PYROLYSIS GAS-CHROMATOGRAPHY MASS-SPECTROMETRY OF MILLED WOOD LIGNIN OF 2 CHILEAN WOODS NATURALLY DECAYED BY GANODERMA-AUSTRALE, PHLEBIA-CHRYSOCREA AND A BROWN-ROT FUNGUS

Two native Chilean woods (Eucryphia cordifolia Cav, and Laurelia phili ppiana Looser) and their corresponding sound and degraded milled wood lignin preparations, were characterized by pyrolysis-gas chromatograph y/mass spectrometry. The main goal of this work was to study the chemi cal changes in a lignin molecule during the natural fungal decay. A hi gher proportion of syringyl (S) than guaiacyl (G) units was detected i n the native wood of E. cordifolia (S/G ratio of 3.9), whereas L. phil ippiana native wood showed similar amounts of S and G units (S/G ratio of 0.9). The modified Bjorkman method used here proved to be a suitab le procedure for removing almost all the carbohydrate fraction of wood , with only minor modifications (demethylations) to the resulting puri fied lignin. The alterations affecting the propane chain of lignin uni ts (C-3-alkyl chain oxidations and shortenings) observed in L, philipp iana after Phlebia chrysocrea (Berk. and Curt.) decay were similar to these described in E. cordifolia by Ganoderma australe (Fr.), except t hat the former were only detected in S-lignin units. Additionally, in L. philippiana some demethylation reactions were also suggested, altho ugh oxidations were not observed in the C-beta-position. Both fungi pr oduced a decrease in lignin content, independent of the different S/G ratio of the studied woods. After the brown-rot fungus attack the lign in content did not change. Although this brown-rot microorganism does not substantially degrade lignin, it is able to produce some minor che mical alterations: demethylations and oxidations of lignin side-chains .