Abstract
The current investigation is taken up with the aim of studying repeated batch and continuous degradation of Endosulfan, using Ca-alginate immobilized cells of Pseudomonas aeruginosa isolated from an agricultural soil. The work involves the study of genes and enzymes involved in the degradation of the pesticide and was carried out with an objective of reducing the toxicity of Endosulfan by degrading it to less toxic metabolites. The long-term stability of Endosulfan degradation was studied during its repeated batch degradation, carried out over a period of 35 days. Immobilized cells of Ps. aeruginosa were able to show 60 % degradation of Endosulfan at the end of the 35th cycle with a cell leakage of 642 × 104 Cfu/mL. During continuous treatment, with 2 % concentration of Endosulfan, 100 % degradation was recorded up to 100 mL/h flow rate and with 10 % concentration of the Endosulfan, and 100 and 85 % degradation was recorded at 20 mL/h flow rate and 100 mL/h flow rate, respectively. After degradation of Endosulfan, products were extracted from a large amount of spent medium using two volumes of ethyl acetate and subjected to the LC–MS analysis. Endosulfan lactone and Endosulfan ether were the products of degradation detected by the LCMS analysis. Plasmid curing experiments indicated that genes responsible for the degradation of Endosulfan are present on the chromosome and not on the plasmid, as growth of Ps. aeruginosa was observed on modified non-sulfur medium with Endosulfan after the plasmid was cured with ethidium bromide. The results of PCR indicated that there is no amplified product of ~1350 bp expected for esd gene, in Ps. aeruginosa, although there were some non-specific bands. Enzymatic degradation studies indicated that the enzymes involved in the degradation of Endosulfan are intracellular. With this investigation, it was indicated that immobilized cells of Ps. aeruginosa have the potential to be used in the bioremediation of water contaminated with Endosulfan.
Highlights
IntroductionIt is a mixture of the two isomers, a and b-Endosulfan
Plasmid curing experiments indicated that genes responsible for the degradation of Endosulfan are present on the chromosome and not on the plasmid, as growth of Ps. aeruginosa was observed on modified non-sulfur medium with Endosulfan after the plasmid was cured with ethidium bromide
Other chemicals used in the preparation of modified non-sulfur medium (Siddique et al 2003), K2HPO4, KH2PO4, NH4Cl, MgCl2Á6H2O, CaCO3, FeCl24H2O, and trace element solution, the preparation of phosphate buffer, chemicals used for the immobilization and estimation of Endosulfan, and the solvent Ethyl acetate and methanol used in the extraction and dissolution of endosulfan were of analytical grade
Summary
It is a mixture of the two isomers, a and b-Endosulfan. Both of these isomers are toxic, with the a-isomer being more toxic than b-isomer (JenNi et al 2005). It is used extensively throughout the world as a contact and stomach insecticide and as an acaricide on field crops, such as cotton, paddy, sorghum, oilseeds, coffee, vegetables, and fruit crops (Lee et al 1995; Kullman and Matsumura 1996). Endosulfan has been implicated in mammalian gonadal toxicity (Sinha et al 1997), genotoxicity (Chaudhuri et al 1999), and neurotoxicity (Paul and Balasubramaniam 1997)
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