Py-GC/MS study of Eucalyptus globulus wood treated with different fungi

The degradation patterns of Eucalyptus globulus wood by several wood-rottin g fungi from the groups of ascomycetes, basidiomycetes and deuteromycetes w ere studied by analytical pyrolysis coupled to gas chromatography/mass spec trometry. The pyrograms of sound and degraded eucalypt wood showed several major peaks from lignin breakdown, identified as guaiacol, 4-methylguaiacol , 4-vinylguaiacol, eugenol, syringol, trans-isoeugenol, 4-methylsyringol, 4 -ethylsyringol, 4-vinylsyringol, 4-allylsyringol, syringaldehyde, trans-4-p ropenylsyringol, acetosyringone, syringylacetone and propiosyringone. Produ cts arising from carbohydrate pyrolysis could also be recognized. Similar p yrolysis compounds were found during analysis of sound and decayed wood, bu t differences were observed in their relative abundances. Relative peak are as were calculated for guaiacyl (G) and syringyl-type (S) lignin breakdown products, as well as for compounds arising from carbohydrates. Several basi diomycetes were found to be the most efficient lignin degraders on eucalypt wood as revealed by lignin/carbohydrate ratio from pyrolysis products. Amo ng them, Poria subvermispora caused the most intense removal of lignin moie ty from eucalypt wood. A decrease of lignin S/G ratio was observed during w ood delignification, the lowest ratio being found also in the wood treated with P. subvermispora. This is due to the preferential biodegradation of et her-linked S-lignin yielding a residue enriched in G-lignin that is more re calcitrant towards fungal attack because of its higher condensation degree. On the other hand, deuteromycetes preferentially degraded the carbohydrate moiety while the ascomycetes included in this study did not show any parti cular preference in the degradation of eucalypt wood constituents. (C) 2001 Elsevier Science B.V. All rights reserved.