Production of New Unsaturated Lipids during Wood Decay by Ligninolytic Basidiomycetes

Abstract

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...

Lignocellulosic polysaccharides and lignin degradation by wood decay fungi: the relevance of nonenzymatic Fenton-based reactions

“…Palmitic and stearic acids have been reported to be produced by some white rot fungi such as Ceriporiopsis subvermispora [56]. However, limited information is available on the production of fatty acids by brown rot fungi, and mechanisms for participation of lipids in brown rot mechanisms have not been proposed.…”

Effect of aqueous extracts from Ceriporiopsis subvermispora-biotreated wood on the decolorization of Azure B by Fenton-like reactions

“…The Fe 3þ -reducing activity found in untreated wood aqueous extracts can be attributed to extractives such as catechols (Aguiar et al, 2006). C. subvermispora has proved to degrade the extractive components in wood (Gutiérrez et al, 2002) which could explain the initial decrease in the Fe 3þ -reducing activities. In fact, the total catechols in the extracts were shown to be totally degraded after the first week of cultivation (Table 1).…”

Mecanismos envolvidos na biodegradação de materiais lignocelulósicos e aplicações tecnológicas correlatas

“…Recentemente, Gutiérrez e colaboradores 73 analisaram cultivos de quatro espécies de basidiomicetos na biodegradação de eucalipto, incluindo P. radiata, Pleurotus pulmonarius, B. adusta e C. subvermispora. Foi identificada uma nova classe de lipídeos dicarboxílicos de cadeia longa, sendo alguns deles insaturados, os quais se acumularam principalmente nas culturas de C. subvermispora (24 mg/100 g de madeira).…”