Multidimensional NMR analysis reveals truncated lignin structures in wood decayed by the brown rot basidiomycete Postia placenta

The wood is a material of biological origin and because of its chemical composition is subject to the attack of various organisms that use it as a source of food. Thus, this study aimed to evaluate the natural durability and chemical composition of the Liquidambar sp. wood. Were performed the accelerated laboratory test, with a pure culture of the Postia placenta fungus, causer of brown rot , and no choice-feeding of termites Nasutitermes corniger. After both tests, the samples were dried in an oven at 103 ± 2ºC until reaching constant mass and later weighed, to evaluate the percentage of mass loss. The contents of extractives, soluble, insoluble and total lignin, and holocellulose were also determined. The studied wood obtained losses of mass of 37.79% and 23.37%, when submitted to the action of fungus and termites, respectively, and an average extractive content equal to 4.13%. It is concluded that the Liquidambar sp. wood was moderate resistance to the attack of the brown rot fungus, and little resistant to the action of employed termites.

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Myofibrillar cell wall extensions in the hyphal sheath of Postia placenta

Canadian Journal of Microbiology ◽

10.1139/m92-147 ◽

1992 ◽

Vol 38 (9) ◽

pp. 905-911 ◽

Cited By ~ 9

Author(s):

Michael J. Larsen ◽

Frederick Green III

Keyword(s):

Cell Wall ◽

Brown Rot ◽

Decay Process ◽

Structural Components ◽

Hyphal Cell ◽

Postia Placenta ◽

Glass Cover ◽

Hyphal Sheath ◽

Brown Rot Decay ◽

Extracellular Structures

Evidence is provided for the existence of linear extracellular fibrillar elements in the brown-rot fungus Postia placenta. These elements appear as structural components of the hyphal sheath and more closely resemble mycofibrils than fungal fimbriae. Mycofibrils are associated with and appear to originate from the hyphal surface when hyphae are grown on wood or inert substrates, such as glass cover slips and polycarbonate filters. These extracellular structures have a nominal diameter of 10–50 nm and are up to 25 μm in length. We conclude that mycofibrils are linear structural extensions of the hyphal cell wall. The precise function of mycofibrils in the brown-rot decay process of wood remains to be elucidated. Key words: Postia placenta, mycofibrils, fungal fimbriae, hyphal sheath, electron microscopy.

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Thermal Stability and Decay Resistance Properties of Tropical Wood Polymer Nanocomposites (WPNC)

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.667.482 ◽

2013 ◽

Vol 667 ◽

pp. 482-489 ◽

Cited By ~ 3

Author(s):

Md. Saiful Islam ◽

Sinin Hamdan ◽

Mohamad Rusop ◽

Md. Rezaur Rahman

Keyword(s):

Thermal Stability ◽

Polymer Nanocomposites ◽

Phenol Formaldehyde ◽

Brown Rot ◽

Decay Resistance ◽

White Rot ◽

Postia Placenta ◽

Tropical Wood ◽

Wood Polymer ◽

The Fourier Transform

The effects of nanoclay on the thermal stability and decay resistance properties of tropical wood polymer nanocomposites (WPNCs) were investigated in this work. WPNC were prepared from several selected tropical wood species by impregnating the selected woods with a combination of nanoclay and phenol formaldehyde (PF) prepolymer mixture. The formation of WPNC was confirmed by the fourier transform infrared spectroscopy (FTIR) analysis. Thermal property of manufactured WPNC in terms of thermogravimetric analysis (TGA) was evaluated, and an improvement in thermal stability was found for fabricated WPNC. The wood was then exposed to two types of fungi; white-rot (polyporous versicolor) and brown-rot (postia placenta), for 12 weeks. Decay was assessed through percentage (%) of weight loss. A significant improvement was found in the treated woods compared to the untreated ones. In addition, the fabricated WPNC showed lower moisture content compared with raw one.

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Laccase and Its Role in Production of Extracellular Reactive Oxygen Species during Wood Decay by the Brown Rot Basidiomycete Postia placenta

Applied and Environmental Microbiology ◽

10.1128/aem.02929-09 ◽

2010 ◽

Vol 76 (7) ◽

pp. 2091-2097 ◽

Cited By ~ 69

Author(s):

Dongsheng Wei ◽

Carl J. Houtman ◽

Alexander N. Kapich ◽

Christopher G. Hunt ◽

Daniel Cullen ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Protein Identification ◽

Reactive Oxygen ◽

Wood Decay ◽

Brown Rot ◽

Order Rate Constant ◽

Spectrometric Analysis ◽

Alternative Mechanism ◽

Oxygen Species ◽

Postia Placenta

ABSTRACT Brown rot basidiomycetes initiate wood decay by producing extracellular reactive oxygen species that depolymerize the structural polysaccharides of lignocellulose. Secreted fungal hydroquinones are considered one contributor because they have been shown to reduce Fe3+, thus generating perhydroxyl radicals and Fe2+, which subsequently react further to produce biodegradative hydroxyl radicals. However, many brown rot fungi also secrete high levels of oxalate, which chelates Fe3+ tightly, making it unreactive with hydroquinones. For hydroquinone-driven hydroxyl radical production to contribute in this environment, an alternative mechanism to oxidize hydroquinones is required. We show here that aspen wood undergoing decay by the oxalate producer Postia placenta contained both 2,5-dimethoxyhydroquinone and laccase activity. Mass spectrometric analysis of proteins extracted from the wood identified a putative laccase (Joint Genome Institute P. placenta protein identification number 111314), and heterologous expression of the corresponding gene confirmed this assignment. Ultrafiltration experiments with liquid pressed from the biodegrading wood showed that a high-molecular-weight component was required for it to oxidize 2,5-dimethoxyhydroquinone rapidly and that this component was replaceable by P. placenta laccase. The purified laccase oxidized 2,5-dimethoxyhydroquinone with a second-order rate constant near 104 M−1 s−1, and measurements of the H2O2 produced indicated that approximately one perhydroxyl radical was generated per hydroquinone supplied. Using these values and a previously developed computer model, we estimate that the quantity of reactive oxygen species produced by P. placenta laccase in wood is large enough that it likely contributes to incipient decay.

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