The comparison of chemical and structural differences of Caribean pine (Pinus caribea L.) wood and bark lignin

The presented paper deals with some chemical properties of Caribean pine wood and bark lignin. In order to obtain necessary data, the following operations and analyses were performed: dioxane lignin isolations, determination of Klason lignin, determination of methoxyl, carboxyl and phenolic hydroxyl groups in dioxane lignins and the nitrobenzene oxidation of both compared lignins and of the risidues remaining after dioxane lignins extraction. The oxidation products were analysed by GLC. The experimental data show that there are moderate differences between compared lignins.     

A comparative study of hard and softwood lignins alterations during treatment in dioxane-water-HCl agent

The objective of the presented contribution was a study of the lignin alterations occurring in the process of the acidolytic delignification of chosen representatives of soft and hard wood species (maple and spruce) in dioxane-water-HCl mixture. All lignin samples were characterised by yield or recovery, molecular weights, as well as by GLC data of corresponding nitrobenzene oxidation products. In order to obtain more information about condensation and degradative reactions of lignin under conditions of acidolytic treatment a simulation of the process of lignin isolation was performed, too. Samples of dioxane lignins obtained after 90 min. of isolation at 82.5 and 98 °C were therefore recooked during 360 min. under identical conditions as applied in the lignin isolations. Concentrations of lignin in the reaction mixture were 1 and 10% thus approximately corresponding the lignin concentration inside and outside of the wood meal during the lignin isolation. The obtained experimental data point out the course of both degradative and condensation reactions. Maple wood lignin undergo deeper degradation than those of spruce under the same reaction conditions. The decreased yields of lignin oxidation products with the time of acidolytic treatment and after recooking hint at the formation of new linkages among building units of lignin thus modifying its macromolecules. The intensity of occurring alterations of examined lignins is not only dependent of time and temperature, but also of the concentration of lignin.     

Chemisch-analytische Untersuchungen am Holz erkrankter Bäume

The results of two research series are described. In the first series the alkali extracts of spruce and pine wood from three sites each have been studied. There are no differences within the natural deviation range between wood of sound and declining trees regarding the percentages of the alkali extracts as well as the amount of soluble polysaccharides and soluble lignin. The second series of deals with the lignin soluble in dioxane in various annual ring ranges of spruces and firs from one site. Also in this series no change of the solubility of lignin depending on the loss of needles was found. The characteristics of the dioxane extracts realized by infra-red spectroscopy are the same for all samples. Spruces and pines show, however, an increase of the solubility of lignin in the heartwood compared with the sapwood.     

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.     

Characterization of asparagus lignin by HPLC

Lignin is the cell wall component most frequently associated with hardening. Its characterization and quantification are very important to understand the biochemical modifications related to the changes in texture of vegetables such as asparagus (Asparagus officinalis), in which this organoleptic attribute is a very important quality factor. In this study, asparagus lignin from the basal sections of fresh and stored spears was analyzed using 2 methods, the traditional (Klason lignin) and the recently developed derivatization, followed by reductive cleavage (DFRC) method. The latter is a simple and reproducible technique for lignin characterization based on a degradation procedure that produces analyzable monomers and dimers by cleaving alpha- and beta-aryl ethers in lignins. The primary monomers derived from DFRC degradation of lignins are essentially p-coumaryl peracetate, coniferyl peracetate, and sinapyl peracetate. To evaluate the efficiency of the DFRC method, our investigations have been carried on distinct sample types, including wood (data not shown), straw, and asparagus samples. The results have confirmed that lignin composition is affected by plant nature. It has been found that whereas wood samples mostly contain coniferyl units, plant foods, such as straw and asparagus, contain both coniferyl and guaiacyl units.     

Ethanol extractives of fossil Sequoia wood

Except for small amounts of neutral compounds, the ethanol extracts from fossil Sequoia wood contained over 80% polymeric substances. The bulk of materials was separated into fractions by column chromatography and investigated by means of UV- and FTIR spectroscopy. According to the results the polymeric products are a type of Brauns lignins. Both spectroscopic data revealed considerable changes in. composition and constitution of lignin.     

