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.

Public Health Relevance

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.

National Institute of Health (NIH)
National Institute of Environmental Health Sciences (NIEHS)
Research Project (R01)
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Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
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Thompson, Claudia L
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University of Cincinnati
Public Health & Prev Medicine
Schools of Medicine
United States
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Bhattacharya, Sukanta S; Syed, Khajamohiddin; Shann, Jodi et al. (2013) A novel P450-initiated biphasic process for sustainable biodegradation of benzo[a]pyrene in soil under nutrient-sufficient conditions by the white rot fungus Phanerochaete chrysosporium. J Hazard Mater 261:675-83
Syed, Khajamohiddin; Nelson, David R; Riley, Robert et al. (2013) Genomewide annotation and comparative genomics of cytochrome P450 monooxygenases (P450s) in the polypore species Bjerkandera adusta, Ganoderma sp. and Phlebia brevispora. Mycologia 105:1445-55
Syed, Khajamohiddin; Porollo, Aleksey; Miller, David et al. (2013) Rational engineering of the fungal P450 monooxygenase CYP5136A3 to improve its oxidizing activity toward polycyclic aromatic hydrocarbons. Protein Eng Des Sel 26:553-7
Syed, Khajamohiddin; Porollo, Aleksey; Lam, Ying Wai et al. (2013) CYP63A2, a catalytically versatile fungal P450 monooxygenase capable of oxidizing higher-molecular-weight polycyclic aromatic hydrocarbons, alkylphenols, and alkanes. Appl Environ Microbiol 79:2692-702
Syed, Khajamohiddin; Yadav, Jagjit S (2012) P450 monooxygenases (P450ome) of the model white rot fungus Phanerochaete chrysosporium. Crit Rev Microbiol 38:339-63
Syed, Khajamohiddin; Porollo, Aleksey; Lam, Ying Wai et al. (2011) A fungal P450 (CYP5136A3) capable of oxidizing polycyclic aromatic hydrocarbons and endocrine disrupting alkylphenols: role of Trp(129) and Leu(324). PLoS One 6:e28286
Syed, Khajamohiddin; Kattamuri, Chandramohan; Thompson, Thomas B et al. (2011) Cytochrome b? reductase-cytochrome b? as an active P450 redox enzyme system in Phanerochaete chrysosporium: atypical properties and in vivo evidence of electron transfer capability to CYP63A2. Arch Biochem Biophys 509:26-32
Syed, Khajamohiddin; Doddapaneni, Harshavardhan; Subramanian, Venkataramanan et al. (2010) Genome-to-function characterization of novel fungal P450 monooxygenases oxidizing polycyclic aromatic hydrocarbons (PAHs). Biochem Biophys Res Commun 399:492-7
Subramanian, Venkataramanan; Doddapaneni, Harshavardhan; Syed, Khajamohiddin et al. (2010) P450 redox enzymes in the white rot fungus Phanerochaete chrysosporium: gene transcription, heterologous expression, and activity analysis on the purified proteins. Curr Microbiol 61:306-14
Subramanian, Venkataramanan; Yadav, Jagjit S (2009) Role of P450 monooxygenases in the degradation of the endocrine-disrupting chemical nonylphenol by the white rot fungus Phanerochaete chrysosporium. Appl Environ Microbiol 75:5570-80