Biodegradation of Chlorsulfuron and Metsulfuron‐Methyl byAspergillus nigerin Laboratory Conditions

Abstract

Two sulfonylurea herbicides, chlorsulfuron and metsulfuron-methyl, were studied under laboratory conditions, in order to elucidate the biodegradation pathway operated by Aspergillus niger, a common soil fungus, which is often involved in the degradation of xenobiotics. HPLC-UV was used to study the kinetic of degradation, whereas LC-MS was used to identify the metabolites structure. In order to avoid the chemical degradation induced by a decrease in pH, due to the production of citric acid by the fungus, the experiments were performed in a buffered neutral medium. No significant degradation for both compounds was observed in mineral medium with 0.2% sodium acetate. On the contrary, in a rich medium, after 28 days the degradations, chemical degradation excluded, were about 30% for chlorsulfuron and 33% for metsulfuron-methyl. The main microbial metabolites were obtained via cleavage of the sulfonylurea bridge. In addition the fungus seems to be able to hydroxylate the aromatic ring of chlorsulfuron. In the case of metsulfuron-methyl the only detected metabolite was the triazine derivative, while the aromatic portion was completely degraded. Finally, the demethylation of the methoxy group on the triazine ring, previously observed with a Pseudomonas fluorescens strain, was not observed with A. niger.

Biodegradation of thifensulfuron-methyl by Ochrobactrum sp. in liquid medium and soil

“…Compound A was identified as methyl 3-(N-carbamoylsulfamoyl) thiophene-2-carboxylate. According to previous reports, cleavage of the sulfonylurea bridge was apparently a common or the main degradation pathway for sulfonylurea herbicides, yielding the corresponding sulfonamide and a heterocyclic amine, as reported in the degradation of sulfonylurea herbicides by bacteria and fungi (Boschin et al 2003;Gu et al 2007). Compound B (RT, 10.6 min) showed a molecular ion peak at m/z 372.7 ([M-CH 3 ] ? )…”

“…There are many microorganisms isolated from soils or water that can degrade sulfonylurea herbicides (Boschin et al 2003;Xu et al 2009;Song et al 2013). However, research on the biodegradation of thifensulfuron-methyl is limited.…”

The residual effects of bensulfuron-methyl on growth and photosynthesis of soybean and peanut

“…The use of BSM in southeast China, California, Japan, and many other areas in the world as a herbicide in rice paddies has steadily increased over the past several years (Sarmah et al 1998, Sabater et al 2002, making great contributions to crop protection and production. However, BSM is neither particularly volatile nor photodegradable (Boschin et al 2003, Si et al 2004) and therefore may persist for a long time (over 100 d) when applied under specific climatic and/or soil conditions (Blair and Martin 1998) and can be leached into the environment or its residues may damage other crops in the rotation (Si et al 2004).…”

Persistência de trifloxysulfuron-sodium e pyrithiobac-sodium em diferentes tipos de solo

“…A degradação desse grupo de herbicidas ocorre mais rapidamente em solo não estéril que em solo estéril (Boschin et al, 2003). Devido à capacidade de dissociação em função da variação do pH, herbicidas com características de ácidos fracos também apresentam outras propriedades além da sorção, como a solubilidade e a persistência, que variam em função da acidez do meio.…”