Biodegradation kinetics and metabolism of Benzo(a)fluorene by Pseudomonas strains isolated from refinery effluent

• Published in: Chemosphere (Oxford) 2022-11, Vol.307, p.136041-136041, Article 136041
• Main Authors: Goveas, Louella Concepta, Selvaraj, Raja, Kumar, P. Senthil, Vinayagam, Ramesh, Sajankila, Shyama Prasad
• Format: Article
• Language: English
• Subjects: Benzofluorene; Metabolic pathway; Persistent organic pollutants; Polycyclic aromatic hydrocarbons; Pseudomonas sp; Rate constant
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.136041

The final sinkers of polyaromatic hydrocarbons are water sources, where they undergo bioaccumulation and biomagnification, leading to adverse mutagenic, carcinogenic, and teratogenic effects on exposure in flora, fauna, and humans. Two indigenous strains, Pseudomonas sp. WDE11 and Pseudomonas sp. WD23, isolated from refinery effluent, degraded over 97.5% of benzo(a)fluorene (10 mg/L) in 7 days. On growth at concentration dependent amounts (50 mg/L and 100 mg/L), the degradation reduced to approximately 90% and 80% respectively in 56 days. Degradation kinetics was concentration dependent, as degradation followed first-order and second-order kinetics for 50 mg/L and 100 mg/L respectively. The half-life for degradation of benzo(a)fluorene ranged between 11.64 - 12.26 days and 13.11–14.5 days for strains WDE11 and WD23 respectively. The values of Andrew-Haldane kinetic parameters i.e. μmax, Ks, and Ki were 0.306 day−1, 11.11 mg/L, and 120.41 mg/L for strain WDE11 respectively, while for strain WD23, the respective values were 0.312 day−1, 9.97 mg/L, and 152 mg/L. Degradation metabolites were identified by their MS patterns as 3,4-dihydroxy fluorene, 2-(1-oxo-2,3-dihydro-1H-inden-2-yl) acetic acid, 3,4-dihydrocoumarin, salicylic acid, catechol, and oxalic acid. Metabolic pathway of degradation constructed, revealed that benzo(a)fluorene was metabolized via the formation of fluorene, further metabolized by salicylate pathway forming catechol. The catechol formed was degraded into simpler metabolites by meta-cleavage pathway, which was validated by catechol 2,3 dioxygenase enzyme activity. [Display omitted] •Indigenous Pseudomonas strains utilize benzo(a)fluorene as sole carbon source.•Degrade over 80% of 100 mg/L in 56 days.•Degradation kinetics is concentration dependent – first-order at lower concentration, second-order at higher.•Metabolic pathway of benzo(a)fluorene elucidated – metabolites of fluorene degradation identified.•Salicylate pathway followed by meta cleavage of catechol – first report.