Enrichment of a microbial culture capable of degrading endosulphate, the toxic metabolite of endosulfan

Abstract

Aims: The aim of this study was to isolate a source of enzymes capable of degrading endosulphate (endosulfan sulphate), the toxic metabolite of the pesticide endosulfan. Methods and Results: A microbial broth culture capable of degrading endosulphate was enriched from endosulfan-contaminated soil by providing the metabolite as the sole source of sulphur in broth culture. No microbial growth was observed in the absence of endosulphate. In the presence of endosulphate, growth of the culture occurred with the concomitant formation of three chlorine-containing compounds. Thin layer chromatography and gas chromatography±mass spectral analysis identi®ed these metabolites as endosulfan monoaldehyde, 1,2,3,4,7,7-hexachloro-5,6-bis(methylene)bicyclo[2.2.1]-2-heptene and 1,2,3,4,7,7-hexachloro-5-hydroxymethylene-6-methylenebicyclo[2.2.1]-2-heptene. The second and third compounds have not been reported in previous metabolic studies. The enriched culture was also able to utilize a-and b-endosulfan as sulphur sources, each producing the hydrolysis product endosulfan monoaldehyde as the sole chlorine-containing metabolite. Alpha-endosulfan was more readily hydrolysed than the b-isomer. Conclusions: This study isolated a mixed microbial culture capable of degrading endosulphate. The products of degradation were characterized as novel endosulfan metabolites. Signi®cance and Impact of the Study: This study describes the isolation of a mixed microbial culture that is potentially a valuable source of hydrolysing enzymes for use in enzymatic bioremediation, particularly of endosulphate and a-endosulfan residues.

A Single Monooxygenase, Ese, Is Involved in the Metabolism of the Organochlorides Endosulfan and Endosulfate in an Arthrobacter sp

“…Growth was not observed in sulfur-free medium alone. Concomitant with growth in the endosulfan-and endosulfate-supplemented medium there was a reduction in the abundance of these compounds and previously described metabolites appeared (28) (Fig. 1).…”

“…A bacterium (strain KW) capable of degrading ␣-endosulfan, ␤-endosulfan, and endosulfate was isolated from the mixed microbial culture of Sutherland et al (28), which was grown under continuous pressure to use endosulfate as the sole source of sulfur. Growth was indicated by an increase in the optical density at 595 nm of more than 0.35 over 4 days.…”

“…It is therefore important in the management of pest species. However, endosulfan is extremely toxic to fish and aquatic invertebrates, and this has led to an interest in postapplication detoxification of this insecticide (27)(28)(29)(30).Commercial endosulfan is a mixture of two diastereoisomers (approximately 30% ␤-endosulfan and 70% ␣-endosulfan) which differ dramatically in their physicochemical and environmental properties (31). The environmental dispersion pathways include hydrolysis of the sulfur moiety to nontoxic endosulfan diol or oxidation to endosulfate.…”

“…It is therefore important in the management of pest species. However, endosulfan is extremely toxic to fish and aquatic invertebrates, and this has led to an interest in postapplication detoxification of this insecticide (27)(28)(29)(30).…”

The enzymatic basis for pesticide bioremediation

“…Endosulfate is a toxic metabolite of both isomers that is more persistent than either parent isomer (α and β-endosulfan) [10,11]. Genes encoding the Ese and Esd enzymes were identifi ed in bacteria isolated from endosulfan-exposed soil upon enrichment in sulfur-defi cient media with endosulfan or endosulfate supplied as the sole source of sulfur, a technique that targeted the relatively reactive sulfur moiety [12,13].…”