Rapid characterisation of brown and white rot degraded chir pine and rubberwood by FTIR spectroscopy

Pinus roxburghii (chir pine) and Hevea brasiliensis (rubberwood) were degraded by brown-rot (Polyporus meliae) and white-rot (Trametes versicolor and Trametes hirsuta) fungi. The modification in the chemical structure of degraded wood was monitored by FTIR spectroscopy. In wood decayed by brown rot, there was a progressive increase in the lignin content, which is evident from increase in the relative intensities of lignin associated bands and a corresponding decrease in the intensities of carbohydrate bands. In contrast, there was a decrease in the lignin content of white rot decayed wood. Both the white rots used in this study showed preferential degradation of lignin, which is indicated by a reduction in relative intensities of lignin associated bands.     

磨木木素在硫酸盐法蒸煮过程中的反应

在木糖存在的条件下,采用硫酸盐法蒸煮的方法对蓝花楹磨木木素(milled wood lignin,简称MWL)进行处理,然后对处理后的产物进行红外光谱和13C-NMR分析,研究蓝花楹MWL的结构变化,探讨在硫酸盐法蒸煮过程中木素-碳水化合物复合体(lignin-carbohydrate complexes,简称LCC)的形成情况。研究发现:蓝花楹MWL结构单元之间的α-烷基芳基醚键、β-O-4型连接键很容易发生断裂,而在这些连接键发生断裂的同时,形成的木素中间体与糖产生化学键的结合,蒸煮液中有新的LCC结构形成。     

Analytical pyrolysis and FTIR spectroscopy of fossil Sequoiadendron giganteum (Lindl.) wood and MWLs isolated hereof

Recent and fossil woods from the genus of Sequoiadendron, as well as their milled wood lignins were investigated by means of FTIR spectroscopy and pyrolysis GC/MS technique. Though almost same in appearance the differences in band intensities of FTIR-spectra reveals the distinctly increased aromatic character and the oxidation in fossil specimens. More detailed information about the changes in old wood were obtained by analytical pyrolysis, which delivers degradation products with shortened side chains and more saturated units relating to fossil lignin.     

不同温度条件下木素模型物的热裂解产物的GC/MS研究

合成了一种β-O-4型木素模型化合物即愈创木基丙三醇-β-愈创木基醚,并利用红外光谱,核磁共振谱对其进行了分析和确认。在此基础上,研究了不同温度条件下(315℃~500℃)木素模型物的热裂解行为,利用GC/MS定性分析了裂解产物,讨论了部分产物与裂解温度之间的关系。实验结果表明:木素模型物在高温下(<400℃),裂解成愈创木酚、4-酰基愈创木酚等小分子的碎片,模型物裂解产物种类随温度的升高随之增多,但在更高的温度(>400℃),裂解的产物发生了聚合。     

烟草木质素结构的二维核磁共振波谱表征

[背景和目的]烟草木质素对烟草品质和安全性有重要影响,为了提高烟草制品的质量,需要探究烟草木质素的化学结构及含量.[方法]利用二维异核单量子相干核磁共振技术(2D HSQC NMR)建立表征烟草木质素的方法,实现烟草木质素的结构表征及半定量分析.[结果](1)烟草样品木质素中共发现10种主要的木质素基本单元及单元间连接...     

The impact of natural and artificial weathering on the visual,colour and structural changes of seven tropical woods

