Published by De Gruyter

Volume 71 Issue 7-8 - Special Issue: This issue contains selected papers from the 14th European Workshop on Lignocellulosics and Pulp (EWLP), June 28–30, 2016, Autrans, France / Guest Editors: Christine Chirat, Dominique Lachenal

Issue of Holzforschung

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Contents
Journal Overview

Publicly Available July 1, 2017

Editorial

June 27, 2017

Original Articles

March 31, 2017

About structural changes of lignin during kraft cooking and the kinetics of delignification

Cecilia Mattsson, Merima Hasani, Binh Dang, Maxim Mayzel, Hans Theliander

Page range: 545-553

Abstract

Wood meal was submitted to kraft cooking in a small-scale flow-through reactor and the structural changes of lignin have been investigated. The rate determining steps in kraft cooking were in focus. Based on two-dimensional nuclear magnetic resonance (2D-NMR) measurements on lignin fractions extracted at different cooking times from the black liquor, it was observed that the main lignin reactions occur within 10–20 min and thus the kinetics of the chemical reaction cannot be the rate-determining step. On the other hand, the molecular weight (MW) of lignin is shifted towards larger fragments in the course of cooking time but the MW decreases with increasing ionic strength. Obviously, the kinetics of the delignification are strongly dependent on solubility and/or mass transport at the cell wall level. At chip size level, the mass transport of cooking chemicals into the wood chip may influence the overall kinetics in the initial part of the cooking. At longer cooking times the concentration of chemicals becomes sufficiently high in the wood chips, and the delignification is progressively governed by solubility and/or mass transport of lignin molecules occurring at the cell wall level.

April 4, 2017

Utilization of lignin powder for manufacturing self-binding HDF

Ramunas Tupciauskas, Janis Gravitis, Janis Abolins, Andris Veveris, Martins Andzs, Tiina Liitia, Tarja Tamminen

Page range: 555-561

Abstract

The preparation of self-binding lignocellulosic fibreboards has been investigated. Different high-density fibreboards (HDF) were hot-pressed based on a mixture of grey alder ( Alnus incana L. Moench) wood chips processed by steam explosion auto-hydrolysis (SE) and 15% or 25% lignin content from three different industrial sources: softwood kraft lignin (SWKL), soda wheat straw lignin (SoWhStL) and hydrolysis wheat straw lignin (HWhStL). Density, thickness swelling (TS) after immersion in water for 24 h, modulus of rupture (MOR), modulus of elasticity (MOE) and strength of internal bond (IB) of the board samples were determined. The amount (15% or 25%) and moisture content (MC) (18±1% or 5±2%) of the added lignin affected all the tested properties of the HDF except for density. However, the kind of the added lignin affects the obtained fibreboard more significantly compared to the control sample made without an admixture of lignin. In some cases, the tested values were diminished to half. The tested properties of the HDF samples produced with SoWhStL or HWhStL are compatible with standard requirements for medium-density fibreboard (MDF) for general use under dry conditions (EN 622-5, MDF), however, it depends on the lignin amount and MC.

April 7, 2017

Consecutive determination of softwood kraft lignin structure and molar mass from NMR measurements

Jerk Rönnols, Anna Jacobs, Fredrik Aldaeus

Page range: 563-570

Abstract

The general molecular properties and in particular, the molar mass of lignin are of central importance for industrial applications, as these data govern important thermal and mechanical characteristics. The focus of the present paper is pulsed field gradient-nuclear magnetic resonance (PFG-NMR), which is suitable for determination of lignins’ weight-average molar mass, based on diffusion constants. The method is calibrated by lignin fractions characterized by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). It could be demonstrated on a set of softwood kraft lignins that the PFG-NMR approach gives results in very good agreement with those obtained using conventional size exclusion chromatography (SEC).

