Biological treatment of PAHs using genetically modified local bacterial isolates

Abstract

Abstract Bioremediation technology by microorganisms, which already presents in the contaminated soils, is considered one of the primary mechanisms by which petroleum and other hydrocarbon pollutants can be removed from the environment. Twelve decomposing bacterial isolates were isolated from three polluted sites (Al-Dora oil refinery, Middle Refineries Company from oil wells, and Karbala oil refinery). This study showed high efficacy polycyclic aromatic hydrocarbons (PAHs) of isolated bacteria appropriate to polycyclic aromatic hydrocarbons decomposition. Primary and secondary screening of bacterial isolates has been performed using experiments based on the colour change in the medium resulting from the degradation of hydrocarbons in the nutrient medium. The screening results were three isolates that were characterized according to the basis of morphological and biochemical features and verified by Vitek 2, Pseudomonas aeruginosa, Escherichia coli and Sphingomonas paucimobilis. The mutagenesis process has been carried out by UV irradiation with a wavelength of 254 nm on selected bacterial strains. Experiments have been conducted on PAHs (naphthalene, phenanthrene and acenaphthene. According to the Biodegradation Efficiency result for 28 days, the best phenanthrene degrading bacteria was (Pseudomonas aeruginosa wild type (73.4%), Escherichia coli wild type (71.5%) and Sphingomonas paucimobilis wild type (68.8%). For naphthalin metabolism, the best degradation efficiency was (Pseudomonas aeruginosa wild type (86.2%), Sphingomonas paucimobilis wild type (69%) and Escherichia coli wild type (63%). At the same time, acenaphethene great degradation efficiency was Sphingomonas paucimobilis wild type (72%), Pseudomonas aeruginosa wild type (71%) and Sphingomonas paucimobilis mutant type (66%). We conclude that random mutation’s effect did not increase the degradation ability for most bacterial isolate.