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Impact of the Composition of the Bacterial Population and Additional Carbon Source on Pathway and Kinetics of Degradation of Endosulfan Isomers

Abstract

Abiotic and bacterial degradation is presented for the two isomers α- and β- of the organochlorine pesticide endosulfan, denoted as ES-1 and ES-2, respectively. Biodegradation studies were conducted with two indigenous species Pseudomonas Putida (P. putida) and Rhodococcus sp. Both the ES isomers rapidly hydrolyzed in water at pH ≥7 but the hydrolysis was inhibited in the presence of biomass. The pesticide partitioned onto the biomass making it unavailable for abiotic hydrolytic reaction. Spontaneous temperature dependent abiotic conversion of ES-2 to ES-1 was reported in the presence of dual air-water phases but was not observed in the abiotic aqueous phase. Biodegradation experiments with pure isomers showed a small amount of interconversion (~5%) in either direction and ruled out any preferential interconversion of the ES-2 isomer to ES-1 or vice-versa. Both the species were shown to degrade ES-2 at a higher rate compared to ES-1 which may lead to enrichment of ES-1 in an agricultural field in the short-term following application of the pesticide. P. putida degraded both the ES isomers through oxidative and hydrolytic pathways while the Rhodococcus sp. used only the hydrolytic pathway. Since ES-S (product of the oxidative pathway) is orders of magnitude more toxic than the parent isomers, the short term toxicity of a field following the application of the pesticide may increase if the composition of the indigenous bacterial population is such that the oxidative pathway is preferred over the hydrolytic one. Presence of additional carbon source increased the rates of degradation of both the isomers but enhancement was more for the degradation rate of ES-2 than ES-1.

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Publication details

The article was received on 29 Mar 2017, accepted on 11 Jun 2017 and first published on 13 Jun 2017


Article type: Paper
DOI: 10.1039/C7EM00154A
Citation: Environ. Sci.: Processes Impacts, 2017, Accepted Manuscript
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    Impact of the Composition of the Bacterial Population and Additional Carbon Source on Pathway and Kinetics of Degradation of Endosulfan Isomers

    S. P. Singh, P. Bose and S. Guha, Environ. Sci.: Processes Impacts, 2017, Accepted Manuscript , DOI: 10.1039/C7EM00154A

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