Performance evaluation and mechanism analysis of halotolerant bacterial strains and cerium oxide nanoparticle to degrade Benzo[a]pyrene

Abstract

The key source for Benzo[a]pyrene (B[a]P) and various other Polyaromatic hydrocarbon (PAH) is partial ignition of crude oil, and several other by-products of petroleum and its components. Moreover, industries that utilises coal and further when coal is burnt during various natural and anthropogenic activities also leads B[a]P to cause great threat to the environment by getting mixed in the air. The PAH compounds are highly enduring, bio-toxic, cytotoxic, and cancerous. The aqua-phobic property of these hydrocarbons makes these stable and unreactive. Among various other environments marine environment is under great threat due to various anthropogenic activities like an oil leak accidents and industrial emission, specifically from factories. Due to the rapidly varying industrial trends the harmful pollutants get released into the saline and hypersaline environment. Thus, it is the need of the hour to find a way to degrade these toxic chemicals in the environment. Many physicochemical techniques to remediate B[a]P include chemical oxidation, photo-dissociation, burning, landfilling, volatilisation, and adsorption. The by-products from all the techniques cause severe harm to the environment. Here we describe the Benzo[a]pyrene degradation by employing two techniques, first through biodegradation and second using cerium oxide nanoparticles synthesised employing sol gel method. This current work aims to compare the degradation of B[a]P using both bacterial cocultures (Biological) and CeO2 nanoparticle (Chemical method). Mechanism of Biodegradation of B[a]P is proposed to take place by the hydroxylation through oxidation of aromatic ring, tracked by cis-dihydrodiol intermediates formation, finally resulting in cleavage to simple alcohols, carbonyl compounds, phenolics and carboxylic acids. The interpretation of the Mass spectrum also revealed some non-reported low molecular weight compounds like cyclopentadienyl, cyclobutadienyl cations, diacetylene and DHP, along with O-Cresol, Benzaldehyde, Benzoic acid, Naphthalene, Naphthol, Diacetylene and Dihydropyran. On comparing with biodegradation, the degradation using cerium oxide nanoparticles gave many simple, and fewer toxic by-products. • Halotolerant B[a]P degrading bacterial strains were isolated from marine environment. • Strains were screened and optimised for enhanced degradation of B[a]P. • Synthesis (citrate–nitrate sol–gel route) & characterisation of CeO 2 nanoparticles. • Degradation of benzo[a]pyrene of CeO 2 NP in the visible light. • Comparative study on bio and CeO 2 nanoparticle B[a]P degradation.