Institut für Holztechnologie Dresden

Results of a comprehensive study on the chemical structure of lignin from plantation Eucalyptus globulus Labill are presented. Lignin has been isolated by a modified mild acidolysis method and thoroughly characterized by functional group analysis, by a series of degradation techniques (nitrobenzene oxidation, permanganate oxidation, thioacidolysis, and Py-GC-MS), and (1)H and (13)C NMR spectroscopy. Plantation Eucalyptus globulus lignin was found to be of the S/G type with an extremely high proportion of syringyl (S) units (82-86%) and a minor proportion of p-hydrophenyl propane (H) units (roughly 2-3 mol %). Unknown C-6 substituted and 4-O-5' type syringyl substructures represent about 65% of lignin "condensed" structures. Eucalypt lignin showed high abundance of beta-O-4 (0.56/C(6)) structures and units linked by alpha-O-4 bonds (0.23/C(6)). The proportion of phenylcoumaran structures was relatively low (0.03/C(6)). Different kinds of beta-beta substructures (pino-/syringaresinol and isotaxiresinol types) in a total amount of 0.13/C(6) were detected. ESI-MS analysis revealed a wide molecular weight distribution of lignin with the center of gravity of mass distribution around 2500 u.

This report describes ways in which the properties of wood might be improved by application of silica and other inorganic nanosols. Topics covered are: the synthesis and modification of inorganic nanosols, and methods of applying them to wood to improve its mechanical properties; the use of modified silica sols to realise flame retardant, water repellent and antimicrobial properties; recent nanosol applications for protecting ThermoWood, for restoring and preserving wooden cultural artefacts, and as auxiliaries for improving commercial wood lacquers.

A critical review of bark anatomical terms is undertaken to stimulate the discussion on bark terminology. Suggestions are made for a standardised usage of the corresponding terms for facilitating the communication between people working on bark anatomy. A tentative glossary of terms is given at the end of the paper.

PURPOSE: Many studies have shown that local anesthetics may impede chondrocyte metabolism. However, the influence of a single-dose local anesthetics is controversial. The aim of this metaanalysis was to review the literature for studies investigating the cytotoxic effects of single-dose local anesthetics on chondrocytes and cartilage. METHODS: A comprehensive literature search was performed using established search engines (Medline, Embase) to identify studies, investigating the influence of single-dose local anesthetics on cartilage. The systematic analysis included the influence on histology, cell viability, morphology, and matrix production depending upon dose, exposure time, and type of local anesthetics. RESULTS: Twelve studies with four different local anesthetics were included in this metaanalysis. Bupivacaine and lidocaine were found to be more chondrotoxic than mepivacaine and ropivacaine. The amount of dead cells increased in a substance-, dose-, and time-dependent process. Osteoarthritic cartilage seems to be more vulnerable compared to intact cartilage. The toxic effects occur first in the superficial cartilage layers and include damage to membrane integrity, mitochondrial DNA, and nuclear changes. There is no study that could show a significant chondrotoxic effect with low concentrations of bupivacaine (0.0625%), ropivacaine (0.1 and 0.2%), and mepivacaine (0.5%). CONCLUSIONS: The cytotoxicity of local anesthetics on chondrocytes is dependent on dose, time, and type of local anesthetics. Single-dose intra-articular administration of local anesthetics impede chondrocyte metabolism and should be performed only with low concentrations for selected diagnostic purposes and painful joints. The use of lidocaine should be avoided. LEVEL OF EVIDENCE: II.

Smoke flavourings are produced on a large scale and have been applied to a variety of food products for more than 30 years. The use of them has many advantages compared to traditional smoking techniques. Among others, the amount of (known) toxic compounds deriving from combustion processes can be more easily controlled in smoke flavourings. In order to ensure safe products, a new European Regulation requests data on the composition and lays down, in particular, the maximum permitted concentrations for selected polycyclic aromatic hydrocarbons (PAHs). This review compiles results published on the chemical composition of liquid smoke flavouring primary products, partly in relation to production process parameters, and the analytical methods involved. The methods cover chromatographic techniques for analysis of specific compounds including extraction methods and clean-up procedures. Analysis of sensorial and bulk parameters such as acidity and total phenolic compounds are described as well as they are used as standard methods for analysis of liquid smoke flavourings. A special section is devoted to discussing the analysis of PAHs.