May 25, 2017

Production of hemicellulose oligomers from softwood chips using autohydrolysis followed by an enzymatic post-hydrolysis

Vivien Deloule, Christine Chirat, Claire Boisset, Bertrand Toussaint, Jadwiga Chroboczek

Page range: 575-581

Abstract

In the context of value added valorization of hemicelluloses (HCs), their soft extraction by autohydrolysis (AH) of softwood (SW) chips has been optimized via the temperature/time parameters (170°C/2 h, 170°C/1 h and 150°C/1 h). Two enzyme mixtures containing mainly a glucanase and a mannanase were used to decrease the degree of polymerization (DP) of the extracted HCs. Hydrolysates containing HCs were analyzed in terms of monomers and oligomers, molecular weight distribution (MWD) and chemical composition. The MW was strongly dependent on AH conditions: most of the water-soluble HCs with 1800 Da MW were obtained at 150°C/1 h. The parameters 170°C/2 h gave rise to MWs<1800 Da. Enzymatic hydrolysis (EH) reduced efficiently the DP of HCs, and the glucosidase was more efficient than the mannanase, but the former also hydrolyzed more oligomers into their monomeric components.

March 22, 2017

Morphological features of aerogels and carbogels based on lignosulfonates

Olga Brovko, Irina Palamarchuk, Konstantin Bogolitsyn, Dmitriy Chukhchin, Artem Ivakhnov, Natalia Valchuk

Page range: 583-590

Abstract

The synthesis of new carbogels based on sodium lignosulfonates alone (LSNa) and interpolyelectrolyte complexes (IPEC) made by a combination of lignosulfonate and chitosan (CT) (i.e. IPEC-LSNa-CT) was investigated. The IPECs were converted into carbogels by slow and rapid pyrolysis (Py slow and Py rapid ) and the influence of Py conditions on the formation of carbogels was established. It is demonstrated that the obtained carbogels have a high microporous structure with elevated total porosity values. The porosity of synthesised carbogels is on the nanoscale level, while about 80% of the internal surfaces obtained by both Py slow and Py fast is in the range of 0.7–1.0 nm pore size. It was found that elements of the initial precursor structure (LSNa) are stored in the carbon aerogels, if obtained by the appropriate pyrolysis technique.

March 22, 2017

Wood based activated carbons for supercapacitor electrodes with sulfuric acid electrolyte

Galina Dobele, Aleksandrs Volperts, Aivars Zhurinsh, Darya Vervikishko, Evgeny Shkolnikov, Jurijs Ozolinsh

Page range: 591-598

Abstract

Activated carbons (ACs) based on wood charcoal were synthesized via sodium hydroxide activation and studied as electrode material in supercapacitors (sulfuric acid electrolyte). In focus were the porous structure of the ACs and their electrochemical properties as a function of the synthesis conditions. The data of surface area and pore volume and pore size dimensions (determined by N 2 adsorption and evaluated based on three theories) of the ACs activated at 700°C and with NaOH/carbonizate ratios of 2 and 3.7 are reported, such as the specific capacitance (F g −1 ), specific resistance (Ohm cm), electrolyte volume (mm 3 g −1 ) and the specific power capacity of a cell (Wh kg −1 ) of the supercapacitors made of various ACs. It was established that the porosity is increasing with increasing activation temperature and activator rate while the specific capacitance of the device increased up to 390 F g −1 based on elementary cell mass.

April 22, 2017

New insights into the decomposition mechanism of chlorine dioxide at alkaline pH

Jennifer Marcon, Gérard Mortha, Nathalie Marlin, Florian Molton, Carole Duboc, Auphélia Burnet

