Microbial degradation of carbosulfan by carbosulfan - and carbofuran - retreated rice soil suspension

Abstract

The role of microorganisms in the degradation of carbosulfan (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-(di-n-butyl)-aminosulfenyl++ + methyl carbamate), an analogue of carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methyl carbamate) was studied by selective enrichment of microorganisms degrading either or both insecticides by repeated application of the insecticides, individually or in combination to flooded soil. Soil suspension from the pots treated with carbosulfan and carbofuran, individually or in combination collected after two applications, effected distinctly more rapid hydrolysis of carbosulfan than did the suspension from untreated pots or the uninoculated medium. The rate of hydrolysis was further accelerated by soil suspensions collected after six applications of the insecticides in the order carbosulfan treated > carbofuran treated > carbosulfan + carbofuran treated. The ability of treated and untreated suspension to degrade carbofuran was also studied. The rate of degradation of carbofuran by the suspension was in the order carbofuran retreated > carbosulfan + carbofuran retreated > carbosulfan retreated soil. Further involvement of microorganism in the rapid degradation of carbosulfan was confirmed by testing the degradation in sterilized and nonsterilized enrichment culture.

Microbial degradation of two carbamate insecticides and their main metabolites in soil

“…Many authors, in fact, report the capability of soil microrganisms to use the carbamate insecticides (aldicarb and carbofuran and some metabolites) as a source of carbon and nitrogen for growth (Ou et al, 1988;Baron and Merriam, 1988;Rasul Chaudry and Ali, 1988;Sahoo et al, 1998;Salama, 1998). Since in the case of hydroxycarbofuran and ketocarbofuran the differences in bacterial numbers between treated soils and controls are not significant, the degradation might be due to both chemical and co-metabolic processes.…”

“…The degradation of these parent compounds and of their main metabolites has been studied in extensively (Kale et al, 2001;Kazumi and Capone, 1995) and several soil microorganisms have been reported to transform aldicarb and carbofuran Trabue et al, 1997;Sahoo et al, 1998;Salama, 1998) to their main metabolites; however, the biochemical pathways regarding the complete mineralization of the transformation products are still not well known.…”

Nematicidal efficacy, enhanced degradation and cross adaptation of carbosulfan, cadusafos and triazophos under tropical conditions

“…Accelerated biotransformation has also been evinced for aldicarb (Read, 1987;Suett & Jukes, 1988), carbofuran (Harris et al, 1984;Read, 1986;Suett, 1986Suett, , 1987Racke & Coats, 1988b, Morel-Chevillet et al, 1996Karpouzas et al, 2000a), carbosulfan (Sahoo et al, 1990(Sahoo et al, , 1998, cadusafos (Anderson et al, 1998;Karpouzas et al, 2004), ethoprophos and oxamyl (Smelt et al, 1987;Karpouzas et al, 1999Karpouzas et al, , 2000b, fenamiphos (Ou, 1991;Chung & Ou, 1996;Pattison et al, 2000) and terbufos (Felsot, 1998).…”

Comparison of four mass analyzers for determining carbosulfan and its metabolites in citrus by liquid chromatography/mass spectrometry

“…The occurrence of carbamates and their transformation products (TPs) in fruits is, presently, an important concern because some processes, such as hydrolysis, biodegradation, oxidation, photolysis, etc., implicated in their disappearance can lead to compounds that are more toxic than the parent pesticides 1–4. A typical example of this problem is carbosulfan, which degrades to carbofuran and 3‐hydroxycarbofuran; the former compound is more toxic than carbosulfan, while the metabolites are rather persistent 5, 6. This pesticide has a temporary acceptable daily intake (ADI) of 0.01 mg kg −1 body weight (bw) and a maximum residue limit (MRL) of 0.05 mg kg −1 for the sum of carbosulfan, carbofuran and 3‐hydroxycarbofuran in citrus fruits 7, 8…”