Biodegradation of cypermethrin by Bacillus sp. in soil microcosm and in-vitro toxicity evaluation on human cell line

Soil microcosms were set up with cypermethrin (100 mg/kg of dry soil) to assess the biodegradation by Bacillus sp. strain ISTDS2. Soil samples from the microcosms were collected at regular intervals during the biodegradation of cypermethrin and metabolites were extracted with hexane/Acetone (1:1v/v). GC–MS analysis of the soil extract showed formation of degraded compounds like cyclopropane, carboxylic acid, hydroxyacetonitrile and benzene ethanamine. The toxic effects of degraded product were studied on a human hepatocarcinoma cell line HuH7 before and after bacterial treatment. Methyltetrazolium (MTT) assay for cytotoxicity and alkaline comet assay for genotoxicity were carried for toxicity evaluation. The bacterium reduced toxicity as shown by a 105-fold increase in LC50 value, and a 3-fold reduction in Olive Tail Moment after 30 days of treatment. Biodegradation ability of the strain without toxic by-products reveals its potential for further study as a biological agent for the remediation of soil contaminated with cypermethrin.

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► Bacillus sp. was evaluated for its biodegradation and detoxification potential.
► The bacterium was capable of degrading cypermethrin, a potent genotoxic pesticide.
► Degradation pathway of cypermethrin in soil was obtained on basis of GC–MS data.
► Toxicity reduction was shown by MTT and Comet bioassays on human cell line.