Page range: 599-610

Abstract

The mechanism of chlorine dioxide (ClO 2 ) decomposition in an alkaline medium has been investigated. The formation of radicals and chlorinated species was studied in aqueous solutions containing ClO 2 and simple model compounds of lignin or cellulose (vanillin, vanillyl alcohol, veratryl alcohol, methylglucoside and cellobiose) at acidic and alkaline pHs. Because hypochlorite (ClO − ) is an intermediate occurring in the course of the reaction mechanism, similar experiments were carried out with solutions of sodium hypochlorite (NaClO) at alkaline and acidic pHs. Electron paramagnetic resonance (EPR) spectroscopy based on the spin-trapping technique revealed the presence of hydroxyl radicals (HO˙) at alkaline pH with ClO 2 alone or with model compounds. At the same pH, only a small amount of HO˙ was detected with ClO − . Chlorite (ClO 2 − ) and chlorate (ClO 3 − ) ions were dosed with iodometric titrations, both during ClO 2 alkaline decomposition and during reactions with model compounds. Vanillin and vanillyl alcohol were oxidized by ClO 2 . The intermediate ClO 2 − was either inert or reacted with the aldehyde function of vanillin. Cellobiose was attacked only in an alkaline medium, either directly by ClO 2 or indirectly by HO˙ radicals. This resulted in the formation of glucose, which was then degraded by ClO 2 − ions. The generation of HO˙ could be one reason for cellulose degradation by ClO 2 at alkaline pH, but possibly not the unique one, as it was not proved in this article, whether or not ClO 2 is able to directly attach the OH functions of anhydrosugars at alkaline pH.

April 22, 2017

Upgrading of commercial pulps to high-purity dissolving pulps by an ionic liquid-based extraction method

Petra Wollboldt, Michael Strach, Axel Russler, Stepanka Jankova, Herbert Sixta

Page range: 611-618

Abstract

In the course of the Ioncell-P process, hemicelluloses are extracted from wood pulps by a mild treatment with an ionic liquid (IL) water mixture, and the result is a high-purity dissolving pulp. The aim of the present work is to study the influence of pulp origin concerning different wood species and pulping processes on the resulting pulp purity and yield after extraction with IL/water, while the IL is 1-ethyl-3-methylimidazolium acetate ([emim][OAc]). The raw materials were chosen from commercial alkaline kraft and acid sulfite paper and dissolving pulps prepared from both hardwood (HW) and softwood (SW). The extraction was followed by a filtration step to separate the cellulose and the hemicellulose fractions. The hemicelluloses were precipitated from the IL/water filtrate. In general, the Ioncell-P process proved to be more selective toward the removal of xylan as compared to glucomannan indicating that HW pulps are easier to purify than those of SW. It was possible to reach high alpha pulp qualities by the extraction process.

May 3, 2017

Hardwood kraft pulp structural features affecting refinability

Cátia T. Sousa, Dmitry V. Evtuguin, José L. Amaral

Page range: 619-624

Abstract

Two industrial bleached Eucalyptus globulus kraft pulps (pulps A and B), cooked from the same wood stock with slightly different alkali charges and temperatures, showed different refinability in the laboratory beating of pulp using a PFI mill. The easy to refine pulp (A) and the difficult to refine pulp (B) did not reveal significant differences in their biometric data and general chemical composition, but pulp A showed ca. 5%–10% higher mechanical strength and twice as high refinability compared to pulp B. These differences were ascribed to slightly higher intrinsic viscosity and higher xylan content of pulp A compared to pulp B (1010 vs. 860 cm 3 g −1 and 20.1 vs. 17.8%, respectively). The xylan structure and its location in fiber cells were also different, which affected the pulp’s refinability. The presence of high proportion of xylan in the bulk of fibers, rather than in their outer layers, seems to favor the pulp beating. An interpretation was also proposed, according to which the aggregation of cellulose fibrils during cooking, i.e. a partial coalescence of fibril crystallites, may also have a negative effect on pulp refinability.

April 26, 2017

Brightness stability of eucalyptus-dissolving pulps: effect of the bleaching sequence

Jordan Perrin, Dominique Lachenal, Christine Chirat

Page range: 625-631

Abstract

The factors governing the brightness reversion (BR) of dissolving pulps under heat exposure are investigated. Carbonyl (CO) groups were artificially introduced on fully bleached pulp by sodium hypochlorite (NaClO) oxidation. It was demonstrated that the CO groups are responsible for loss of brightness stability (BS). These groups were partly eliminated by an alkaline extraction stage (E), which improved BS. However, an alkaline peroxide stage (P) was more efficient than E to improve BS, but without any additional CO loss. Moreover, an unbleached dissolving pulp was bleached in the laboratory by elemental chlorine free (ECF) and totally chlorine free (TCF) [ozone-based] sequences to the same brightness. The very low CO content was about the same in both cases. The ECF-bleached pulp showed substantially lower BS than the TCF pulp. These results are interpreted such that the chemistry of chromophores in the unbleached pulp also governs BS. In situ detection of phenolic and quinone chromophores in bleached dissolving pulp was performed by electron paramagnetic resonance (EPR) spectroscopy and ultraviolet resonance Raman (UVRR) spectroscopy. The content of these groups was bleaching-sequence-dependent, which may be related to the BS differences.

