Microbial biodegradation is an effective way to protect human health from polluted environments contaminated with highly toxic and carcinogenic chemicals such as polycyclic aromatic hydrocarbons (PAHs). Persistence of PAHs at these sites is due to the resistance of high m.w. PAHs (4-5 ring) to biodegradation by natural microflora. This necessitates the use of appropriate bioremediation agents and strategies that can enhance biodegradation of these recalcitrant PAHs. Our focus is on the wood-rotting white rot fungus Phanerochaete chrysosporium. Despite its extraordinary biodegradation potential, little is known on the enzymatic processes and conditions required for effective field application of this fungal agent in bioremediation of resistant PAHs in the environment. Using functional genomic approach, we have identified a subset of PAH-inducible P450 monooxygenase genes in P. chrysosporium, which are expressible under more varied nutrient conditions unlike the previously characterized peroxidases. We will test our hypothesis that an effective bioremediation activity of the white rot fungus toward higher PAHs (4-5 ring) can be achieved in a biphasic approach involving optimized initial expression of its promising P450 monooxygenases (for initial oxidation) preceding the expression of ligninolytic enzymes (for subsequent biotransformation/ mineralization to CO2) with nutrient depletion such as on lignocellulose. The overall goal of this research is to gain an understanding of the promising P450 system for use in P450-initiated biodegradation of PAHs in this organism as a basis for developing effective bioremediation strategies.
The specific aims are (1) Functional expression of the candidate P450s to select the promising PAH-oxidizing P450(s) and generate P450 fungal biocatalyst(s);(2) Investigate catalytic activity of the developed P450 biocatalyst(s) and further biodegradability and toxicity reduction of the P450-oxidation products of PAHs by white rot fungus. (3) Optimize conditions for enhanced expression of the newly-identified PAH-oxidizing P450 vis-a-vis the ligninolytic peroxidases using varied treatment conditions;(4). Evaluate the optimized conditions and developed P450 biocatalysts for bioremediation of PAHs by the white rot fungus. The studies are expected to provide a knowledgebase for development of effective bioremediation technologies for recalcitrant PAHs based on the use of white rot fungus.
Microbial biodegradation is an effective way to protect human health from polluted environments contaminated with highly toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs). This proposal will develop appropriate fungal biocatalysts and strategies for PAH bioremediation.
