Biodegradation of fipronil by Paracoccus sp. in different types of soil.

In the present studies potential of microorganisms isolated from the cotton fields was explored for the bioremediation of fipronil contaminated soils. The cultures of microbes were grown in Luria broth as shake culture maintained at 28°C. After that Dorn's broth enrichment culture supplemented with fipronil was used and isolated two bacterial cultures viz. Paracoccus sp. and Gamma Proteobacteria. The performance of both bacteria was evaluated for degradation of fipronil in soil. Paracoccus sp. was found better than the Gamma Proteobacteria as far as degradation of fipronil in soil is concerned. The samples of soil were extracted and cleaned up by following a standardized methodology. Fipronil was quantified by gas liquid chromatography and confirmed by gas chromatography mass spectrometer. The limit of quantification of fipronil was worked out to be 10 μg kg(-1). By using this methodology, the mean recoveries of fipronil in different types of soil were found to be more than 85%. The residues of fipronil were found to persist only up to 10 days in soils fortified with fipronil @ 20 μg kg(-1) and amended with Paracoccus sp. while in the soils fortified @ 80 μg kg(-1) fipronil, residues persisted up to 20, 30 and 30 days in loamy sand, sandy loam and clay loam, respectively. Therefore, the use of Paracoccus sp. can further be explored for the bioremediation of fipronil contaminated soils.