Characterization of Halophilic Bacteria Vreelandella piezotolerant DM1 on Biodegradation of Polyaromatic Hydrocarbons and its Pathway

Polycyclic aromatic hydrocarbons (PAHs) with high molecular weights are significant marine pollutants. This study aimed to determine the ability to degrade PAHs (pyrene and benzo[a]pyrene) by Vreelandella piezotolerant DM1 under halophilic conditions. Biodegradation of PAHs was performed in isolate DM1, and the experiment was incubated at 37 °C for 15 days in a hypersaline environment. A bacterial consortium effectively degrades PAHs by secreting alkane hydroxylase (AH) and alcohol dehydrogenase (AD) as key enzymes. At 250 mg/L PAH, the removal efficiencies of TOC and COD were 67–75% and 69–78%, respectively. DM1 was well adapted to saline conditions and effectively metabolised (PAHs). Fourier-transform infrared spectroscopy (FT-IR) confirmed the utilisation of various types of functional groups present in PAHs. Gas chromatography-mass spectroscopy (GC–MS) confirmed that the bacterial strain effectively degraded pyrene (58%) and benzo[a]pyrene (70%) and mixed at 88% within 15 days. The intermediate metabolites, phenanthrene-4,5-dicarboxylic acid, 3,4-dihydroxy phenanthrene, 1-(2-hydroxyphenyl)2-phenylethanone, and phthalic acid, were identified. Based on these metabolites, a possible PAH biodegradation pathway was proposed. Overall, this study elucidated the role of halophilic bacteria in the biodegradation of PAHs and their degradation pathways and found that the strain was suitable for the biodegradation of PAHs in a hypersaline environment.