April 12, 2017

Cellulose fiber based fungal and water resistant insulation materials

Chao Zheng, Dongfang Li, Anna Ottenhall, Monica Ek

Page range: 633-639

Abstract

The development of thermal insulation materials from sustainable, natural fibrous materials is desirable. In the present study, cellulose fiber based insulation foams made of bleached chemi thermo mechanical pulp (CTMP) have been investigated. To improve water resistance, the foams were impregnated with hydrophobic extractives from the outer bark of birch ( Betula verrucosa ) and dried. The surface morphology of the foams and the distribution of the deposited particles from the extractives were observed by scanning electron microscopy (SEM). The modified foams showed improved water resistance, as they did not disintegrate after immersion in water for 7 days, whereas the unmodified foam did. Compared to the unmodified foam, the modified foams absorbed 50% less moisture within 24 h. The modification had no negative effects on the thermal insulation properties, fungal resistance or compressive strength of the foams. The proposed approach is simple and can be easily integrated into plants working based on the biorefinery concept.

June 28, 2017

Biomass conversion into blow-in heat insulation materials by steam explosion

Martins Andzs, Ramunas Tupciauskas, Andris Veveris, Laura Andze, Janis Abolins, Janis Gravitis

Page range: 641-644

Abstract

The study of converting grey alder ( Alnus incana ) chips and silver birch ( Betula pendula ) flakes – residues from plywood manufacture – into blow-in insulation material by steam explosion (SE) is reported. The SE was conducted at temperatures between 200 and 235°C, for 0–5 min at pressures between 16 and 32 MPa. The severity parameters (log R 0 ) of the SE was calculated, from which log R 0 ≈3.6 was the most appropriate for production of blow-in materials. Thermal conductivity of the obtained insulating material was found to be in the range of 0.053–0.057 W m −1 ·K −1 .

May 12, 2017

Effect of cationic polyelectrolytes in contact-active antibacterial layer-by-layer functionalization

Chao Chen, Josefin Illergård, Lars Wågberg, Monica Ek

Page range: 649-658

Abstract

Contact-active surfaces have been created by means of the layer-by-layer (LbL) modification technique, which is based on previous observations that cellulose fibers treated with polyelectrolyte multilayers with polyvinylamine (PVAm) are perfectly protected against bacteria. Several different cationic polyelectrolytes were applied, including PVAm, two different poly(diallyl dimethyl ammonium chloride) polymers and two different poly(allylamine hydrochloride) polymers. The polyelectrolytes were self-organized in one or three layers on cellulosic fibers in combination with polyacrylic acid by the LbL method, and their antibacterial activities were evaluated. The modified cellulose fibers showed remarkable bacterial removal activities and inhibited bacterial growth. It was shown that the interaction between bacteria and modified fibers is not merely a charge interaction because a certain degree of bacterial cell deformation was observed on the modified fiber surfaces. Charge properties of the modified fibers were determined based on polyelectrolyte titration and zeta potential measurements, and a correlation between high charge density and antibacterial efficiency was observed for the PVAm and PDADMAC samples. It was demonstrated that it is possible to achieve antibacterial effects by the surface modification of cellulosic fibers via the LbL technique with different cationic polyelectrolytes.