Comparative characterisation of dioxane-soluble lignins released by ball milling and by sheep digestion from forage grasses

Faecal soluble lignin (FSL), extracted from the faeces of sheep that received orchardgrass and timothy, were compared with 90% dioxane-soluble lignins released by ball milling (MHL) and by subsequent enzymatic hydrolysis (EHL) from the same grasses. FSL contained much less carbohydrate and esterified p-coumaric and ferulic acids than MHL and EHL. Although no considerable differences were found in the yields of vanillin and syringaldehyde produced by nitrobenzene oxidation, the molar ratio of syringaldehyde to vanillin was higher for FSL than for MHL and EHL. Such differences in chemical properties among the lignin preparations were confirmed by ¹³C-NMR spectroscopy. FSL had a lower molecular size compared with MHL and EHL. Results indicated that syringyl-rich lignin fragments with less phenolic acid esters, probably depolymerisation products of the grass lignins, were released by digestion in sheep from the forage grasses.     

Changes on Content,Structure and Surface Distribution of Lignin in Jute Fibers After Laccase Treatment

Effect of laccase treatment on the content, structure, and surface distribution of lignin in jute fibers were fundamentally investigated. Four percent lignin was removed from jute fibers via the laccase treatment. The residual lignin in the laccase-treated jute fibers showed increased molecular weights, which indicated polymerization between lignins on jute fibers. Meanwhile, the phenolic hydroxyl content in lignin decreased during the laccase oxidation accompanied by demethylation of methoxyl groups and generation of carbonyl groups. Due to the degradation and subsequent polymerization of lignin by laccase, the bulgy lignins on jute fiber surfaces were redistributed, which made the surface neat and glossy.     

Bestimmung der phenolischen Hydroxylgruppen in Ligninen und Ligninfraktionen durch Aminolyse und FTIR-Spektroskopie

The quantitative analysis of phenolic OH groups is of interest for the characterization of isolated lignins when evaluating the extent to which lignin has been changed. While aminolysis is a very accurate if elaborate chemical method, the evaluation of the aliphatic and aromatic IR ester bands of acetylated lignins at 1745 and 1765 cm^?1 permits a quick, easy and reliable determination of the phenolic hydroxyl groups. The excellent correlation between the two methods was proved for 35 different lignins and lignin fractions of different molecular weights.     

Orientierende Untersuchungen zum Organosolv-Aufschluß von Buchenholz mit einem Propandiol/Wasser-Gemisch

Beech wood (Fagus sylvatica L.) was digested in organosolv processes using ethanol/water (EtOH/H₂O) and propandiol-(1,2)/water (PDO/H₂O). The pulping qualities of both agents were compred. The pulp yield is lower for PDO/H₂O than for EtOH/H₂O. While almost the whole lignin can be recovered in a simple manner from the EtOH spent cooking liquor, the lignin from the PDO-liquors can only be partly isolated. Due to its high boiling point the recovery of PDO from the spent pulping liquors is more difficult than that of EtOH. Schemes of the recovery of pulps and lignins as well as lignin and carbohydrate balances demonstrate the results of the pulping experiments.     

Modification of beech veneers with lignin phenol formaldehyde resins in the production of laminated veneer lumber (LVL)

Rotary cut beech (Fagus sylvatica L.) veneers were treated with four different lignin phenol formaldehyde (LPF) solutions using dimethyl sulfoxide (DMSO) as a solvent. Four of these veneers were bonded with PF adhesive to produce four-layer laminated veneer lumber (LVL). To synthesize the LPF solutions, a commercial phenol formaldehyde resin (PF resin) was individually mixed with three different technical lignins (Indulin AT, BioChoice lignin, organosolv lignin) and lignin cleavage products (LCP) at a ratio of 3:2 (60%:40%). Differential scanning calorimetry showed an increased curing temperature for the LPF resins in comparison to the PF resin. The mechanical and water-related properties of the LPF-modified LVL were shown to be similar or slightly improved compared to PF-modified LVL. Fungal degradation experiments with white-rot fungus (Trametes versicolor) and brown-rot fungus (Coniophora puteana) exhibited no significant differences in the mass loss of the LPF-modified and PF-modified samples except in one case: LVL made from veneers treated with Indulin AT exposed to the white-rot fungus. The resistance to weathering of LVL samples made from veneers treated with technical lignins was low; however, specimens treated with LCP and the reference PF resin displayed a higher resistance to weathering. It is concluded that technical lignins or LCP can, to a certain extent, be used as a substitute for crude-oil based PF resin.     