This study investigates the effects of wood weathering on changes in its macroscopic and colour characteristics in connection with changes in its molecular and anatomical structure. Seven hardwoods suitable for outdoor architecture—bangkirai, cumaru, cumaru rosa, ipé, jatobá, kusia, and massaranduba—were exposed to the exterior out of ground contact for 1–36 months according to EN 927-3, and for 1–12 weeks in Xenotest with water spraying according to partly modified EN 927-6. With prolonged weathering, the following changes occurred in the top surfaces of all tropical woods: (1) visual—creation of longitudinal macro-cracks, (2) spectrophotometry and CIE-L ^? a ^? b ^? —darkening in exterior exposure mainly due to pollutants, except for ipé, and vice versa lightening in Xenotest, as well as greening and blueing in both modes of exposure, (3) FTIR—faster decrease of guaiacyl than syringyl lignin, absolute decrease of conjugated and unconjugated carbonyl groups in the newly formed lignin-polysaccharide-extractive substrate in the photo-oxidized and washed-out cell walls, and decrease of cellulose crystallinity, (4) SEM—damaging of cell-walls by micro-cracks, and their degradation by thinning. Connections between changes of the individual characteristics of weathered woods, for example, between the colour (ΔE*, etc.) and the molecular structure (carbonyls, etc.), were also determined.     

Thermal studies of wood impregnated with ZnCl<Subscript>2</Subscript>

In this work the thermal behavior of wood impregnated with ZnCl₂ is studied. Impregnation of wood with ZnCl₂ is a treatment used in activated carbon production, and liquefaction and fast pyrolysis of biomass. Frequently, the impregnated wood is dried for several hours at temperatures above 370 K and then it is carbonized. Catalytic pyrolysis occurs, giving rise to a complex set of reactions. A TG/DTA study was done on the raw material, the activated carbon, the pure ZnCl₂ and the intermediate products in order to study the mass and thermal changes occurring. Elemental analysis and SEM analysis were also carried out. An exothermic torrefaction develops during the drying step; the torrefied product is carbonized in an endothermic process that involves ZnCl₂ volatilization. The washed impregnated wood carbonizes through an exothermic process that may involve the decomposition of cellulose, lignin and the solid product of hemicellulose torrefaction.     

Zum mikroskopischen Nachweis von Reaktionsholz (Druckholz) in thermo-mechanischem (TMP) und chemo-thermo-mechanischem Holzstoff (CTMP) der Fichte

Subject Compression wood can be qualitatively identified in thermo-mechanical and chemo-thermo-mechanical pulps by the colour reaction developed by Wiesner (1878) using an ethanolic solution of phloroglucinol (C₆H₃(OH)₃) acidified by hydrochloric acid. Compression wood cells appear dark red coloured in comparison to spring and summer wood cells. This is due to the relatively high lignin content in compression wood.      

Influence of fungal decay by different basidiomycetes on the structural integrity of Norway spruce wood

The potential influence of diverse decay patterns caused by different brown rot causing basidiomycetes on the structural integrity of wood was investigated. Therefore, decayed Norway spruce (Picea abies Karst.) specimens representing a wide range of mass loss, caused by four different brown-rot fungi and one white-rot fungus, were applied to a high-energy multiple impact (HEMI)-test series. The relationship between the resistance to impact milling (RIM) and the mass loss by fungal decay could be subdivided into three areas: 1. Prior to measurable mass loss, a strength reduction was detectable due to the depolymerisation of wood cell wall components. 2. Between 0 and 25–30% mass loss, RIM decreased with increasing mass loss. 3. Above 30% mass loss, RIM increased again due to gluing effects of the fungal mycelium. The influence of the different brown rot fungi on the structural integrity of the wood differed slightly, but partly significantly.     

Weathering characteristics of wood treated with water glass, siloxane or DMDHEU

Specimens of Scots pine sapwood (Pinus sylvestris) and beech wood (Fagus sylvatica) were treated with a sodium water glass solution, an amino-alkyl-functional oligomeric siloxane and 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU). The specimens were exposed outside without ground contact for 24 months. Colour measurements during outside exposure showed a discoloration of all wood specimen surfaces. FTIR spectroscopy displayed lignin degradation of all specimens during the initial exposure time. Chemical treatments decelerated fungal infestation of wood, while their effect on lignin degradation was not discernible. SEM studies revealed that fungal infestation was affected by the different treatments. The untreated specimens showed radial penetration of fungal hyphae through the pits. Only superficial infestation and no radial penetration were visible at water glass and siloxane treated specimens. A significantly reduced radial penetration of fungal hyphae was exhibited at DMDHEU treated specimens. Fungal infestation through the pits was not visible.     

