Optimization of conditions for polycyclic aromatic hydrocarbons (PAHs) degradation by Pseudomonas stutzeri P2 isolated from Chirimiri coal mines

•Bacterial degradation of PAHs in CFMM.•Involvement of dioxygenases in PAHs degradation.•Production of biosurfactant by Pseudomonas stutzeri P2.

A potent phenanthrene and pyrene degrading bacterial strain P2 was isolated from soil sample collected from the Chirimiri coal mines in central India. As determined through atomic absorption spectroscopy, a high concentration of heavy metal ions like lead, mercury and arsenic were found in the soil sample. The bacterial strain P2 was identified as Pseudomonas stutzeri through a polyphasic approach. The degradation conditions for phenanthrene and pyrene biodegradation was optimized through Taguchi orthogonal array. At optimized conditions, the strain could degrade 98% and 92.6% of phenanthrene and pyrene at a concentration of 1000 mg l−1 and 500 mg l−1 in 7 and 10 days, respectively. The pH of the medium dropped during degradation studies suggesting the accumulation of acidic metabolites during biodegradation by the isolated strain. The gas chromatography-mass spectrometry analysis of phenanthrene and pyrene degradation products showed the presence of pthalic acid derivatives. PCR amplification of dioxygenase genes produced fragments of 350 bp, 867 bp and 350 bp in length for PAH-RHD, catechol 2, 3-dioxygenase and catechol 1, 2-dioxygenase, respectively suggesting the representative of Pseudomonas as the significant PAHs degrader. The bacterial strain was found to be biosurfactant producing, and the role of biosurfactant in PAHs degradation was also determined by higher emulsification index and reduced surface tension of the medium. Significantly, the Pseudomonas strain could tolerate heavy metals and utilize a range of mono and polyaromatic as the sole source of carbon. Hence, this strain has a remarkable potential for application in bioremediation of hydrocarbon contaminated sites.

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