Diversity of Native Hydrocarbon Degrading Bacterial Strains and Their Potential in Bioremediation of Soil Polluted by Crude Oil in Khuzestan Province (A response Surface Methodology Approach)

Many bioremediation strategies have been developed to help improve soil clearance from oil and its derivatives. The use of native bacteria to decompose crude oil-contaminated soils has been studied by many researchers. Along with this line of research, in the present study, a consortium of bacteria isolated from three different soil types in the Khuzestan region was used after identification. Finally, the optimal conditions for bioremediation of each soil type were determined. The results showed that the isolated strains were five unique strains, including Cupriavidus metal lidurans, Bacillus pacificus, Lysinibacillus fusiformis, Brevibacillus borstelensis, and Ralstonia metallidurans. These had good growth potential in contaminated soils and could effectively reduce TPH. Among the factors examined, the amount of moisture and nitrogen were two essential factors that reduce the amount of TPH. In optimal conditions, the moisture percentage was 135, 147, and 142, and the input nitrogen was 512 ppm, 513 ppm, and 617 ppm, for three types of soil, in Andimeshk, Ahvaz, and Abadan, respectively. NH4NO3, as the best source of nitrogen, had the best performance. In confirmatory experiments with 2.5% crude oil in optimal conditions, the rate of TPH reduction after 56 days was 48.4%, 53.4% and 56.4% for Abadan, Ahvaz, and Andimeshk soils, respectively. This study confirms the efficiency of native bacteria isolated from the soils of Khuzestan province for biodegradation of crude oil and introduces Bacillus pacificus bacteria as a new species that can bioremediation.