Biodegradation of Compression Wood and Tension Wood by White and Brown Rot Fungi

Abstract

Ultrastructural investigations and chemical determinations of Compression wood frorn Abies balsamea, Picea mariana and Pinus strobits after decay by white or brown rot fungi demonsträted that this type of wood is more resistant to decay than normal wood. Hyphae colonizing Compression wood were found in cell lumina and intercellular spaces whereas normal wood cell had hyphae only in cell lumina. Compression wood did not alter the type of cell wall degradation produced by the various fungi tested, but the rate and extent of decay were limited. The white rot fungus, Trametes versicolor, caused a nonselective attack of all cell wall components äs indicated by erosion of secondary wall layers and middle lamellae. A selective removal of lignin occurred throughout the cell walls of wood decayed by the other white rot fungi (Phellinus pini, Phlebia tremellosa and Scytinostroma galactimim) that were evaluated. The brown rot fungi, Fomitopsis pinicola and Oligoporus placentus caused a diffuse removal of polysaccharides from both compression wood and normal wood. Tension wood from Populus tremuloides and Acer rubrum decayed by white or brown rot fungi had similar amounts of decay to those observed in normal wood. Ultrastructural observations, however, showed striking differences in the progressive stages of decay. Hyphae of Trametes versicolor located in cell lumina did not cause erosion or severe degradation of the adjacent, underlying gelatinous iayer associated with tension wood. A typical nonselective degradation of the secondary wall layers and middle lamellae, however, occurred beneath this gelatinous layer. In areas of advanced degradation, the secondary walls and middle lamellae between cell walls were completely degraded leaving only the gelatinous layer and cell corner regions of the middle lamellae. Brown rot fungi were able to degrade the gelatinous layer and other cell wall layers resulting in extensive degradation of polysaccharides.

Chemical Imaging of Poplar Wood Cell Walls by Confocal Raman Microscopy

“…The occurrence of lignin in the G-layer during tension wood formation has long been debated (Pilate et al, 2004a). Some studies concluded that the G-layer mostly consists of cellulose and is totally free of lignin (Blanchette et al, 1994;Wada et al, 1995;Donaldson, 2001), whereas others found evidence for lignin (Yoshida et al, 2002;Joseleau et al, 2004). In this study, within the main part of the G-layer, lignin bands were weak, thus pointing to very minor amounts of lignin (Fig.…”

Detection in situ and characterization of lignin in the G -layer of tension wood fibres of Populus deltoides

“…It was therefore of interest to re-assess lignification in tension wood with novel approaches having higher sensitivity and specificity than the previously used techniques. Former studies of lignin in tension wood relied either on highly drastic methods such as the lignin skeleton method using hydrofluoric acid (Parham and Coˆte´1971) or staining methods such as KMnO 4 (Blanchette et al 1994). Both techniques lack the sensitivity allowing detection of discrete amounts of lignin amid a large amount of polysaccharides.…”

Relevância de compostos de baixa massa molar produzidos por fungos e envolvidos na biodegradação da madeira

“…20 Os fungos causadores de decomposição parda degradam principalmente os polissacarídeos (celulose e polioses) presentes na madeira, 21,22 ao passo que a lignina é somente modificada estruturalmente, sendo a desmetoxilação a principal alteração ocorrida na estrutura da lignina, com pouca oxidação da cadeia lateral. 23,24 Entretanto, alguns estudos mais recentes mostram perda substancial de lignina (acima de 20%, lignina Klason) durante a biodegradação da madeira por algumas espécies causadoras de decomposição parda, 18,25,26 e que esta perda é aumentada em estágios mais avançados de degradação. 18,26 Todavia, esta perda pode estar associada com a liberação de metanol proveniente das reações de desmetoxilação e não com a degradação da lignina propriamente dita.…”