Wood-plastic composites from bio-based polymers and wood fibers (bio-WPC) provide an improved sustainability and carbon footprint compared to conventional composites. Actually, the implementation of this approach into industrial applications is hindered by the missing knowledge on the mechanical and thermo-mechanical properties of such bio-WPC. In this study, the properties of a bio-WPC from bio-based polyamide 11 (PA 11) and chemically modified beech fibers were investigated. The chemical modification of the beech fibers by an alkaline treatment with an aqueous solution of sodium hydroxide (NaOH) was done to support the melt processing and adhesion to the PA 11 matrix. Analysis of the modified fibers by Thermogravimetric Analysis (TGA) proved an increased thermal stability, as identified by an increase of the extrapolated TGA onset temperature from 290 to 330 °C. This improvement resulted from hemicellulose removal, as confirmed through Attenuated Total Reflection Infrared Spectroscopy (ATR-FTIR). Consequently, mechanical and thermo-mechanical analysis of the processed bio-WPC showed an increase in elastic modulus and storage modulus of the composites by the chemical treatment of the fibers. This effect was attributed to an increased number of hydrogen bonds between the modified beech fibers and the PA 11 matrix. The overall mechanical properties of the investigated bio-WPCs support their use as sustainable construction material for technical applications.

Talaromyces emersonii, a thermophilic aerobic fungus, produces a complete xylan-degrading enzyme system when grown on appropriate substrates. In this paper we present the physicochemical and catalytic properties of three enzymes, xylosidase (Xyl) I (M(r) 181,000; pI 8.9), II (M(r) 131,000; pI 5.3) and III (M(r) 54,200; pI 4.2). Xyl I and II appear to be dimeric and Xyl III is a single-subunit protein. All three enzymes catalyse the hydrolysis of aryl beta-D-xylosides and xylo-oligosaccharides. Xyl I is a classic beta-xylosidase (1,4-beta-D-xylan xylohydrolase; EC 3.2.1.37), and Xyl II and III are novel xylanases (endo-1,4-beta-D-xylan xylanohydrolase; EC 3.2.1.8) which we believe have not hitherto been reported. In addition to the above substrates, they also catalyse the extensive hydrolysis of unsubstituted xylans, and may have considerable biotechnological potential. The hydrolysis product profiles and bond-cleavage frequencies with various substrates are presented.

The axial variation of bark thickness and quantitative anatomical features of Eucalyptus globulus bark were analysed for one site based on individual measurements of ten 15-year-old trees at six height levels (DBH, 5%, 15%, 35%, 55% and 75% of total tree height). The parameters studied were: length, tangential diameter and percentage of sieve tubes; length, width, cell wall thickness and percentage of fibres; height and percentage of rays; percentage of sclereids in the secondary phloem. Bark thickness decreases from base to top of the tree. Fibre width and wall thickness decrease from base upwards. No distinct axial patterns of variation were observed for the other biometric variables studied. Parenchyma is the main cell type of the bark (50%) followed by fibres (27.9%), rays (12.1%), sieve tubes (2.7%), and sclereids (7.3%). The cell type proportions vary significantly within the tree, i.e., parenchyma, ray and sclereid proportions decrease, fibre and sieve tube proportions increase towards the top of the tree.

Highly swellable lignin derivatives were prepared by cross-linking of oxidatively preactivated spruce organosolv lignin (OSL) with poly(ethylene) glycol diglycidyl ether (PEGDGE). The lignin gels obtained are considered to be an environmentally friendly alternative to synthetic hydrogels and superabsorbents and represent a novel type of lignin based functional materials. For their application, it is not only the absorption of water in terms of hydrogel swelling that plays an important role, but also the adsorption and retention of moisture by the corresponding xerogels. To reveal the mechanisms involved in moistening and reswelling of the lignin gels, the interaction of water vapor with lyophilized xerogels was investigated and compared with sorption characteristics of parent lignin. The chemical structure of PEGDGE-modified lignin was investigated using attenuated total reflectance Fourier-transformed infrared spectroscopy and selective aminolysis and was related to its sorption and swelling characteristics. Bound and free water in hydrogels was determined by differential scanning calorimetry and by measuring the free swelling capacity of the gels. Moisture sorption of OSL and PEGDGE-modified lignin xerogels was determined using dynamic vapor sorption analysis. In order to determine monolayer and multilayer sorption parameters, sorption data were fitted to the Brunauer-Emmett-Teller and the Guggenheim-Anderson-de Boer model. Swelling properties of the hydrogels and moisture sorption of the corresponding xerogels were found to be strongly dependent on the degree of chemical modification with PEGDGE: Total and free water content of hydrogels decrease with increasing cross-linking density; on the other hand, water bound in hydrogels and moisture sorption of xerogels at high levels of water activity strongly increase, presumably because of the hydration of hydrophilic oligo(oxyethylene) and oligo(oxyethylene) glycol substituents, which lead to moisture diffusion into the xerogel matrix, plasticization, and swelling of the gels.

