Isolation and Identification of Bacillus Species from Soils Contaminated with Petroleum Derivatives and Detection of Their Role in the Biodegradation of Kerosene

The current study aimed to determine the biodegradation rate of crude oil using some different Bacillus species isolated from soil. 100 mg of contaminated and uncontaminated soil samples used in bioremediation experiments were collected from three areas in Tikrit city, including generator soil, refinery soil, and normal uncontaminated soil. The soil samples (weight: 100 g and depth: 3-12 cm) were collected using dark counters and then transferred to the laboratory. Hydrocarbon materials were added with the prepared nutrient agar medium and left to solidify, then both contaminated and normal soils were placed and incubated for 24 hours at 37 °C. the result showed that 86.7% of the bacterial isolates gave positive growth after being cultivated on blood and MacConkey agar media. While 13.3% of the soil samples showed negative bacterial growth when grown on the same media. the result showed that the most isolated bacteria was B. subtilis, which represented 28.6%, followed by B. tropicus, which represented 19.0%, while the lowest isolation percentage was for Bacillus taxi and B. flexus, which represented 4.8% of the total 21 isolates. The high degradation percentage by B. thuringiensis was 75% for a concentration of 1% kerosene. The high degradation percentage by B. subtilis was 82% for a concentration of 1% kerosene. The high degradation percentage by B. firmus was 69% for a concentration of 1% kerosene. The high degradation percentage was 83% for a concentration of 1% Kerosene. The high degradation percentage by B. taxi reached 73% for a concentration of 1% of kerosene. The high degradation percentage by B. muralis reached 93% for a concentration of 1% kerosene. The high degradation percentage by B. megaterium was 72% for a concentration of 1% kerosene. The results of the current study showed the ability of the studied Bacillus to biodegrade contaminated kerosene in soil. The most efficient Bacillus species in biodegrading kerosene was Bacillus muralis.