Elucidating the mechanisms of anthracene and phenanthrene degradation by the halophile Vreelandella piezotolerant DM1.

Polycyclic aromatic hydrocarbons (PAH) are prevalent environmental contaminants, which exhibit the mutagenic, carcinogenic, and teratogenic properties. The growing demand for efficient PAH biodegradation (BD), particularly in wastewater treatment. This research investigates hydrocarbon degradation using Vreelandella piezotolerant DM1 across a various pH levels (4, 6, 7, 8, and 10) and its enzymatic capabilities. The study assessed the degradation potential of anthracene and phenanthrene under varying PAH concentrations and pH conditions. Optimal bacterial growth and degradation were observed at 300 mg/L of both anthracene and phenanthrene at pH 8. To elucidate the degradation mechanisms, crucial intermediates were identified using gas chromatography mass-spectrometry (GC-MS). The hydrocarbon breakdown intermediates including anthracene-cis-1,2-dihydrodiol, (3Z)-4-[3-hydroxy(2-naphthyl)]-2-oxobut-3-enoic acid, 6,7-benzocoumarin, 1-hydroxy-2-naphthaldehyde, phenanthrene-cis-1,2-dihydrodiol, 1-hydroxy-2-naphthoic acid, and salicylic acid were observed during BD. Both intermediate compounds were conformed the salicylic acid pathway. GC-MS confirms the efficient degradation rates of 62% for anthracene, 82% for phenanthrene, and 83% for mixed hydrocarbons. These observations confirm that optimal conditions are obligatory for the enzymatic activity of the DM1 and a biodegradation pathway was proposed on the identified intermediates. In conculsion, V. piezotolerant DM1 serves as a potential candidate for hydrocarbon degradation in contaminated environment.