Abstract
Metolachlor is extensively used and the most persistent chloroacetamide herbicide, thereby which its metabolites have been frequently detected in soils and surface and groundwaters. Microbial degradation is predominantly responsible for the removal of metolachlor from soil and water. However, few microbial strains reported previously are highly efficient in degrading potentials for metolachlor. We isolated the fungal strain MET-F-1 from an activated sludge, characterized as Penicillium oxalicum, which could degrade 88.6% of 50 mg/L metolachlor coupled with 0.1% glucose plus 0.1% yeast extract within 384 h under optimal conditions. Compared with metabolites produced by previously isolated microorganisms, different degradation products, i.e., MOXA, M2H, and MDES, detected by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), were produced through hydrolytic and reductive dechlorination by MET-F-1. This is the first report on the degradation of metolachlor by Penicillium oxalicum sp. Furthermore, field plot experiments using the wheat bran inoculum method were performed and demonstrated good metolachlor-degrading activity of this strain. This study serves as a steppingstone to promote MET-F-1 strain usage as a promising agent for metolachlor-contaminated soil remediation.
Highlights
The application of herbicides in agriculture increases crop yields and threatens the terrestrial and aquatic ecosystems [1,2]
Metolachlor is more recalcitrant toward biodegradation than other chloroacetanilide herbicides due to its longer alkyl chain on the amide nitrogen [18]
Some treatments of co-metabolic culture in MSM medium were designed, using which MET-F-1 was found to have the good ability to degrade metolachlor, whereas the other three strains had no obvious effects on the degradation of metolachlor
Summary
The application of herbicides in agriculture increases crop yields and threatens the terrestrial and aquatic ecosystems [1,2]. Metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy1-methylethyl] acetamide) is one of the most commonly used herbicides, accounting for approximately. 4.2% of the global herbicide usage [3]. It is a highly selective chloroacetamide pesticide which is widely used to control broadleaf grasses and annual weeds in the pre-emergence period of more than 70 different crops, such as corn, soybeans, and cotton, which are the main crops in China [4,5]. In previous studies, high detection rates of metolachlor in surface and groundwaters have been observed because of its higher water solubility (530 mg/L, 20 ◦ C) compared with other chloroacetamide herbicides [9,10,11]
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