Biodegradation of mixed polycyclic aromatic hydrocarbons by newly isolated Priestia megaterium KS01 and its enzymatic pathway profiling

Polycyclic aromatic hydrocarbons (PAHs) are environmentally persistent contaminants of concern due to their toxicity, mutagenicity, and resistance to natural attenuation. Biodegradation by specialized microorganisms represents an effective strategy for their removal from contaminated environments. In this study, a novel bacterial strain, Priestia megaterium KS01, was isolated from oil sand tailings, demonstrating significant potential for PAHs biodegradation. Hydrocarbon degradation efficiency decreased with increasing chain length (C 9 -C 12 ) and diesel concentrations (3%, 5%, and 10% v/v), consistent with reduced bioavailability and substrate inhibition. GC-MS profiling of representative PAHs showed distinct compound-specific behaviors. Approximately 40% methylated naphthalenes were removed efficiently at low diesel concentrations of 3% (v/v) but were strongly inhibited at higher loads (5% and 10% v/v). In contrast, acenaphthylene, acenaphthene, and fluorene exhibited enhanced degradation at elevated diesel concentrations of 10% (v/v), suggesting co-metabolic stimulation. Proteomic analysis identified key enzymes, including cytochrome P450, α/β-hydrolase fold proteins, and ring-cleaving dioxygenases, supporting the presence of dual monooxygenase- and dioxygenase-mediated pathways. Together, these results highlight the metabolic versatility of P. megaterium KS01 and its strong potential as a candidate for the bioremediation of PAH-contaminated environments. • Priestia megaterium KS01, isolated from oil sand tailings, efficiently degrades polycyclic aromatic hydrocarbons (PAHs). • Degradation decreased with higher chain length (C 9 –C 12 ) and diesel load (3–10% v/v). • Methylated naphthalenes degraded by nearly 40% at 3% (v/v) diesel in 15 days. • Acenaphthylene, acenaphthene, and fluorene showed co-metabolic stimulation at 10% (v/v) diesel. • Enzymatic analysis revealed dual monooxygenase- and dioxygenase-mediated PAH