Analysis of lignin from oak casks used for the maturation of Scotch whisky

Wood from four types of casks used for the maturation of Scotch whisky was analysed for free vanillin, syringaldehyde, vanillic and syringic acids and for milled wood lignin. Degradation of wood lignin by acidolysis was used to estimate the proportion of intact β-aryl ether linkages present. The yield of milled wood lignin was unaffected by repeated cask use. A comparison of acidolysis yields and the analysis of spirit matured for 3 years in each of the four types of cask indicated that the majority of β-aryl ether linkages in oak lignin are resistant to spirit hydrolysis and that cask exhaustion was not accompanied by significant delignification. Significant reductions in the concentrations of free guaiacyl and syringyl compounds were recorded for used casks and proved the best indicator of cask exhaustion.     

Light microscopic analysis of Tectona grandis L.f. wood inoculated with Irpex lacteus and Phanerochaete chrysosporium

Felling of immature teak (Tectona grandis L.f.) trees or delay in transport of wood logs from felling sites provide platform to microbial attack. Among them, white rot fungi are central driving force that degrades wood and causes severe economic loss. In contrast, Phanerochaete chrysosporium and Irpex lacteus are more extensively studied for their ability to degrade synthetic dyes and poly-aromatic compounds. Therefore, in the present study, both the fungi collected from the Gujarat forest were utilised for in vitro decay test to assess their potential in lignin degradation, extent of cell wall damage and pattern of wood decay in sound blocks of teak. In the early stage of fungal inoculation, there was a negligible amount of weight loss; after 1 month it became rapid and highest weight loss (30.05 % by P. chrysosporium and 27.97 % by I. lacteus) was observed at the end of 120 days. Mycelial invasion occurred through vessels, from vessels to axial and ray parenchyma and subsequently into xylem fibres. Both the strains showed selective delignification and the first symptom of degradation was defibration, separation of rays, and formation of boreholes on ray cell walls at an advanced stage. Xylem fibres and parenchyma cells lost their integrity and collapsed completely. Among all the cell types, parenchyma cells and fibres were more vulnerable to fungal attack, while vessels were resistant to the activity of lignolytic enzymes.     

漆酶/天然介体体系漂白硫酸盐竹浆的机理研究

对硫酸盐竹浆包含漆酶/天然介体漂白段的全无氯(TCF)漂白各段的残余木素进行了GPC、TGA、FT-IR、1H-NMR和t3C-NMR分析,主要探讨漆酶/天然介体体系(LMS)漂白的机理.分析表明,随漂白的进行,竹浆残余木素的总体变化趋势为分子质量降低;经LMS处理后,竹浆残余木素的热稳定性变差,更易在较低温度下热解;竹浆木素为GSH型,结构单元以G为主,苯丙烷单元之间的连接以β-O-4′为主,此外还有β-1′和β-5′连接.原浆木素中的羟基以酚羟基为主,苯丙烷单元中S的含量(以物质的量计,下同)少于1/3;O段残余木素中,脂肪族羟基比酚羟基多,且有少量-COOH、-OCH3被脱除,苯丙烷单元中G＞H＞S;LMS段残余木素中的羟基以脂肪族羟基为主,S单元含量增加,H单元含量减少,争1′连接增加,β-5′连接很少.     

Effects of silver nanoparticles and fungal degradation on density and chemical composition of heat-treated poplar wood (Populous euroamerica)

Effects of silver nanoparticles and fungal degradation on the weight loss and chemical composition of heat-treated poplar wood were studied. Wood blocks were impregnated with a 400 ppm nanosilver suspension under 3 bar pressure for 20 min using Lowry process (edited empty cell). Heat-treatment was carried out at 135, 160 and 185 °C. Specimens were divided into 4 groups; control, nanosilver impregnated, heat-treated and impregnated- heat treated specimens (135, 160 and 185 °C). All samples from the internal and superficial parts of the blocks were exposed to the white rot fungus Trametes versicolor. The results of heat-treated samples indicated higher amount of Klason lignin and extractives, but lower holocellulose and cellulose content. Furthermore, heat-treatment illustrated an increasing effect on the fungal resistance. For all the properties, significant difference was found between the internal and superficial test specimens. Nanosilver impregnation had an intensifying effect on the results of the heat-treatment.     