May 16, 2017

Nanocelluloses obtained by ammonium persulfate (APS) oxidation of bleached kraft pulp (BKP) and bacterial cellulose (BC) and their application in biocomposite films together with chitosan

Linda Vecbiskena, Linda Rozenberga

Page range: 659-666

Abstract

Bleached birch kraft pulp (BKP, Södra Cell AB, Sweden) and unmodified bacterial cellulose (BC) pellicles, biosynthesized by the bacterium Komagataeibacter rhaeticus , were converted to cellulose nanofibers via ammonium persulfate (APS) oxidation. Fiber dimensions were investigated in an atomic force microscope, and the crystallite size was calculated by Rietveld analysis. Saos-2 osteosarcoma cell line served to assess the in vitro cytocompatibility of the biocomposite films. Results showed that individual cellulose nanofibers with an average width of 80±15 nm and a length between 600 and 1200 nm are formed by APS oxidation. The obtained BC nanofibers can be promising constituents in nanocellulose films and in chitosan-matrix films with improved physical-mechanical and biological properties. Good cellular biocompatibility was found for chitosan/oxidized cellulose films; the viability of Saos-2 osteosarcoma cells was higher on chitosan/oxidized BC films compared to chitosan/oxidized BKP films.

May 5, 2017

Volatile terpene extraction of spruce, fir and maritime pine wood: supercritical CO₂ extraction compared to classical solvent extractions and steam distillation

Frédérique Bertaud, Christelle Crampon, Elisabeth Badens

Page range: 667-673

Abstract

To evaluate the potential recovery rate of volatile terpenes from pulp mills, different extraction methods were performed on fir, spruce and maritime pine, and the extracts were analyzed by gas chromatography-flame ionization detector/mass spectroscopy (GC-FID/MS). The results obtained by traditional solvent extraction in the Soxhlet and the accelerated solvent extraction (ASE) ® apparatus were compared with those of steam distillation technology (Clevenger), and supercritical CO 2 (SC-CO 2 ) extraction was also tested as an interesting alternative to extraction with liquid organic solvents. ASE ® -Dionex applied on freeze-dried samples with successive extraction with n-hexane and acetone/water (95/5) was not suitable for volatile compounds. Steam distillation applied on fresh and ground samples was very specific of volatiles, but did not allow complete extraction. Soxhlet extraction performed on fresh and ground samples with successive application of acetone and acetone/cyclohexane (1/9) gave the most representative quantification of ground wood chips, together for volatile terpenes, resins and fatty-acid-type compounds. SC-CO 2 [20 and 30 MPa, 60°C modified by 5% ethanol (EtOH)] is able to extract most of the terpenes, terpenoids and fatty-acid-type compounds, but the extraction rates of volatiles were very limited because of a pre-drying step (freeze-drying and crushing). Other lipophilic extractives were also recovered to a lesser extent.

March 28, 2017

Protective effects of proanthocyanidins extracts from the bark of deciduous trees in lipid systems

Sarmite Janceva, Liga Lauberte, Tatiana Dizhbite, Jelena Krasilnikova, Galina Telysheva, Marcis Dzenis

Page range: 675-680

Abstract

Oligomeric proanthocyanidins (OPC) rich extracts (OPCEs) were isolated by sequential extraction from the bark of the deciduous trees grey alder ( Alnus incana ), black alder ( Alnus glutinosa ) and goat willow ( Salix caprea ). The yields of OPCE from all barks under study were rather similar and varied between 12.3% and 15.4% based on the oven dry (o.d.) bark. Content of proanthocyanidins in OPCEs ranged from 16.6% to 25% based on o.d. extract. The OPCEs were characterised by means of antioxidant activity with ABTS˙ + and DPPH˙ radical scavenging tests. All extracts being introduced into lipid-based substrates, i.e. mayonnaise and a basic composition of a cosmetic cream, showed antioxidant activity comparable to the reference commercial antioxidant tert -butylhydroquinone (TBHQ). The results of in vitro tests have revealed that the OPCEs could be useful for the human organism as they activated malfunctions of amylase, inhibited pancreatic lipase activity (duodenal digestion model), decreased lipid absorption in blood and decreased pyruvate level in blood plasma essential for regulation of carbohydrate metabolism. The data obtained confirms the advantages of OPC and OPCEs applications as an antioxidant additive for food, cosmetic and health industries.

