Evaluation Of Tolerance To Increasingly Higher Diesel Concentrations By Some Isolated And Characterized Indigenous Bacterial Species For Their Possible Utilization In Bioremediation Technologies

Abstract

Diesel, a hydrocarbon-based fuel essential for transportation and power generation, is a major environmental pollutant. Fortunately, bioremediation offers a sustainable solution, as certain bacteria can metabolize diesel components, converting them into less harmful byproducts while using them as an energy source. Thus, the aims of this study were to screen, select, and characterize local bacterial strains capable of decomposing diesel from petroleum contaminated soils and to test their tolerance for increasing diesel concentrations as potentials means for bioremediation in environmental cleanup. (20) samples of soil contaminated with petroleum derivatives from different areas of southern Babylon were taken and cultured on liquid basal  salt medium and   Bushnell has mineral salt agar . (9) samples were found to be positive (45%), while (11) samples were found to be negative (55%) for bacterial growth. 18 bacterial isolates were obtained, and  colonies with distinct phenotypes were selected  and identified using cultural, microscopic, and biochemical tests by the Vitek 2 compact system. Six different bacterial species were identified, namely Enterobacter cloacae complex, Escherichia hermannii ,Staphylococcus lentus ,Citrobacter sedlakii, Aeromonas salmonicida ,Sphingomonas paucimobilis . Their tolerance to increasingly higher diesel concentrations  was evaluated by  measuring optical density (OD600) in  liquid Bushnell has mineral salt  containing different concentrations of diesel ( 1%, 3%, 5%, and 10% )using a UV/Vis spectrophotometer after incubation period of 5, 10, and 15 days. The results showed that the growth rates for all the tested bacterial  species were higher in low diesel concentrations , while  a  notable decrease in growth  was indicated with higher diesel concentrations. Therefore, all of the selected strains may be putative species for bioremediation of diesel contaminated environments particularly with low concentrations.