An investigation of lignin extraction from dietary fibre using acetyl bromide

Acetyl bromide is a suitable reagent for the extraction of lignins from woody material and grasses but lignins present in vegetables do not give the expected absorbance spectrum. Treatment of the vegetable fibre with either organic solvents or dilute acid or the removal of protein and hemicellulose does not alter the absorbance spectrum of lignins present in vegetables. All methods used for lignin extraction are quantitatively consistent and show only a trace of lignin to be present in vegetable fibre.     

Biological variability in lignification of maize: Expression of the brown midrib bm2 mutation

The cell wall phenolic components in the internodes of three maize genotypes, namely normal, bm2 and bm3 maize, were determined. The bm2 and bm3 brown midrib mutations lowered the lignin content of the bottom, middle and top internodes to a similar extent. However, unlike bm3, the bm2 trait did not induce a sharp reduction of the level of ester-bound p-coumaric acid in maize internodes. The other main alkali labile phenolic acid, ferulic acid, reached similar levels in the three genotypes. The main difference between bm2 and bm3 mutations occurred in the alkyl aryl ether linked structures of the lignin component. In contrast to bm3 lignins, which are characterised by a low syringyl content, the bm2 lignin had a lower content of guaiacyl units than lignin of normal maize internode. Consequently, the syringyl/guaiacyl molar ratio of bm2 lignin gave higher values (2.7–3.2) than those from either normal (0.9–1.5) or bm3 lignins (0.3). The alkali solubility of lignin was also compared between the three genotypes. Incorporation of the bm3 trait in maize led to a high recovery of alkali soluble lignin whereas the bm2 lignin had a similar solubility to the normal one in 2 M NaOH. The monomeric composition of the alkali soluble lignins was consistent with the non-condensed structures of the in-situ polymer. Although the bm3 and bm2 mutations had different effects on lignification, the modification of the cell wall phenolic level was also found in the bm2 maize stem as previously studied.     

造纸黑液中碱木素的提取及其在石化工业中的应用

主要介绍了碱木素的提取,碱木素的结构特性和反应性能。详细阐述了碱木素在石化工业中的应用及其它应用前景。     

Characterization of trembling aspen wood (Populus tremuloides L.) degraded with the white rot fungus Ceriporiopsis subvermispora and MWLs isolated thereof

Trembling aspen wood (Populus tremuloides L.) was treated with white rot fungus Ceriporiopsis subvermispora for 1, 2, 4, and 6 weeks. As fungal decay advanced, lignin contents were decreased gradually up to ca. 27.5% (based on the Klason residues of the control) after 6 weeks. Alkali solubility of cell wall residues was increased until 4 weeks of fungal treatment, but additional treatment did not cause any effects. Milled wood lignins (MWLs) were isolated from the decayed woods by Björkman’s procedure and subjected to thioacidolysis and analytical pyrolysis to investigate the modification of lignin structures during fungal degradation. Thioacidolysis revealed that the yields of trithioethylated C₆C₃ monomers, as a parameter for frequency of β-O-4 linkages in lignin, were substantially reduced (-20%, based on the control) in MWLs isolated from decayed woods. Analytical pyrolysis revealed that the relative amounts of coniferyl alcohol and sinapyl alcohol in the pyrolysates were lowered dependent on the biodegradation time, whereas an elevation of C₆C₁ and C₆C₂ pyrolytic phenols was observed. The results from both analytical methods strongly suggested that β-O-4 linkages were cleaved by C. subvermispora. Specially, degradation of syringyl-type lignin seems to be preferred.     

14C labelling of lignins of normal and bm3 maizes for fermentation studies

[U-¹⁴C] phenylalanine (phe*) and [O¹⁴CH₃] sinapic acid (sin*) were infused into the cut ends of normal and bm3 maizes (anthesis stage) under or above the last node or at mid-internode, with or without the leaf, in light or in darkness. Radioactivity was measured in the organs, and in phenolic constituents of the cell wall and saponified residues of the bases and tops of the apical inter-node. In both maize genotype labelled under the node the radioactivity was distributed more evenly in the organs with sin* than with phe*. Infusion above the node and at mid-internode greatly increased radioactivity in the bases and tops, respectively. Removal of the leaf only slightly increased the radioactivity, mainly in the bases, and no clear-cut effect of darkness was observed. Phe* labelled the phenolic acids and the three lignin units, but the syringyl units of bm3 maize were only slightly labelled. Sin* specifically labelled the syringyl units, which represented the least condensed fraction of lignins. Both the native and labelled lignins were highly alkali soluble. There were differences in lignin biogenesis between the bases and tops, and between normal and bm3 maizes. The newly formed lignins were slightly different from the native lignins but had similar types of heterogeneity, with variations in the internode and between genotypes similar to those in native lignins. Provided due allowance is made for the distinguishing characteristics of newly formed lignins, the [¹⁴C-lignin] cell walls, which are strongly labelled on complementary structures, seem suitable model substrates for fermentation studies.     