Effect of some metal nanoparticles on the spectroscopy analysis of Paulownia wood exposed to white-rot fungus

The present study was conducted to investigate the effects of impregnation with silver, copper, and zinc oxide aqueous nanofluids on the chemical properties of Paulownia fortunei decayed with the white-rot fungus Trametes versicolor. Wood specimens with a dry density of 0.37 g/cm³ were impregnated with a 400 ppm aqueous suspension of nanoparticles in a pressure vessel under 2.5 bars for 20 min. Specimens were inoculated with the fungus and incubated for 16 weeks at 26 °C and 65 % relative humidity in accordance with EN113. The spectra of specimens impregnated with nanosilver, nanocopper, or nanozinc-oxide showed no significant changes in their relative peak intensities of lignin and carbohydrates after exposure to T. versicolor. This can indicate fungicide effects of the metal nanoparticles on T. versicolor.     

Effect of heat treatment intensity on wood chemical composition and decay durability of Pinus patula

Heat treatment is an effective method to improve biological resistance of low natural durability wood species. The aim of this study was to enhance the decay resistance of Pinus patula, an African low natural durability softwood species, via wood thermal modification technique. Heat treatment was performed on wood specimens under inert conditions at different heat treatment intensities to reach mass losses of 5, 10 and 15%. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta. The wood chemical and elemental composition was determined as well as extractives toxicity before and after wood thermal modification to understand the reasons of durability improvement. The treated specimens exhibited a significant increase in their durability against wood decay in line with the severity of the treatment. Wood holocellulose was found to be distinctly more sensitive to the heating process than the lignin constituent. In addition, obvious correlations were observed between weight losses recorded after fungal exposure and both holocellulose decrease and lignin ratio increase. The same correlations were observed with the elemental composition changes allowing using the observed differences for predicting of wood durability conferred by heat treatment. Furthermore, no significant differences were observed between the toxicity of Pinus patula wood extractives before and after its thermal modification.     

Über das Sorptionsverhalten wärmebehandelter Hölzer

Summary The heating of solid wood to higher temperatures is the simplest and cheapest means for stabilizing its dimensions. Caused by the partial thermal degradation of the chemical components of the wood occurring in heat stabilization, also other physical properties are considerably changed. For the investigation of the effect of thermal treatment on the sorption of the wood, oven-dry samples of beech-wood, vakwood, and pine sapwood were heated in presence of air at temperatures of 70°–200°C for different periods (6, 24, and 48 hours). Subsequently, for these samples the adsorption and desorption isotherms were taken up at 20°C in a vacuum-sorption apparatus, and there from the avarage sorption of the woods was determined. When heated at 70°C the sorption capacity of the three woods was not changed. The thermal treatments at 100°, 130°, and 150°C resulted in a decrease in the sorption capacity, being the greater the higher the temperature and the longer the time of heating were. The heating-treatments of 6 and 24 hours at 180°C yielded, in an equal sense, even greater decreases in the sorption capacity, though after 48 hours of heating the decrease was less than after 24 hours. During the interval of 24 to 48 hours at 180°C, consequently chemical processes must have taken place in the woods now resulting in a rise of the sorption capacity. This should have been caused by the sampleting of the lignin. The determined changes in the sorption of the heat-treated woods are explained by the sorption behaviour of the chemical wood components cellulose, wood polyoses, and lignin and their proportions in the chemical composition of the wood as well as their different thermal stability.

