IN-VITRO DEGRADATION OF NATURAL INSOLUBLE LIGNIN IN AQUEOUS-MEDIA BY THE EXTRACELLULAR PEROXIDASES OF PHANEROCHAETE-CHRYSOSPORIUM

The lignin peroxidases (LIP) and manganese peroxidases (MNP) of Phaner ochaete chrysosporium catalyze a wide range of lignin depolymerization reactions with lignin models and synthetic lignins in solution. Howev er, their ability to degrade insoluble natural lignin in aqueous media has not been demonstrated. Insoluble isolated poplar lignin similar t o natural lignin was treated in vitro in aqueous media for 12 h with L IP, MNP, and both. Treatment with MNP alone slightly increased the sol id mass and produced measurable amounts of lignin-derived 2,6-dimethox yhydroquinone and 2-methoxyhydroquinone but did not appreciably decrea se the total lignin content. Treatment with LIP alone did not decrease the mass but produced measurable amounts of lignin-derived p-hydroxyb enzoic acid and slightly decreased the lignin content. Finally, treatm ent with LIP and MNP together decreased the solid mass by 11%, decreas ed the lignin content by 5%, and released low-concentration compounds with mass spectra containing the typical lignin-derived electron-impac t fragments of mass 107, 137, 151, 167, and 181. These results suggest that MNP increases the effectiveness of LIP-mediated lignin degradati on. (C) 1998 John Wiley & Sons, Inc.