Wood stimulates the demethoxylation of [O14CH3]-labeled lignin model compounds by the white-rot fungi Phanerochaete chrysosporium and Phlebia radiata |
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Authors: | Outi Niemenmaa Antti Uusi-Rauva Annele Hatakka |
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Institution: | (1) Department of Applied Chemistry and Microbiology, University of Helsinki, Viikki Biocenter, Viikinkaari 9, P.O. Box 56, 00014 Helsinki, Finland;(2) Instrument Centre of the Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland |
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Abstract: | Mineralization of polymeric wood lignin and its substructures is a result of complex reactions involving oxidizing and reducing enzymes and radicals. The degradation of methoxyl groups is an essential part of this process. The presence of wood greatly stimulates the demethoxylation of a non-phenolic lignin model compound (a O14CH3]-labeled β-O-4 dimer) by the lignin-degrading white-rot fungi Phlebia radiata and Phanerochaete chrysosporium. When grown on wood, both fungi produced up to 47 and 40% 14CO2 of the applied 14C activity, respectively, under air and oxygen in 8 weeks. Without wood, the demethoxylation of the dimer by both fungi was lower, varying between 0.5 and 35%. Addition of nutrient nitrogen together with glucose decreased demethoxylation when the fungi were grown on spruce wood under air. Because the evolution of 14CO2 in the absence of wood was poor, the fungi may have preferably used wood as a carbon and nitrogen source. The amount of fungal mycelium, as determined by the ergosterol assay, did not show connection to demethoxylation. P. radiata also showed a high demethoxylation of O14CH3]-labeled vanillic acid in the presence of birch wood. The degradation of lignin and lignin-related substances should be studied in the presence of wood, the natural substrate for white-rot fungi. |
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Keywords: | White-rot fungi Phanerochaete chrysosporium Phlebia radiata Demethoxylation Lignin-related dimer Vanillic acid Wood Ergosterol |
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