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Mitteilung aus dem Institut für Holzforschung und Holztechnik der Universit?t München     

The chemistry of Kielmeyera coriacea outer bark: a potential source for cork

Cork is a material with a wide array of properties that make it uniquely suitable for many technological applications. All industrial cork comes from a single tree species, the cork-oak (Quercus suber L.), which is limited to the western Mediterranean region. A number of other trees and shrubs with “corky barks” are found in savannah-type ecosystems, namely in the Brazilian “Cerrado”, of which Kielmeyera coriacea Mart. and Zucc. (Pau-santo) is a conspicuous example. In this work, the chemical composition of K. coriacea outer bark as well as its extractives and suberin composition were analysed from the perspective of its potential use as an industrial cork source. K. coriacea outer bark showed a fairly high extractives content, ~15–20 %, with a significant proportion (6–10 %) of non-polar compounds, including very long chain (>C₂₈) fatty acids (28 % of the dichloromethane extract) and xanthones (19 %). The suberin content varied from 17 to 30 %, total lignin from 44 to 55 % and the polysaccharides from 11 to 17 %, showing less suberin and polysaccharides and more lignin than the reference Q. suber cork. K. coriacea cork suberin composition was dominated by C₁₈ mid-chain substituted ω-hydroxyacids and α,ω-diacids, with a noticeable absence of saturated chain monomers. Taking into account its cork content together with its cellular structure and chemical composition, K. coriacea outer bark is a potential source for cork. Although it might not be appropriate for solid cork products, it can be used to produce granulated cork for composite materials, or as a source of suberin-derived bio-based chemicals.     

An investigation of thermochemical changes in Canadian hardwood species during wood welding

Thermochemical changes during wood-dowel welding were investigated in two Canadian hardwood species commonly used for indoor appearance applications: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). The original reference wood sample and the welded interface between two bonded wood pieces, a dowel and a substrate, were compared to explain differences in mechanical properties between species. Pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used. The gases emitted during wood welding were determined by Py-GC/MS and gas chromatography coupled with a thermal conductivity detector and a flame ionization detector (GC-TCD/FID). Results showed that thermal welding of birch and maple woods degrades hemicelluloses and affects lignin polymer through depolymerisation. Welding effectiveness is therefore directly associated with the properties of the original wood constituents, primarily lignin and carbohydrates. The lignin-related changes at the welded interface were greater for sugar maple than for yellow birch, corroborating mechanical property differences observed between the two species. The gases proportions were similar for both species and no harmful gases were detected in the smoke released during welding process.     

Effect of <Emphasis Type="Italic">Punica granatum</Emphasis> peel and <Emphasis Type="Italic">Melia azedarach</Emphasis> bark extracts on durability of European beech and maritime pine

A method to improve wood durability using natural extracts was evaluated. Wood deterioration is a condition caused by several abiotic and biotic factors including fungal contamination. To date, approaches aiming at the reduction of these contaminants mainly involve the use of chemicals agents. Natural products could represent an alternative strategy. Aqueous extracts of Punica granatum L. (pomegranate) peel and Melia azedarach L. barks were evaluated as antifungal agents to improve natural durability of beech wood and maritime pine. To evaluate the effect of treatments under simulated accelerated ageing of wood by natural conditions, impregnation and leaching tests were performed. Results demonstrated that samples impregnated with pomegranate or M. azedarach solutions notably increased the biological resistance of wood in a dose-dependent manner. These results were confirmed by the reduction in weight losses in treated samples even after 6 weeks of fungal exposure. Moreover, after leaching tests, 20 and 7% (w/v) of pomegranate and M. azedarach extract solutions were demonstrated as the better concentrations to enhance wood durability. Total phenol content and characterization of the phenolic compounds in both, natural extracts and wood samples were analyzed by Folin–Ciocalteu assay and HPLC-DAD. In conclusion, it was demonstrated that the present method can be considered as an effective treatment to increase wood durability while it proposes the valorization of natural extractives in wood industry.