Abstract.
The fungal ligninolytic enzyme manganese peroxidase (MnP) is known to function by oxidizing Mn(II) to Mn(III), a powerful oxidant. In this work, an abiotic system consisting of Mn(III) in oxalate buffer under aerobic conditions (Mn(III)/oxalate/O2 system) was shown to be capable of extensively transforming 2-amino-4,6-dinitrotoluene (2A46DNT) – one of the main reduction products of 2,4,6-trinitrotoluene (TNT). No significant transformation occurred in the presence of other organic acids or under anaerobic conditions. The Mn(III)/oxalate/O2 system was also able to transform other nitroaromatic compounds such as 2-nitrotoluene, 4-nitrotoluene, 2,4-dinitrotoluene, TNT – the latter to a lesser extent –, and their reduction derivatives. The Mn(III)/oxalate/O2 system mineralized 14C-U-ring labeled 2A46DNT slightly, while no significant mineralization of 14C-U-ring labeled TNT was observed. Unidentified 14C-transformation products were highly polar. Electron spin resonance experiments performed on the Mn(III)/oxalate/O2 system revealed the generation of formyl free radicals (·COO–). The oxygen requirement for the transformation of nitroaromatic compounds suggests the involvement of superoxide free radicals (% MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfKttLearuavTnhis1MBaeXatLxBI9gBam % XvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2DaeHbuLwB % Lnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8YjY-vipgYlH8Gipe % c8Eeeu0xXdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXd % ar-Jb9hs0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaaiaacaqabeaada % abauaaaOqaaiabb+eapnaaDaaaleaacqaIYaGmaeaacqGHsislkiab % gwSixdaaaaa!3F2C! \( {\rm O}_2^{ - \cdot } \) ), produced through autoxidation of ·COO– by molecular oxygen. The implication of such a Mn(III)/oxalate/O2 system in the MnP-catalyzed degradation of nitroaromatic pollutants by white-rot fungi is further discussed.
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Received revision: 22 October 2001
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Van Aken, .B., Agathos, .S. Implication of manganese (III), oxalate, and oxygen in the degradation of nitroaromatic compounds by manganese peroxidase (MnP). Appl Microbiol Biotechnol 58, 345–351 (2002). https://doi.org/10.1007/s00253-001-0888-1
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DOI: https://doi.org/10.1007/s00253-001-0888-1