Four carboxymethyl cellulose samples derived from the synthesis concept of “reaction in reactive microstructures” were characterised in detail by combination of different analytical techniques. Fractionation of one of the samples according to water-solubility into four fractions revealed that a non-statistical distribution of the substituents occurred for all fractions. Endoglucanase fragmentation of three samples was performed followed by analytical and preparative SEC. The multi-detected analytical SEC proved samples of high degree of substitution up to 1.9 to be intensively degraded, supporting the proposed block-like substitution pattern. The detailed investigation of soluble fragmentation products by preparative SEC, hydrolysis and anion exchange chromatography with pulsed amperometric detection revealed that all samples contain fragments of much higher DS values than the average DS of the starting material. On the other hand, high quantities of degradation products of low DS or almost no substitution occurred. Therefore, a structure can be proposed with segments of very high DS alternating with areas of limited substitution. The result clearly showed that the high substituted fragments were dominated by 2,3,6-tri-O-CMG.

Abstract Fine structural studies on the needles of damaged fir (Abies alba Mill.) and spruce [Picea abics (L.) Karst.] trees from forest dieback areas in the Black Forest . The fine structural changes in the variously damaged needles of fir and spruce trees from forest dieback areas have been investigated with special reference to cytoplasmie organization in the vascular bundles, mesophyll tissue and cuticle. The results are compared with those available for a few plants affected both by natural and artificial stress factors, especially air pollutants.

Abstract Scanning electron microscopical investigations on stomatal wax plugs of fir and spruce needles after fumigation and acid rain treatment Alterations of stomatal wax plugs of fir and spruce needles have been investigated in order to demonstrate the effects of different air pollutants. After acid rain treatment, and in addition to SO 2 fumigation, heavily melted wax crystals were observed. It is assumed that acid rain causes mainly the changes of the stomatal wax plugs.

Abstract The following compounds were identified as male pheromone components of the longhorn beetles Hylotrupes bajulus and Pyrrhidium sanguineum : (3 R )‐3‐hydroxy‐2‐hexanone [(3 R )‐ 1 ], (2 S ,3 R )‐2,3‐hexanediol [(2 S ,3 R )‐ 4 ] and (2 R ,3 R )‐2,3‐hexanediol [(2 R ,3 R )‐ 4 ]. The syntheses of enantiomerically pure samples, enantiomeric separation by chiral gas chromatography and unambiguous structure assignment of the target compounds are described.

Two endo-fl-l,4-xylan xylanohydrolases (EC 3.2.1.8), XynA and XynB, from solid-state cultures of Penicillium eapsulatum, were purified to apparent homogeneity as judged by electrophoresis and isoelectric focusing. Each is a single subunit glycoprotein. XynA containing 97 mol carbohydrate.tool -1 protein, while XynB contains 63 mol.mol-~. M r and pI values are 28500, 5.0-5.2 (XynA) and 29500, 5.0-5.2 (XynB), respectively. Both enzymes are most active at pH 4 and 47-48 ~ and have half-lives of 32 rain (XynA) and 13 rain (XynB) at pH 4, 60 ~ Each form catalyzed the hydrolysis of a variety of xylans, albeit with different degrees of efficiency. In addition, XynB catalyzed extensive degradation of barley fl-glucan, CM-cellulose and, to a lesser extent, lichenan, but kinetic parameters indicate that it is primarily a xylanase. The products of hydrolysis of various xylans and xylopentaose differed for each enzyme and ranged from xylose to xyloheptaose depending on the substrate used. Each enzyme is endo-acting and has transferase as well as direct hydrolase activity. Inactivation by N-bromosuccinimide indicated the possible involvement of tryptophan in binding and/or catalysis.

A xylan-degrading enzyme (xylanase II) was purified to apparent homogeneity from solid-state cultures of Aspergillus fumigatus Fresenius. The molecular weight of xylanase II was found to be 19 and 8.5 kDa, as estimated by SDS-PAGE and gel filtration on FPLC, respectively. The purified enzyme was most active at 55 °C and pH 5.5. It was specific to xylan. The apparent Km and Vmax values on soluble and insoluble xylans from oat spelt and birchwood showed that xylanase II was most active on soluble birchwood xylan. Studies on hydrolysis products of various xylans and xylooligomers by xylanase II on HPLC showed that the enzyme released a range of products from xylobiose to xylohexaose, with a small amount of xylose from xylooligomers, and presented transferase activity.

Since cross-linked hydrogels from oxyethylated lignins (OELs) are progressively more regarded as water-retaining soil improvements based on sustainable and biorenewable resources, an effort is made here to gain some insight into the biodegradation behavior of these materials. For this purpose, model soils with defined sand/lignin and sand/OEL ratios were incubated in a closed system under laboratory conditions, and carbon dioxide evolved by microbial lignin and OEL decomposition was determined. OELs with different oxyethylation/cross-linking degrees and water absorption capacities were included into the experiments and compared with respective types of parent technical soft wood and hard wood lignins. The results suggest a medium- to long-term biodegradability of OELs ensuring a long-term functionality of the hydrogel materials on the one hand and a subsequent integration of respective degradation products into the natural carbon cycles on the other hand. It was found that the short-term carbon mineralization rates of OELs are markedly lower compared to that of parent lignins and strongly dependent on (1) lignin type, (2) cross-linking/oxyethylation degrees of OEL, (3) corresponding swelling properties, and (4) OEL concentrations in model soils.

