reusability has a remarkable potential for bioremediation of pyrethroid-contaminated vegetables, and it is proposed as an industrial enzyme.

Highlights

Pyrethroids are potentially harmful to living organisms and ecosystems
Very few reports are available on pyrethroid-hydrolyzing enzyme with novel characteristics, such as cold adaptation and high hydrolytic activity, because such enzymes are rare
We reported the cloning, identification and biochemical characterization of one novel coldadapted pyrethroid-hydrolyzing esterase derived from the Mao-tofu metagenome

Summary

Introduction

Pyrethroids are potentially harmful to living organisms and ecosystems. concerns have been raised about pyrethroid residues and their persistence in agricultural products. Very few reports are available on pyrethroid-hydrolyzing enzyme with novel characteristics, such as cold adaptation and high hydrolytic activity, because such enzymes are rare. Cold-adapted enzymes exhibit high catalytic efficiency at moderate and low temperatures and are versatile biocatalysts in many applications [11], especially for bioremediation of pyrethroid-contaminated vegetables. Enzyme conformation is largely protected because the adsorption is mainly achieved by either electrostatic interaction or van der Waals’ force [18]. Such bonding is relatively weak, and enzyme leakage from carrier can occur during operational process. A drawback of this strong binding is the risk of a reduction in enzyme activity [19]

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