Biodegradation of polycyclic aromatic hydrocarbons and the impact of various genes for their enhanced degradation

Polycyclic aromatic hydrocarbons (PAHs) are composed of a number of aromatic rings. They are produced because of the incomplete burning of many organic materials like gasoline, charcoal, burning biomass during forest fires, or oil. Consumption of products from sources contaminated by PAHs may be harmful to humans and other animals, as many of these compounds have been involved in causing tumors in animals and cancer in humans. Thus, degradation of these hazardous contaminants is of utmost importance to maintain a clean and healthy environment. While various physicochemical methods have been employed to eliminate these compounds from our surroundings, there are several limitations, like being costly and producing harmful end products. Micro-organisms have an enormous potential for bioremediation, given that they are capable of processing and degrading PAHs. Also, they provide an eco-friendly method of remediation. This review primarily focuses on different PAHs and relevant bioremediation techniques for PAH degradation, either directly or indirectly (rhizoremediation). Further, several genes encoding PAH-catabolic enzymes accountable for effective PAH degradation have also been discussed, along with strategies for utilization of bioremediation at the field level.