Assessment of petroleum hydrocarbons biodegradation by indigenous Bacillus strains from Khyber Pakhtunkhwa, Pakistan.

The increased environmental pollution from petroleum hydrocarbons, chemicals, and heavy metals has grown more severe with rapid industrialization and population growth, highlighting the urgent need for effective biodegradation methods. This investigation assessed the capacity of bacterial strains, previously obtained from remote areas, Light sweet crude oil with a density of 0.83 g/cm3 (API gravity: 39.5°) was used at a concentration of 1 % (v/v), equivalent to 8.3 g/L through an enrichment culture method. The strains previously characterized through 16S rDNA sequencing and phylogenetic analysis were used in the study. The degradation efficiency was evaluated over 20 days through the evaluation of various parameters including pH, optical density, temperature, and carbon dioxide emission. SEM and GC-MS analysis techniques were conducted to investigate the structural and functional alterations in petroleum constituents. Three strains-Bacillus spp., Bacillus amyloliquefaciens, and Bacillus safensis-demonstrated notable degrading activity. Bacillus spp. exhibited the most rapid degradation (65 %) within five days, while Bacillus amyloliquefaiens displayed the degradation (50 %), and Bacillus safensis with the degradation ratio (78.33 %) exhibiting enhanced activity over 10-15 days. SEM analysis revealed morphological changes and biofilm development consistent with hydrocarbon degradation. GC-MS confirmed a reduction in hydrocarbon peak profiles. The findings underscore the strong biodegradation potential of indigenous Bacillus strains and their promise in the bioremediation of crude oil-contaminated environments.