An analytical pyrolysis mass spectrometric study of Eucryphia cordifolia wood decayed by white-rot and brown-rot fungi

The decay of Eucryphia cordifolia wood by white-rot and brown-rot fungi was studied with pyrolysis electron impact mass spectrometry (Py(EI)MS) and pyrolysis ammonia chemical ionization mass spectrometry (Py(CI)MS). Py(EI)MS spectra of the wood after decay by the white-rot fungus Ganoderma australe no longer show mass peaks indicative for lignin. The relative abundance of syringyl (dimethoxy) compounds decreases faster than the coniferyl (monomethoxy) compounds. In the same spectra the relative abundance of hexosans increases whereas the relative amount of pentosans remains constant. The presence of oligomeric sugars in the Py(CI)MS spectrum points to a preservation of some polysaccharides. Brown-rot fungal degradation of similar wood samples analysed with Py(EI)MS reveals no mass peaks for polysaccharides, resulting in a spectrum with mass peaks specific for lignin. The Py(EI)MS, revealing lignin dimers, and the Py(CI)MS spectra suggest that the lignin was not modified by the brown-rot fungus. However, the pyrolysis gas chromatography mass spectrometry (PyGCMS) data show an increase in oxygenated lignin pyrolysis products suggesting a molecular change in the lignin due to brown-rotting. In the brown-rotted wood one sugar pyrolysis product (levoglucosan) was observed by Py(CI)MS and PyGCMS suggesting that part of the cellulose polymer system is inaccessible to fungal degradation. Comparing data obtained from ¹³C cross polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) with data obtained from PyMS reveals that the latter method provides much more structural information.