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Metabolism of phenanthrene by Phanerochaete chrysosporium
J B Sutherland1, A L Selby, J P Freeman
1National Center for Toxicological Research, Food and Drug Administration, Jefferson, Arkansas 72079.
Abstract:
The white rot fungus Phanerochaete chrysosporium metabolized phenanthrene when it was grown for 7 days at 37 degrees C in a medium containing malt extract, D-glucose, D-maltose, yeast extract, and Tween 80. After cultures were grown with [9-14C]phenanthrene, radioactive metabolites were extracted from the medium with ethyl acetate, separated by high-performance liquid chromatography, and detected by liquid scintillation counting. Metabolites from cultures grown with unlabeled phenanthrene were identified as phenanthrene trans-9,10-dihydrodiol, phenanthrene trans-3,4-dihydrodiol, 9-phenanthrol, 3-phenanthrol, 4-phenanthrol, and the novel conjugate 9-phenanthryl beta-D-glucopyranoside. Identification of the compounds was based on their UV absorption, mass, and nuclear magnetic resonance spectra. Since lignin peroxidase was not detected in the culture medium, these results suggest the involvement of monooxygenase and epoxide hydrolase activity in the initial oxidation and hydration of phenanthrene by P. chrysosporium.
Insights
The white rot fungus Phanerochaete chrysosporium breaks down phenanthrene, a polycyclic aromatic hydrocarbon. It produces novel metabolites, indicating specific enzymatic pathways are involved in its degradation.
Area of Science:
- Environmental microbiology
- Bioremediation
- Fungal metabolism
Background:
- Polycyclic aromatic hydrocarbons (PAHs) like phenanthrene are environmental pollutants.
- White rot fungi, such as Phanerochaete chrysosporium, are known for their ability to degrade complex organic compounds.
- Understanding the metabolic pathways of phenanthrene degradation is crucial for bioremediation strategies.
Purpose of the Study:
- To investigate the metabolic fate of phenanthrene by Phanerochaete chrysosporium.
- To identify the metabolites produced during phenanthrene degradation.
- To elucidate the enzymatic mechanisms involved in the initial steps of phenanthrene oxidation and hydration.
Main Methods:
- Culturing Phanerochaete chrysosporium in a defined medium with phenanthrene.
- Using radiolabeled [9-14C]phenanthrene to track metabolites.
- Extraction and separation of metabolites using ethyl acetate and high-performance liquid chromatography (HPLC).
- Detection and identification of metabolites using liquid scintillation counting, UV absorption, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy.
Main Results:
- Phanerochaete chrysosporium metabolized phenanthrene over a 7-day incubation period.
- Identified metabolites include phenanthrene trans-9,10-dihydrodiol, phenanthrene trans-3,4-dihydrodiol, 9-phenanthrol, 3-phenanthrol, 4-phenanthrol, and a novel conjugate, 9-phenanthryl beta-D-glucopyranoside.
- Lignin peroxidase activity was not detected in the culture medium.
Conclusions:
- The results suggest that monooxygenase and epoxide hydrolase activities are primarily responsible for the initial oxidation and hydration of phenanthrene by Phanerochaete chrysosporium.
- The novel conjugate identified points to further metabolic modifications.
- These findings contribute to understanding fungal degradation pathways for PAHs and inform bioremediation approaches.