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

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 identified these metabolites as endosulfan monoaldehyde, 1,2,3,4,7,7-hexachloro-5,6-bis(methylene)bicyclo2.2.1]-2-heptene and 1,2,3,4,7,7-hexachloro-5-hydroxymethylene-6-methylenebicyclo2.2.1]-2-heptene. The second and third compounds have not been reported in previous metabolic studies. The enriched culture was also able to utilize alpha- and beta-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 beta-isomer. CONCLUSIONS: This study isolated a mixed microbial culture capable of degrading endosulphate. The products of degradation were characterized as novel endosulfan metabolites. SIGNIFICANCE 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 alpha-endosulfan residues.