In vitro toxicity evaluation of organic extract of landfill soil and its detoxification by indigenous pyrene-degrading Bacillus sp. ISTPY1

• Bacillus sp. strain ISTPY1 was evaluated for its degradation potential.
• The bacterium is capable of degrading pollutants in mixed carbon source.
• MTT, Comet and EROD bioassays significantly showed toxicity reduction.
• Bioassays are necessary for toxicity evaluation of environmental waste.

Organic contaminants present in okhla landfill soil belong to the group polyaromatic hydrocarbons, pharmaceutical compounds, steroidal compounds, personal care products and their derivatives. An indigenous pyrene-degrading Bacillus sp. ISTPY1 was used to treat the Okhla landfill soil. GC–MS analysis of the organic extract before and after biodegradation with Bacillus sp. ISTPY1 showed the elimination of various polyaromatic hydrocarbons and other persistent aromatic compounds. Toxicity study was done on human hepato-carcinoma cell line HepG2 before and after treatment. The bacterium treated sample initially showed reduction in toxicity till 48 h. This was increased after 120 h due to formation of quinones intermediate and further decreased after 360 h. The LC50 value (MTT assay) also showed the same pattern. The reduction in Olive Tail Moment was observed after 360 h treatment. Result of the study indicated biodegradation and detoxification of major contaminants of Okhla landfill by Bacillus sp. ISTPY1.