Transformation of 2,4,6-Trinitrotoluene (TNT) Reduction Products by Lignin Peroxidase (H8) from the White-Rot Basidiomycete Phanerochaete chrysosporium |
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Authors: | Benoî t Van Aken James D Stahl Henry Naveau Spiros N Agathos Steven D Aust |
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Institution: | 1. Unit of Bioengineering, Université Catholique de Louvain, Place Croix du Sud 2/19, 1348 Louvain-la-Neuve, Belgium;2. Biotechnology Center, Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-4430 |
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Abstract: | White-rot fungi are known to degrade a wide range of xenobiotic environmental pollutants, including the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). TNT is first reduced by the fungal mycelium to aminodinitrotoluenes and diaminonitrotoluenes. In a second phase, reduced TNT metabolites are oxidatively transformed and mineralized. The extracellular oxidative enzyme of the ligninolytic system of these fungi includes the lignin peroxidases (LiP) and the manganese-dependent peroxidases (MnP). In the present study, we have shown that a cell-free enzymatic system containing fast protein liquid chromatography (FPLC)-purified LiP (H8) from the white-rot fungus Phanerochaete chrysosporium was able to completely transform 50?mg/L of 2,4-diamino-6-nitrotoluene (2,4-DA-6-NT) and 2-amino-4,6-dinitrotoluene (2-A-4,6-DNT) in 1 and 48?h, respectively. Veratryl alcohol (VA), often described as a mediator in the LiP-catalyzed oxidative depolymerization of lignin, was not required for the enzymatic transformation of 2,4-DA-6-NT or 2-A-4,6-DNT. 2,4-DA-6-NT was also shown to be a competitive inhibitor of the LiP activity measured through the oxidation of VA. Experiments using 14C-U-ring labeled compounds showed that 2-A-4,6-DNT was converted to 2,2'-azoxy-4,4' ,6,6'-tetranitrotoluene. No significant mineralization, measured by the release of 14CO2, was observed over 5 d. |
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