Isolation of a fluoroglycofen-degrading KS-1 strain and cloning of a novel esterase gene fluE

Abstract

The bacterium KS-1, capable of degrading fluoroglycofen, was isolated from sludge collected at a herbicide factory. The isolate was identified as Lysinibacillus sp. according to its phenotypic features and 16S rDNA phylogeny. KS-1 degraded 85.25% of the fluoroglycofen (50 mg L⁻¹) within 3 days of incubation. The optimum temperature and pH for fluoroglycofen degradation were 30°C and 7.0, respectively. Furthermore, Zn²⁺ and Cu²⁺ could significantly decrease the degradation rate. Three degradation products, which appeared during KS-1-mediated fluoroglycofen metabolism, were identified as deethyl-fluoroglycofen, acifluorfen and decarboxylate-acifluorfen. The fluE gene, which encodes a novel esterase that catalyzes the cleavage of carboxyl ester bonds of fluoroglycofen, was cloned from the KS-1 strain. Sequence alignment reveals that FluE shares 30%–40% amino acid sequence identity with members of the hormone sensitive lipase family. FluE was expressed in Escherichia coli BL21 and purified by Ni-NTA affinity chromatography. Purified FluE could efficiently hydrolyze fluoroglycofen and short-chain p-nitrophenol esters. However, no lipolytic activity was observed with esters containing acyl chains longer than 10 carbon atoms, thereby indicating that this enzyme is an esterase.

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