MONITORING OF CHEMICAL-CHANGES IN WHITE-ROT DEGRADED BEECH WOOD BY PYROLYSIS-GAS CHROMATOGRAPHY AND FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Fagus sylvatica L. (beech) wood was degraded under laboratory conditions by the white-rot fungi Trametes versicolor, Pleurotus ostreatus and Lentinus edodes. The weight loss of the samples were 51, 27, and 24%, respectively. Compared to polysaccharides, lignin determination accounted for a slightly preferential lignin degradation by the fungi. The residual wood after fungal attack was investigated by FT-IR spectroscopy (transmission mode) and analytical pyrolysis (resistance heating, Pyroprobe 100). Both the FT-IR spectra and analytical pyrolysis revealed that the lignin moiety of the samples was modified more than the polysaccharide part. In the FT-IR spectra, the intensity of the conjugated C = O groups was increased proportionally to the sample's weight loss. The pyrograms reflect the fungal degradation. The degraded woods have more phenolic products with double bonds in the side chain and the carbohydrate derived pyrolysis products also show changes. The pyrograms were compared by normalization and calculation of congruence indices. Within the lignin fraction, the guaiacyl content changed to a larger extent than the syringyl while the guaiacyl/syringyl ratio slightly increased. Pyrolysis data slightly overestimates the lignin content of the degraded samples.