title: Selective lignin and polysaccharide removal in natural fungal decay of wood as evidenced by in situ structural analyses.
abstract: Selective modification/degradation of the main plant polymers (cellulose, hemicelluloses and lignin) was investigated in a hardwood after white and brown-rot fungal decay under environmental conditions. The chemical changes produced in the plant cell wall were analysed in situ, by nuclear magnetic resonance (NMR) at the gel state, and analytical pyrolysis. Two-dimensional (2D) NMR of the white-rotted wood showed only cellulose and (deacetylated) hemicellulose, and the complete removal of lignin. On the other hand, the brown-rotted wood showed the nearly complete absence of polysaccharides, while the main features of lignin structure, as revealed by 2D-NMR, could be observed. These included well-resolved aromatic and side-chain cross-signals, although the intensity of the latter signals was lowered indicating a reduction in the number of side-chain linkages (β-O-4' and β-β') per aromatic unit (their relative abundances remaining unchanged). These results contrast with a recent study concluding that the aromatic polymer after brown-rot decay is not longer recognized as lignin. Some oxidative alteration of lignin during brown-rot decay was evidenced and, more interesting, several compounds with 3-methoxycatechol skeleton were released upon pyrolysis. Lignin demethylation is consistent with recent brown-rot transcriptomic/secretomic studies showing overexpression of methanol oxidase, which could use lignin-derived methanol to generate the peroxide required for cellulose depolymerization via Fenton chemistry.
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080-Seville, Spain.
authors.forename: Angel T
authors.initials: AT
authors.lastname: Martínez
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080-Seville, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Rencoret
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080-Seville, Spain.
authors.forename: Lidia
authors.initials: L
authors.lastname: Nieto
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080-Seville, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Jiménez-Barbero
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080-Seville, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Gutiérrez
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, E-41080-Seville, Spain.
authors.forename: José C
authors.initials: JC
authors.lastname: Del Río
mesh_terms: D002473:Cell Wall / Q000737:chemistry*; D005658:Fungi / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D008031:Lignin / Q000032:analysis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000032:analysis / Q000737:chemistry*; D014934:Wood / Q000737:chemistry*
chemical_list: D011134:Polysaccharides; C007916:hemicellulose; D008031:Lignin