Detoxification of diphenyl ether herbicide lactofen by Bacillus sp. Za and enantioselective characteristics of an esterase gene lacE

- Lactofen degrading strain Za belonging to the genus Bacillus was isolated.
- The degrading end-product aminoacifluorfen showed almost no phytotoxicity to maize.
- Gene lacE encoding a lactofen-hydrolyzing esterase was cloned and expressed.
- The (S)-(+)-lactofen was degraded faster than the (R)-(−)-lactofen by LacE.

A bacterial strain Za capable of degrading diphenyl ether herbicide lactofen was isolated and identified as Bacillus sp. This strain could degrade 94.8% of 50 mg L−1 lactofen after 4 days of inoculation in flasks. It was revealed that lactofen was initially hydrolyzed to desethyl lactofen, which was further transformed to acifluorfen, followed by the reduction of the nitro group to yield aminoacifluorfen. The phytotoxicity of the transformed product aminoacifluorfen to maize was decreased significantly compared with the lactofen. A gene lacE, encoding an esterase responsible for lactofen hydrolysis to desethyl lactofen and acifluorfen continuously, was cloned from Bacillus sp. Za. The deduced amino acid belonging to the esterase family VII contained a typical Ser-His-Asp/Glu catalytic triad and the conserved motifs GXSXG. The purified recombinant protein LacE displayed maximal esterase activity at 40 °C and pH 7.0. Additionally, LacE had broad substrate specificity and was capable of hydrolyzing p-nitrophenyl esters. The enantioselectivity of LacE during lactofen degradation was further studied, and the results indicated that the (S)-(+)-lactofen was degraded faster than the (R)-(−)-lactofen, which could illustrate the reported phenomenon that (S)-(+)-lactofen was preferentially degraded in soil and sediment.