Marine Bacterial Biofilms in Bioremediation of Polycyclic Aromatic Hydrocarbons (PAHs) Under Terrestrial Condition in a Soil Microcosm

Abstract

Polycyclic aromatic hydrocarbons (PAHs) in soil retain for a quite long period due to their hydrophobicity and aggregation properties. Biofilm-forming marine bacterial consortium (named as NCPR), composed of Stenotrophomonas acidaminiphila NCW702, Alcaligenes faecalis NCW402, Pseudomonas mendocina NR802, Pseudomonas aeruginosa N6P6, and Pseudomonas pseudoalcaligenes NP103, was used for the bioremediation of PAHs in a soil microcosm. Phenanthrene and pyrene were used as reference PAHs. Parameters that can affect PAH degradation, such as chemotaxis, solubility of PAHs in extracellular polymeric substances (EPS), and catechol 2,3-dioxygenase (C23O) activity, were evaluated. P. aeruginosa N6P6 and P. pseudoalcaligenes NP103 showed chemotactic movement towards both the reference PAHs. The solubility of both the PAHs was increased with an increase in EPS concentration (extracted from all the 5 selected isolates). Significantly (P < 0.001) high phenanthrene (70.29%) and pyrene (55.54%) degradation was observed in the bioaugmented soil microcosm. The C23O enzyme activity was significantly (P < 0.05) higher in the bioaugmented soil microcosm with phenanthrene added at 173.26 ± 2.06 nmol min−1 mg−1 protein than with pyrene added at 61.80 ± 2.20 nmol min−1 mg−1 protein. The C23O activity and gas chromatography-mass spectrometer analyses indicated catechol pathway of phenanthrene metabolism. However, the metabolites obtained from the soil microcosm added with pyrene revealed both the catechol and phthalate pathways for pyrene degradation.