Biodegradation of α- and β-endosulfan by soil bacteria |
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Authors: | Sarfraz Hussain Muhammad Arshad Muhammad Saleem Azeem Khalid |
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Institution: | (1) Institute of Soil & Environmental Sciences, University of Agriculture, Faisalabad, 38040, Pakistan |
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Abstract: | Extensive applications of persistent organochlorine pesticides like endosulfan on cotton have led to the contamination of
soil and water environments at several sites in Pakistan. Microbial degradation offers an effective approach to remove such
toxicants from the environment. This study reports the isolation of highly efficient endosulfan degrading bacterial strains
from soil. A total of 29 bacterial strains were isolated through enrichment technique from 15 specific sites using endosulfan
as sole sulfur source. The strains differed substantially in their potential to degrade endosulfan in vitro ranging from 40
to 93% of the spiked amount (100 mg l−1). During the initial 3 days of incubation, there was very little degradation but it got accelerated as the incubation period
proceeded. Biodegradation of endosulfan by these bacteria also resulted in substantial decrease in pH of the broth from 8.2
to 3.7 within 14 days of incubation. The utilization of endosulfan was accompanied by increased optical densities (OD595) of the broth ranging from 0.511 to 0.890. High performance liquid chromatography analyses revealed that endosulfan diol
and endosulfan ether were among the products of endosulfan metabolism by these bacterial strains while endosulfan sulfate,
a persistent and toxic metabolite of endosulfan, was not detected in any case. The presence of endosulfan diol and endosulfan
ether in the bacterial metabolites was further confirmed by GC-MS. Abiotic degradation contributed up to 21% of the spiked
amount. The three bacterial strains, Pseudomonas spinosa, P. aeruginosa, and Burkholderia cepacia, were the most efficient degraders of both α- and β-endosulfan as they consumed more than 90% of the spiked amount (100 mg l−1) in the broth within 14 days of incubation. Maximum biodegradation by these three selected efficient bacterial strains was
observed at an initial pH of 8.0 and at an incubation temperature of 30°C. The results of this study may imply that these
bacterial strains could be employed for bioremediation of endosulfan polluted soil and water environments. |
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Keywords: | Bacterial biodegradation Endosulfan pH Temperature |
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