Isolation and investigation of bioremediation potentials of petroleum- degrading bacteria from Kurdistan region in Iraq

In our daily life and in industry, petroleum hydrocarbons are important as primary energy resources. Crude oil is used as raw matter in numerous industries, including the refinery-petrochemical industry, where crude oil is refined through different technological processes into usable products. Most of the petroleum goes in the ecosystem via leaks and accidental spills of coastal oil refineries. As a result, it directly or indirectly affects human safety and ecological systems. Toxic organic materials in crude oil can be carcinogenic, mutagenic and potent immunotoxicants and discharged into the soil and groundwater. One of these toxic materials is aliphatic hydrocarbons, particularly alkanes of shorter chain length (C10-C20) are more toxic. The aims of this study are to isolate and identify the bacterial strains from petroleum contaminated sites as well as determine the ability for the biodegradation of crude oil. For screening of hydrocarbon degrading microorganisms, different bacterial strains were isolated from different petroleum areas of Iraqi Kurdistan. The final isolates selected as the superiors hydrocarbon degraders were identified by morphological, physiological, biochemical screening tests and 16SrRNA sequence analysis. According to 16S rRNA gene sequencing analysis, five strains designated as 2B, 3B, 4A, 6C and 8F were found to be closely related to Cronobacter malonaticus (96.31% similarity), Cronobacter dublinesis subsp. dublinesis (95.48% similarity), Serratia marcescens subsp. marcescens (92.94% similarity), Pseudomonas aeruginosa (96.23% similarity) and Acinetobacter calcoaceticus (99.08% similarity) respectively. GC-MS analysis of hydrocarbons with chain length (C9- C34) showed that 2B, 4A, 6C and 8F were able to degrade 84.76%, 73.25%, 91.62%, and 41% n-alkanes, respectively, in the crude oil incubated for 10 days. Along with the selected individual strains, a mixed bacterial consortium prepared using the above strains were also used for degradation studies. The mixed bacterial consortium did not lead to enough growth and degradation. The mixed bacterial consortium degraded 69.50% percentage of n-alkanes ranging from C11 to C34.