Biotransformation Studies on Organochlorine Insecticide, Endosulfan by Indigenous Bacterial Isolate

M Supreeth,N S Raju

doi:10.12944/cwe.12.2.20

Abstract

Aerial application of persistent, bioaccumulative organochlorine pesticide endosulfan on cashew plantations to protect it from mosquito bug has led to contamination of soil and water environments in several parts of South Canara region, India. Endosulfan and its toxic residues like endosulfan sulfate are posing several threats to non-target organisms including humans. Biotransformation of toxic compounds using indigenous microbial strains is considered as safe and cost effective technique in bioremediation. In the present work, the bacterial strain designated as ES-1, has been isolated from the soil by enrichment method. The bacterial strain was found to mineralize endosulfan ˃99% of 100 mg/l completely biotically after 14 days of incubation by forming unknown polar metabolites.Whereas, abiotic degradation resulted in formation of a toxic compound, endosulfan sulfate. Based on 16s rDNA sequence analysis, the strain ES-1 showed 99% similarity to Bacillus sp. The results from the work suggest that, this bacterial strain could be employed for remediation of endosulfan contaminated environments.

Highlights

Pesticides used to protect crops have led to increased crop yield in the modern world
Earlier studies have shown the presence of Endosulfan isomers and endosulfan sulfate in various agricultural soils, water and other environmental samples in India and around the world.[9,10,11,12,13]. These findings show the contamination of various environmental samples with endosulfan and its metabolites along with other pesticides
Isolation of Endosulfan Degrading Bacterial Isolate The soil enrichment method adopted for isolating microbial culture resulted in isolation of bacterial strain which could tolerate high concentration of endosulfan

Summary

Introduction

Pesticides used to protect crops have led to increased crop yield in the modern world. Persistent Organochlorine Pesticide (OCPs) has been applied continuously in the last century to improve the agricultural productivity These OCPs being persistent organic pollutants and their metabolites are still present in the environments which are having mutagenic and carcinogenic effects.[1] Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9ahexahydro-6,9-methano-2,4,3-benzodio-3-oxide) is first generation Organochlorine pesticide introduced in 1950’s and approved for use in 1954 in USA. It exists in two isomers as a-Endosulfan or Endosulfan (I) and b-Endosulfan or Endosulfan (II) in the ratio 7:3 having almost similar insecticidal activities, but have significant differences with respect to Supreeth & Raju, Curr.

Methods

Results

Conclusion