Benzene degradation with bacterial strains isolated from rhizosphere of Cannabis sativa being irrigated with petroleum refinery wastewater

Abstract

Rhizoremediation is considered as an environmentally friendly technique to deal with the contamination of petroleum hydrocarbons. The current study was aimed at checking the potential of indigenous micro-organisms isolated from rhizosphere soil being irrigated by the wastewater of petroleum refinery to degrade benzene efficiently. For this study, soil samples were taken from the discharge point of oil refinery located in Rawalpindi, Pakistan, by brushing off the soil from roots of Cannabis sativa. The soil was processed for isolation of indigenous microbial strains. Sixteen bacterial strains isolated from the soil were screened for their potential to grow using benzene as sole carbon source in vitro. These were exposed initially to 250 mg L⁻¹ followed by 500 and 750 mg L⁻¹ of benzene, where only seven strains were able to survive with optical density (OD₆₀₀) of ≥1.1. Three better performing strains with OD₆₀₀ > 1.6 were further subjected to degrade 1,000 mg L⁻¹ benzene (sole carbon source) using M9 media. The community diversity analysis for the best performing strains was carried out using 16S ribosomal RNA. Pseudomonas aeruginosa (SAR-1) was the best degrader with 85% benzene degradation in 72 hours followed by Bacillus cereus (SAR-2) and Acinetobacter junii (SAR-3) with 83 and 70% efficiency, respectively. To the best of our knowledge, A. junii (SAR-3) is being reported as a benzene degrader for the first time.

Keywords:

• Rhizoremediation
• Benzene
• Refinery wastewater
• Pseudomonas aeruginosa
• Bacillus cereus
• Acinetobacter junii

Acknowledgments

The authors would like to thank S&T Mega Fund, National University of Sciences and Technology (NUST), Islamabad, Pakistan for financial support. We are also thankful to Prof. Imran Hashmi and Dr Faraz Bhatti, NUST, Islamabad for their kind guidance and help during the study and to Ms Aisha Chaudhry, Walden University, Baltimore, USA for English revisions.