Biodegradation of hexachlorocyclohexane-isomers in contaminated soils

• Published in: Soil biology & biochemistry Vol. 38; no. 8; pp. 2318 - 2327
• Main Authors: Kumar, Manish, Gupta, S.K., Garg, S.K., Kumar, Ashwani
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2006; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; biodegradation; Biological and medical sciences; Bioremediation; Chemical, physicochemical, biochemical and biological properties; Degradation; Detoxification; earthworms; Eisenia fetida; Fundamental and applied biological sciences. Psychology; HCH (pesticide); Hexachlorocyclohexane; Physics, chemistry, biochemistry and biology of agricultural and forest soils; polluted soils; Pseudomonas aeruginosa; Soil and water pollution; soil bacteria; soil chemical properties; soil pollution; Soil science; toxicity testing; India; Degradation; Pseudomonas aeruginosa; Hexachlorocyclohexane; Bioremediation; Detoxification; Pseudomonadales; Biodegradation; Insecticide; Pollution control; Pesticides; HCH; Soil pollution; Contamination; Isomer; Organochlorine compounds; Bacteria; Pseudomonadaceae; Soil science
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2006.02.010

Several sites that are contaminated with isomers of the chlorinated insecticide hexachlorocyclohexane (HCH) are present across the globe and cause toxicity. For their bioremediation, we studied the degradation of HCH-isomers in contaminated soils by an isolate Pseudomonas aeruginosa ITRC-5. The degradation is optimal at 2 mg technical-HCH ( t-HCH)/g soil, 15% water content, pH 8.0, temperature 28 °C and inoculum density 10 6 colony forming unit/g soil. Under these conditions, from 5 kg soil, >98% α- and γ-HCH, 17% β-HCH and 76% δ-HCH are degraded after 15 days of incubation, which is accompanied with the release of 600 μg chloride/mg t-HCH. Concomitant to the degradation, a four-fold reduction in the toxicity of HCH-isomers to earthworm, Eisenia foetida, is also observed. Addition of ITRC-5 enhanced the degradation of soil-applied HCH-isomers in ‘open field’ conditions as well, and 97%, 43%, 94% and 77% of α-, β-, γ- and δ-HCH, respectively, are degraded after 12 weeks of incubation. Thus, the bacterium causes microbial degradation and detoxification of HCH-isomers, and can be used for the bioremediation of contaminated soils.