Synergistic degradation of phenanthrene by constructed Pseudomonas spp. consortium compared with pure strains

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are highly persistent compounds as well as they have a toxic impact to all living organisms. Removal of these xenobiotic compounds by mixed bacteria is achieving a maximum degradation rate over the pure strains. So, this study substantiates the application of constructed bacterial consortium for degradation of 400 mg/L phenanthrene within 30 days of incubation at 30 °C. The consortium consisted of two bacterial species Pseudomonas pseudoalcaligenes (B1) and Pseudomonas aeruginosa (B2). It exhibited a significantly higher phenanthrene degradation efficiency (97.5%) compared to pure strains B1 and B2 (52.5 and 47.6%), respectively. The phenanthrene degradation rate by the individual strains was enhanced in the presence of salicylic and phthalic acids as intermediates pathway. On the other side, the degradation rate was reduced in the presence of catechol suggesting a feedback inhibition of catabolic enzymes. The ring-cleavage dioxygenases were induced in all treatments. However, the induction of ortho cleavage dioxygenase (2.44 U/mg protein) was higher than meta cleavage dioxygenase (0.42 U/mg protein). Six main metabolites were detected by GC–MS analysis. Among them, four metabolites were detected in the extract of phenanthrene growing consortium suggesting three main pathways, phthalate, salicylic and benzocoumarin by the constructed consortium. Therefore, this study provides a measuring of phenanthrene degradation efficacy by bacterial consortium and paved the way to increase the potential of using the consortium for successful removal of PAHs from the polluted environment.