)-H azidated materials under electrocatalytic conditions. The functionalized polymers were obtained with high retention of mass average molecular mass and high functionalization through chemo-selective mangana-electrocatalysis. Our strategy proved to be broadly applicable to a variety of homo- and copolymers. Polyethylene, polypropylene as well as post-consumer polystyrene materials were functionalized by this approach, thereby avoiding the use of hypervalent-iodine reagents in stoichiometric quantities by means of electrocatalysis. This study, hence, represents a chemical oxidant-free polymer functionalization by electro-oxidation. The electrocatalysis proved to be scalable, which highlights its unique feature for a green hydrogen economy by means of the hydrogen evolution reaction (HER).

Abstract The article contains sections titled: 1. Occurrence and Functions 2. Structure and Biosynthesis 3. Physical Properties 4. Chemical Properties 4.1. Kraft Pulping 4.2. Sulfite Pulping 4.3. Other Pulping Processes 4.4. Pulp Bleaching 4.5. Yellowing Reactions 5. Commercial Lignins 6. Analysis 6.1. Detection and Quantification 6.2. Isolation 6.3. Spectroscopic Methods 6.4. Degradation Methods 6.5. Molar Mass Determination 7. Uses 8. Toxicology

The vascular cambium is the meristem in trees that produce wood. This meristem consists of two types of neighbouring initials: fusiform cambial cells (FCCs), which give rise to the axial cell system (i.e. fibres and vessel elements), and ray cambial cells (RCCs), which give rise to rays. There is little molecular information on the mechanisms whereby the differing characteristics of these neighbouring cells are maintained. A microgenomic approach was adopted in which the transcriptomes of FCCs and RCCs dissected out from the cambial meristem of poplar (Populus trichocarpa x Populus deltoïdes var. Boelare) were analysed, and a transcriptional database for these two cell types established. Photosynthesis genes were overrepresented in RCCs, providing molecular support for the presence of photosynthetic systems in rays. Genes that putatively encode transporters (vesicle, lipid and metal ion transporters and aquaporins) in RCCs were also identified. In addition, many cell wall-related genes showed cell type-specific expression patterns. Notably, genes involved in pectin metabolism and xyloglucan metabolism were overrepresented in RCCs and FCCs, respectively. The results demonstrate the use of microgenomics to reveal differences in biological processes in neighbouring meristematic cells, and to identify key genes involved in these processes.

Abstract Because of the growing utilization of renewable raw materials, the technical use of lignocellulosic fibres from wood and other annual plant materials is becoming increasingly important. The conventional production process of fibreboards is characterized by high‐energy consumption and use of ecologically insecure synthetic lesins. Approximately 40 to 45% of the total energy expenditure are used for the thermo‐mechanical pulping. Because of high plastication temperatures, an inactive lignin crust on the fibre surface is formed. For that reason, for glueing of the fibres, urea formaldehyde and melamin resins are usually used. The costs for the resin amount to approximately 50% of the entire material costs. In addition, environmental problems are caused. The aim of our investigation is the reduction of energy and resin consumption by enzymatic modification of wood chips and the enzymatic activation of the inherent bonding strength of the material. The first industrial use of fungi for the modification of wood was in the production of “Myco wood”. Pleurothus ostreatus and Trametes versicolor were applied for nonsterile delignification of beech wood. The present investigation of the authors deals with the mycological pre‐treatment of wood chips in order to reduce the energy consumption during wood pulping. The screening results favour the brown rotter Gleophyllum trabeum for pinewood (Pinus silvestris) and the white rotter Trametes hirsuta for beech (Fagus silvatica) . Both species show resistance against mould fungi. The use of submerged inoculum of these fungi has the advantage over wheat inoculum that the lag phase is less than 12 hours and that the addition of nutrients or fungicides is not necessary. Short‐time wood chip incubation results in a 40% decrease of energy consumption during thermo‐mechanical pulping and in improved fibreboard properties. Lignin reduction could not be determined by gravimetrical and x ‐ray microanalysis. Comparative investigations of fibre incubation using laccase, a submerged culture of Trametes versicolor and rape straw fibres show a high increase in bending and tensile strength and an improvement in the hygroscopic properties of glue‐free fibre boards for the last two incubation kinds. Similar effects have been obtained incubating pine wood fibres for the production of fibre sheets with enzyme medium of Trichoderma reseei .