Bioremediation by bacteria isolated from water contaminated with hydrocarbons

Abstract

Oil pollution is currently a global problem. However, an oil-contaminated ecology is rich in microorganisms that may utilize petroleum oil and hydrocarbons for growth, feeding, and metabolic processes. In the present study, fifty polluted water samples were collected from five stations (ten samples each) in the Al-Fahama oil refinery in eastern Baghdad. The water contamination parameters of these collected water samples were detected. Then, the percentage of water contamination with some heavy metals (zinc, lead, and cadmium) and radioactive elements (uranium, cesium and actinium) was measured. The proportions of these elements were compared within their limits permitted by the World Health Organization (WHO). Fifty-nine bacterial isolates were isolated from polluted water, and 24 isolates of them succeeded in analyzing crude oil. The results of the current study showed that seven isolates belong to the genus Citrobacter amalonaticus (29.16%), six isolates belong to Enterobacter cloacae (25%), three isolates belonged to both Pseudomonas aeruginosa (12.5%) and Ochrobacterum anthropi (12.5%), and human Ochrobacterum. With a percentage of 12.5%, two isolates of Serratia marcescens (8.3%) and one isolate of each Pseudomonas fluorescens, Serratia fonticola, and Burkholderia pseudomallei (4.16%) of each. The optimum of some conditions for the decomposition process was determined in terms of (pH, temperature and crude oil concentration) and the results showed that the optimum degradation conditions were 35°C at pH equal to 7.5 in the presence of 2% of crude oil. Several experiments were conducted to determine the most efficient isolates for oil analysis. Burkholderia pseudomallei and Pseudomonas fluorescens are the most active bacterial species in their oil degradation. Genes responsible for hydrocarbon analysis were revealed in twenty-four bacterial isolates using a polymerase chain reaction (PCR) assay. The results showed that the ALKB gene (alkane hydroxylase) was observed in all bacterial isolates that succeeded in analyzing crude oil with a percentage equal to 100%, NahAc gene (naphthalene dioxygenase) has been recorded in four isolates (16.7%), these four bacterial isolates were Burkholderia pseudomallei, Pseudomonas aeruginosa, Ochrobacterum anthropic, and Pseudomonas fluorescens. Generally, the isolation rate of both C. amalonaticus and E. cloacae isolates was higher than in other studies, which may be due to the hydrocarbon pollution in isolation; both B. pseudomallei and P. fluorescens isolates were the highest active bacterial species in their oil degradation. Genetic results showed that the AlkB gene was the domain compared with other degradation genes used in the current study, followed by NahAc gene. Keywords: Bioremediation, heavy metal, B. pseudomallei, hydrocarbons, crude oil