SummaryThe fungal degradation of lipophilic extractives in sapwood and heartwood from Scots pine (Pinus sylvestris) was studied. In sapwood, the white rot fungi,Bjerkanderasp. andFunalia trogii, removed higher amounts of extractives than the sapstain strains,Ophiostoma ainoaeandCeratocystis allantospora. Triglycerides, long chain fatty acids, steryl esters and waxes in pine sapwood were almost completely degraded by all the fungi. Sterols and resin acids were also extensively degraded by the white rot strains; however, these components were not or only poorly removed by the sapstain fungi. The removal of total extractives by all the fungal strains was higher in sapwood as compared to heartwood. The highly concentrated extractive fraction in pine heartwood mainly consists of resin acids. As observed in sapwood, sapstain were also poorly effective in the degradation of the resin acids present in heartwood. The fungal degradation of heartwood extractives was not only limited by the degradative ability of the various test microorganisms, but also by the inhibitory effect exerted by the extractive fraction. The white rot fungusF. trogiiwas particularly inhibited on heartwood.Bjerkanderasp. showed a higher tolerance to toxic extractives and was the most efficient fungus in degrading extractive constituents in both Scots pine heartwood and sapwood. Therefore,Bjerkanderasp. strain BOS55 should be considered as a potential agent for pitch control in pulp and paper manufacture.

Lipids were analyzed by gas chromatography-mass spectrometry for a 7-week in vitro decay of eucalypt wood by four ligninolytic basidiomycetes. The sound wood contained up to 75 mg of lipophilic compounds per 100 g of wood. Hydrolysis of sterol esters, which represented 38% of total wood lipids, occurred during the fungal decay. The initial increase of linoleic and other free unsaturated fatty acids paralleled the decrease of sterol esters. Moreover, new lipid compounds were found at advanced stages of wood decay that were identified from their mass spectra as unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C-3 position of itaconic acid. These dicarboxylic acids were especially abundant in the wood treated with Ceriporiopsis subvermispora (up to 24 mg per 100 g of wood) but also were produced by Phlebia radiata, Pleurotus pulmonarius, and Bjerkandera adusta. We hypothesize that three main alkylitaconic acids (tetradecylitaconic, cis-7-hexadecenylitaconic, and hexadecylitaconic acids) are synthesized by fungi in condensation reactions involving palmitic, oleic, and stearic acids. We suggest that both wood unsaturated fatty acids (present in free form or released from esters during natural decay) and unsaturated metabolites synthesized by fungi could serve as a source for peroxidizable lipids in lignin degradation by white rot basidiomycetes.Fungi produce a variety of lipids including fatty acids in free or esterified form, e.g., glycerides, phospholipids, glycolipids, sterol esters, sphingolipids, or simple esters, as well as other lipids, e.g., free sterols, sterol glycosides, and hydrocarbons (46,54,56). Vegetative mycelium (from pure cultures) and fruit bodies of basidiomycetes differ in both lipid content and fatty acid profiles. Linoleic (18:2 9c,12c ), oleic (18:1 9c ), and palmitic (16:0) acids are the main fatty acids in most cases. Linoleic acid is very abundant in fruit bodies and may account for as much as 70 to 80% of the lipids present (1,42,48,49). Other saturated and unsaturated fatty acids are present in basidiomycetes at lower levels. As reported for other filamentous fungi, unsaturated fatty acids could help basidiomycetes adapt to low growth temperatures (11,12). These fatty acids also may have a role in lignin degradation.Lipid peroxidation reactions could be a part of the lignin degradation process by white rot basidiomycetes. When unsaturated fatty acids are oxidized in the presence of manganese peroxidase (MnP), a ligninolytic peroxidase that oxidizes Mn 2ϩ to Mn 3ϩ , lipid hydroperoxides and free radicals are formed. This reaction is considered to be sufficient for lignin degradation by some ligninolytic fungi, e.g., Ceriporiopsis (syn. Poria) subvermispora, that lack lignin peroxidase (LiP) (4, 31-33). LiP, which has a high redox potential that enables direct oxidation of nonphenolic lignin units, was described in the white rot fungus Phanerochaete chrysosporium together with MnP (37). However, LiP has not been detected in some efficient lignin-degrading...

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