Short Notes

June 24, 2017

Steam explosion treatments of technical hydrolysis lignin

Stepan Krutov, Elena Ipatova, Aleksander Vasilyev

Page range: 571-574

Abstract

Technical hydrolysis lignins, both freshly obtained and stored longterm under atmosphere conditions, were treated by steam explosion (SE, 235°C/3.2 MPa) for 1, 2, and 3 min. The SE treated lignins were characterized by means of solid-state 13 C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. It was found that SE leads to significant changes in morphological and chemical properties of lignin due to oxidation, condensation and hydrolytic destruction.

April 20, 2017

Moisture absorption properties of hardwood veneers modified by a sol-gel process

Edgars Kirilovs, Silvija Kukle, Janis Gravitis, Hans-Jörg Gusovius

Page range: 645-648

Abstract

A new invisible nanolevel coating has been developed based on the sol-gel process for veneer finishes. The sol synthesis and its application as a protective agent is described. It could be demonstrated that a combination of organic light stabilizers and sol-gel deposits is feasible and that the resulting hybrid inorganic-organic thin films decrease moisture uptake of hardwood veneers.

About this journal

Objective
Holzforschung (HF) is an international scholarly journal that publishes cutting-edge research on the biology, chemistry, physics and technology of wood and wood components. High quality papers about biotechnology and tree genetics are also welcome. Rated year after year as one of the top scientific journals in the category of Pulp and Paper (ISI Journal Citation Index), Holzforschung represents innovative, high quality basic and applied research. The German title reflects the journal's origins in a long scientific tradition, but all articles are published in English to stimulate and promote cooperation between experts all over the world. Ahead-of-print publishing ensures fastest possible knowledge transfer.

Topics

Biology, chemistry, physics and technology of wood and wood components
Biotechnology and tree genetics

Article formats
Original articles, Reviews, Short notes

> Information on submission process

Volume 71 Issue 7-8 - Special Issue: This issue contains selected papers from the 14th European Workshop on Lignocellulosics and Pulp (EWLP), June 28–30, 2016, Autrans, France / Guest Editors: Christine Chirat, Dominique Lachenal

Issue of Holzforschung

Frontmatter

Editorial

About structural changes of lignin during kraft cooking and the kinetics of delignification

Abstract

Utilization of lignin powder for manufacturing self-binding HDF

Abstract

Consecutive determination of softwood kraft lignin structure and molar mass from NMR measurements

Abstract

Production of hemicellulose oligomers from softwood chips using autohydrolysis followed by an enzymatic post-hydrolysis

Abstract

Morphological features of aerogels and carbogels based on lignosulfonates

Abstract

Wood based activated carbons for supercapacitor electrodes with sulfuric acid electrolyte

Abstract

New insights into the decomposition mechanism of chlorine dioxide at alkaline pH

Abstract

Upgrading of commercial pulps to high-purity dissolving pulps by an ionic liquid-based extraction method

Abstract

Hardwood kraft pulp structural features affecting refinability

Abstract

Brightness stability of eucalyptus-dissolving pulps: effect of the bleaching sequence

Abstract

Cellulose fiber based fungal and water resistant insulation materials

Abstract

Biomass conversion into blow-in heat insulation materials by steam explosion

Abstract

Effect of cationic polyelectrolytes in contact-active antibacterial layer-by-layer functionalization

Abstract

Nanocelluloses obtained by ammonium persulfate (APS) oxidation of bleached kraft pulp (BKP) and bacterial cellulose (BC) and their application in biocomposite films together with chitosan

Abstract

Volatile terpene extraction of spruce, fir and maritime pine wood: supercritical CO2 extraction compared to classical solvent extractions and steam distillation

Abstract

Protective effects of proanthocyanidins extracts from the bark of deciduous trees in lipid systems

Abstract

Steam explosion treatments of technical hydrolysis lignin

Abstract

Moisture absorption properties of hardwood veneers modified by a sol-gel process

Abstract

Volatile terpene extraction of spruce, fir and maritime pine wood: supercritical CO₂ extraction compared to classical solvent extractions and steam distillation