Enhancing biodegradation of polycyclic aromatic hydrocarbons using bacterial consortia and biofilm

The release of petroleum and its constituents, such as polycyclic aromatic hydrocarbons (PAHs), into the environment poses a significant global threat due to their toxic, genotoxic, mutagenic, and/or carcinogenic properties. Using indigenous PAH-degrading bacteria to decontaminate the PAHs is an eco-friendly, convenient, and non-expensive way in comparison to other traditional physical and chemical methods. In the present study, several bacteria were isolated from petroleum-contaminated soils using a culture-enrichment technique. Phenanthrene and naphthalene were used as representative examples of the PAHs and as sole carbon and energy sources for the isolated bacteria. Three isolates (A1, A3, and B8-1) were selected as the most potent phenanthrene and naphthalene degraders. These three most potent isolates were used to build up four different consortiums, and both the individual isolates and developed consortiums were induced to set up biofilms. The results showed that the highest growth and degradation rate of phenanthrene and naphthalene were achieved at 37 °C and pH 7. Individual strains had higher phenanthrene degrading capacities compared to microbial consortiums in both planktonic and biofilm forms. Additionally, the developed-biofilm displays an increase in the degradation rate of individual isolates A1, A3, and consortiums. Finally, the selected biofilm degraders were used to investigate the PAHs degradation ability in an artificially contaminated soil. The finding of this experiment demonstrate that the biofilm mode of growth could be more effective in PAHs degradation compared to planktonic cultures, thus it can be applied effectively to remediate PAHs-contaminated soils. The most potent PAHs degraders were identified using 16 S rRNA, and the phylogenetic sequence analysis of the three isolates was affiliated as B8-1(Bacillus paramycoides), A1(Bacillus paranthracis), and A3(Bacillus licheniformis).