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A study of Eucryphia cordifolia wood extensively degraded by white-rot and brown-rot fungi by pyrolytic and spectroscopic techniques

AutorMartínez, Ángel T. ; Rencoret, Jorge ; Nieto, Lidia ; Jiménez-Barbero, Jesús ; Gutiérrez Suárez, Ana ; Río Andrade, José Carlos del
Fecha de publicación2010
EditorInstitut national de la recherche agronomique (France)
Université de Reims
Citación1st Symposium on Biotechnology Applied to Lignocelluloses-LignoBiotech One: (2010)
ResumenWhite-rot and brown-rot basidiomycetes are attracting considerable attention as two models for different strategies of wood attack of interest in future lignocellulose biorefineries, resulting in the sequencing of the corresponding genomes and other studies (Martinez D et al. Nat. Biotechnol. 22, 695, 2004; and Proc. Natl. Acad. Sci. USA 106, 1954, 2009). In the present study the structural characteristics of Eucryphia cordifolia woods extensively degraded by a white-rot fungus and a brown-rot fungus have been studied using pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS) and nuclear magnetic resonance (NMR) spectroscopy (by comparing with the initial wood). Py-GC/MS was performed both in the absence and in the presence of tetrabutylammonium hydroxide (TBAH) the latter resulting in alkaline degradation followed by butylation of products to be analyzed by GC/MS. For the NMR analyses, the changes were analysed “in situ” by 2D-NMR (using HSQC experiments) of the whole wood sample by using a method that consists in swelling finely ground samples in dimethylsulfoxide (DMSO-d6) and forming a gel in the NMR tube, and compared with results from solid-state 13C NMR. The study of the white-rotted wood showed the presence of only carbohydrate moieties and the complete absence of lignin moieties, either in the NMR spectra and in the pyrograms, indicating that the lignin polymer was completely removed during the fungal decay. On the other hand, the analyses of the brown-rotted wood showed the absence of carbohydrate moieties, and only the lignin polymer was present. In contrast with other reports, the data obtained indicated that the lignin polymer was not extensively modified by the brown-rot fungus, most of the lignin structure remaining unaltered. This included well-resolved signals of side-chains in β-O-4' and β-β' lignin substructures (minor spirodienones found in wood were not detected after the brown-rot decay) together with strong aromatic signals of syringyl and guaiacyl units in the HSQC (and 13C) NMR spectra. A small increase of oxygenated moieties was observed among the pyrolysis products, indicating that some oxidative alterations in the lignin structure occurred during decay, in agreement with the comparatively higher intensity of the HSQC signal corresponding to 1H2,6-13C2,6 correlation in α-oxidized syringyl units. Moreover, several compounds with 5-hydroxyguaiacyl skeleton were released upon Py-GC/MS and Py/TBAH, indicating that some demethylation also occurred during brown-rot decay, however, this did not appear to be extensive according to the information provided by the HSQC spectra. This study has been supported by the BIORENEW EU-project (NMP2-CT-2006-026456).
DescripciónComunicación presentada al citado simposio, celebrado del 28 de marzo al 1 de abril 2010, en Reims, Francia.-- cmartin@irnase.csic.es
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