Mechanistic understanding and future prospect of microbe-enhanced phytoremediation of polycyclic aromatic hydrocarbons in soil

Restoring polluted land is a time-consuming endeavor due to the difficulty inherent in the process. The quality of soil considerably worsens with the addition of toxic persistent organic pollutants (POPs) of industrial origin. Industrialization results in millions of tonnes of POPs worldwide, which pose a threat to surrounding ecosystems. In India alone, oil refineries generate approximately 28,000 tonnes of oily sludge (toxic organic compounds) per annum containing POPs-polycyclic aromatic hydrocarbons (PAHs). These PAHs have existed in environments throughout the globe for the last several decades due to long half-lives. The fate of PAHs and their residues pose a threat to all forms of life. High levels of the 16 PAHs (US EPA) were found in soil in Asia's oldest oil and gas drilling site, with a range spanning from a minimum of 13.48 to a maximum of 86.3 mgkg(-1) due to exploration of crude oil. The management of such a paradoxical situation is a challenge. The mitigation of PAHs by employing plant-microbe systems from soil is a low-cost prospective biotechnological approach. This technology engineers the rhizosphere and helps restoration of degraded land. Recent findings demonstrated how adding biochar (carbon rich phytoproduct) to the soil resulted in positive effects on plant-microbe assisted PAH removal. This review focuses on the mechanistic understanding of plant-microbe assisted remediation. We consider the future prospect to optimize the phytoremediation process through genomics and metabolomics data. The genetic manipulation of plants and microbes seems to have improved the phytoremediation process by utilizing the signaling network of plant-microbe interactions (c) 2018 Elsevier B.V. All rights reserved.