Bioremediation: An Eco-friendly Cleanup Strategy for Polyaromatic Hydrocarbons from Petroleum Industry Waste

The polycyclic aromatic hydrocarbons (PAHs) are a major pollutant from petroleum industry and oil refineries. This group of organic xenobiotics is produced either by pyrolytic or petrogenic sources. The physicochemical properties of PAHs such as hydrophobicity and electrochemical stability increase its persistence in the environment and add to the carcinogenicity and other health impacts. The major degradation processes of PAH in the environment are adsorption, volatilization, photolysis, chemical oxidation, bioaccumulation, and microbial degradation. The microbial communities like bacteria, fungi, and algae play a significantly important role in the biological removal of PAHs. The natural attenuation, bioaugmentation, biostimulation, phytoremediation, rhizoremediation, and composting are major bioremediation approaches for PAHs from contaminated environment. The enzymes linked with the PAH degradation are mainly oxygenases, manganese peroxidases, lipases, and laccases. The surfactant production in the microbes increases the bioavailability of PAH and enhanced the removal process. The PAH degradation depends on the various environmental conditions such as temperature, pH, aeration, moisture content, nutrient availability, absence of toxic compounds, and the type and number of degrading microbial population. The bacterial and fungal degradation pathways produce intermediate metabolites and mineralization to carbon dioxide. The molecular techniques like gene engineering and protein engineering improve the removal of PAHs. Thus the biodegradation of PAHs is linked to the carbon cycle and remediation of these persistent organo-molecules from the environment.