Isolation and Identification of Phenanthrene-Degrading Bacteria from Crude Oil-Contaminated Soils around Assaluyeh Refinery: Growth Evaluation and HPLC-Based Degradation Analysis

Polycyclic Aromatic Hydrocarbons (PAHs) are toxic organic compounds that pose significant environmental contamination risks. This study aimed to screen and molecularly identifies bacteria capable of degrading phenanthrene, a representative PAH, from petroleum-contaminated soils. Samples were collected from the Arak and Bushehr oil refineries for bacterial isolation. Initial identification was based on morphological and biochemical characteristics. Ten bacterial strains were assessed for their growth on phenanthrene as the sole carbon source. The most efficient strains were further identified through 16S rRNA gene sequencing. Growth dynamics in mineral media containing phenanthrene were monitored using a spectrophotometer, while residual phenanthrene levels were quantified via High-Performance Liquid Chromatography (HPLC). The results revealed that Bacillus thuringiensis, Aeromonas caviae, and Salmonella enterica exhibited phenanthrene degradation efficiencies of 55.82%, 51.1%, and 44.7%, respectively, after 72 hours. These bacteria demonstrated both resistance to and utilization of phenanthrene as a carbon and energy source, underscoring their potential for bioremediation applications at the pilot scale.