传统熏烤木材中木质素结构表征及其热解特性

为探究传统熏烤肉制品熏烤时所采用不同化学组成及结构的木材类型对产生有害物质多环芳烃的种类和生成量的影响,以传统熏烤肉制品生产时常用的松木、杨木、榉木、枣木、苹果木5种木材为研究对象,通过红外光谱、拉曼光谱、热重及热重-红外联用分析,考察5种木材中木质素的结构特征及其热解特性。结果表明：5种木材中木质素含量,以及木质素中愈创木基结构单元（G）、紫丁香基结构单元（S）含量均存在差异;热解过程基本可分为3个阶段,主要发生在200～500℃范围内,但是5种木质素的质量损失速率、质量损失温度、热解速率、热解温度均不同,说明不同木质素的热稳定性存在显著差异。熏烤木材中木质素含量,S/G结构含量及侧链结构上差异可导致其热稳定性的不同,而热解特性的不同则进一步影响多环芳烃等有害物的生成。     

Pyrolytic and hydrogenolytic degradation studies on lignocellulosics,pulps and lignins

Wood and MWL's from beech, spruce, bamboo as well as teak wood and teak-HCl-lignin were subjected to analytical pyrolysis (Py), using the off-line approach, and to hydrogenolysis (Hy). Gas chromatography-mass spectrometry (GCMS) was used for product identification and assignment as derivatives from 4-hydroxy-phenyl-propane, guaiacylpropane and syringylpropane basic units followed by capillary gas chromatography (GC) for quantitative determination of the phenolics. The results are compared with those of nitrobenzene oxidation and quantitative FTIR-spectroscopy. Py-GC and Hy-GC experiments were also used for the characterization of residual lignins in kraft and alkaline-sulphite-anthraquinone-methanol (ASAM) pulps from beech, pine and sugar cane bagasse. Analytical pyrolysis of biomass, both in on-line and off-line approach, is well suitable for lignin classification even without previous lignin isolation. Hydrogenolysis is more recommendable for the characterization of residual lignins in pulps.     

Chemical and in vivo evaluation of a brown midrib mutant of Zea mays. II. Nuclear magnetic resonance spectra of digested and undigested alkali lignins and undigested dimethyformamide lignins

Nuclear magnetic resonance (n.m.r.) spectra were obtained on the alkali lignins extracted from Tr and bm₁ cornstalks, before and after digestion by sheep, and on the dimethylformamide lignins (DMFL) from undigested cornstalks. Differences due to solvent extraction, plant genotype and digestion were apparent. The bm¹ corn lignin has a higher degree of cross linking of the propane side chain of the lignin molecule than Tr corn lignin, a factor which may be significant in determining the effect of lignin on digestibility. The main effect of digestion was to increase the degree of cross-linking of the propane side chain, especially with the Tr lignin. Alkali lignin n.m.r. spectra were considerably different from DMFL n.m.r. spectra. For example over 40% of the total bm DMFL protons were highly shielded protons but these were virtually absent in the alkali lignins. These highly shielded protons cannot be explained by the presence of ferulic and p-coumaric acids in DMFL.     

三倍体毛白杨不同制浆方法浆中残留木素结构的变化

用硝基苯氧化法分析了三倍体毛白杨的木素单元结构,并对三倍体毛白杨进行了硫酸盐法和碱性亚钠-蒽醌法制浆,提取了两种未漂浆的浆中残留木素,用红外光谱和13C-NMR详细分析了其结构,研究结果表明:和普通毛白杨相此,三倍体毛白杨木素缩合型结构的比例较高;和硫酸盐法制浆相比,碱性亚钠-蒽醌法制得的浆中含有较少的木素缩合结构和木素-碳水化合物复合体(LCC),羧基含量较低。这些研究结果为进一步研究三倍体毛白杨浆漂白性能打下基础。