A newly isolated Pseudomonas sp. can degrade endosulfan via hydrolytic pathway

Endosulfan an organochlorinated pesticide was used extensively throughout the world. Its enormous and inadequate use creates environmental as well as health problems. A bacterial strain capable to utilize endosulfan as a sole source of sulfur was isolated from pesticide contaminated soil and identified as Pseudomonas sp. on the basis of 16S rRNA. Batch experiments were conducted at various initial concentrations of endosulfan, i.e. 5, 25, 50, 75 and 100 mg/l to study its rate of degradation. After three days of incubation, 70-80% of each initial concentration was degraded by the isolated strain as compared to the control. Degradation of endosulfan increased with the time of incubation and maximum degradation was observed after 5 days of incubation. GC-MS revealed that the major metabolite was endosulfan lactone, which accumulated after 5 days of incubation. Kinetic studies at various initial concentrations also revealed that the bacterium has very promising attitude to utilize endosulfan as sole source of sulfur. It was observed that the addition of auxiliary sulfur Fe(SO₄)₃ in any concentration (0.05, 0.01 and 0.1%) decreased the rate of degradation of endosulfan. The ratio of μ_max/ K_s was high (0.03 mg/l) when endosulfan was single sulfur source as compared to the value recorded when Fe(SO₄)₃ was added alongwith the endosulfan. This indicates that the newly isolated bacterium attacks sulfur moiety for its degradation.