Biodegradation of BTEX by Bacteria Isolated From Soil Contaminated With Petroleum Sludge and Liquid and Solid Petrochemical Effluents

BTEX is a significant pollutant of soil and water. This study aimed to isolate BTEX-decomposing bacteria from oil sludge-contaminated soil in the Bahregan area, as well as from liquid and solid petrochemical effluents in Lordegan. The research further investigated the extent of BTEX decomposition by the selected bacteria. The isolated bacteria were screened for their ability to grow and tolerate BTEX, leading to the selection of three strains (G2, M2, and K). The selected bacteria were then exposed to BTEX, and their degradation efficiency was evaluated. For the initial evaluation, residual BTEX was extracted using dichloromethane as the solvent, and the optical density at 600 nm (OD₆₀₀) of the separated organic phase was measured. Subsequently, gas chromatography (GC) analysis was performed for a more accurate assessment. The results from both tests indicated that the highest level of BTEX biodegradation by the tested isolates followed this order: G2(Arthrobacter pascens) > M2 (Bacillus sp.) > K. The biodegradation rate of each BTEX compound varied by isolate: G2 bacteria: T > B > X > E, M2 bacteria: B > T > X > E, K bacteria: E > X > T > B. Finally, the top-performing isolates were identified through gene sequencing. The G2 bacteria showed 98.36% similarity to Arthrobacter pascens B46W, while the M2 bacteria had 99% similarity to Bacillus sp. strain jrb-12w.