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  • 1.
    Abächerli, A
    et al.
    International lignin institute, Switzerland.
    Gosselink, R
    Agrotechnology & Food Innovations, The Netherlands.
    Jong, E. de
    Agrotechnology & Food Innovations, The Netherlands.
    Baumberger, S
    French National Institute for Agricultural Research.
    Hortling, B
    KCL.
    Bonini, C
    USB.
    D'Auria, M
    USB.
    Zimbardi, F
    ENEA.
    Barisano, D
    ENEA.
    Duarte, J
    INETI.
    Sena-Martins, G
    INETI.
    Ribeiro, B
    INETI.
    Koukios, E
    NTUA.
    Koullas, D
    NTUA.
    Avgerinos, E
    NTUA.
    Vasile, C
    PPI.
    Cazacu, G
    PPI.
    Mathey, R
    Granit.
    Ghidoni, D
    Granit.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE).
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Quintus-Leino, P
    VTT.
    Piepponen, S
    VTT.
    Laine, A
    VTT.
    Koskinen, P
    VTT.
    Gravitis, J
    LSIWC.
    Suren, J
    Bakelite.
    Fasching, M
    Lenzing.
    Intermediary status of the round Robins in the eurolignin network2005Konferensbidrag (Refereegranskat)
  • 2. Ala-Kaila, K.
    et al.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Chemical character of the response of softwood kraft pulp towards industrial two-stage oxygen-alkali delignification2004Ingår i: Paperi ja puu, ISSN 0031-1243, Vol. 86, nr 5, s. 353-358Artikel, forskningsöversikt (Refereegranskat)
    Abstract [fi]

    The transient behavior of residual material affecting the kappa number of softwood kraft pulp (termed residual lignin), was tested experimentally step-wise in an industrial two-stage oxygen-alkali delignification process. The behavior was characterized by leaching the pulps and dividing the residual lignin into four different fractions to represent the wash loss fraction, the easily leachable fraction, the slowly leachable fraction and the stagnant fraction of the lignin in pulp. Further characterization was made regarding the chemical character of these fractions, i.e. residual lignin, extractives, hexenuronic acid, and other chemical structures that contribute to the kappa number of the pulps. The componential delignification response in the two oxygen-alkali reactors and the effects of the leaching operation were comprehensively assessed regarding the behavior of these different pulp components. The results were compared with results obtained earlier for birch kraft pulp originating from the same industrial process and treated using identical experimental procedures. Application: This study gives a new perspective with which to evaluate apparent and actual responses in industrial oxygen-alkali delignification of kraft pulps.

  • 3. Ala-Kaila, K.
    et al.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Sevastyanova, O.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Apparent and actual delignification response in industrial oxygen-alkali delignification of birch kraft pulp2003Ingår i: TAPPI Journal, ISSN 0734-1415, Vol. 2, nr 10, s. 23-27Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The time-dependent behavior of material that affects the kappa number of birch kraft pulp was experimentally tested in an industrial, two-stage, oxygen-alkali delignification process. The pulps were leached, and the leached material was divided into four different fractions: the wash loss fraction and the easily leachable, slowly leachable, and stagnant fractions. These fractions were further characterized according to their chemical natures, representing residual lignin, extractives, hexenuronic acids, and other chemical structures contributing to the kappa number of the pulps. The apparent and actual delignification responses in the two reactors and the effects of the leaching operation were thoroughly evaluated based on the behaviors to these different pulp components.

  • 4.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Investigation of the Molecular Weight Increase of Commercial Lignosulfonates by Laccase Catalysis2010Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, nr 4, s. 904-910Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed.

  • 5.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Polymerization of lignosulohonates by laccase - from model studies to application evaluation trials2010Ingår i: Oxidative enzymes as sustainable industrial biocatalysts / [ed] G Feijoo and MT Moreira, 2010, s. 151-156Konferensbidrag (Refereegranskat)
  • 6.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Reaction mechanism of laccase-catalyzed polymerization of lignin revealed with model study2008Ingår i: 10th European workshop on lignocellulosics and pulp proceedings, 2008, s. 101-104Konferensbidrag (Refereegranskat)
  • 7.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Structural modification of commercial lignosulphonates through laccase catalysis and ozonolysis2010Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 32, nr 3, s. 458-466Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignosulphonates are by-products from the sulphite pulping process, in which lignin is separated from cellulose by the addition of sulphonic acid groups to the alpha-position of lignin, thereby increasing the solubility of lignin in water. The predominant industrial utilisations of lignosulphonates are as dispersants, plasticisers and water-reducing agents in concrete preparation. The ability of lignosulphonates to function as a good plasticisers and water reducers is intimately linked with the purity of the lignosulphonate, its molecular weight and the number of charged groups present in the macromolecule. Currently, lignosulphonates are outrivaled by synthetic plasticisers termed superplasticisers due to their superior properties when used as additives to high-strength concrete. If lignosulphonates are to successfully compete with these superplasticisers, significant modifications are required. This paper describes a two-stage treatment of lignosulphonates in which the molecular weight is increased through laccase oxidation and carboxylic groups are introduced through ozonolysis. The technical significance of the results is also discussed.

  • 8.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Nousiainen, Paula
    University of Helsinki, Department of Chemistry.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Sipilä, Jussi
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Oxidative polymerisation of models for phenolic lignin end-groups by laccase2010Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, nr 1, s. 21-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The redox enzyme laccase can lead to cross-linking of lignin molecules by oxidising phenolic end groups to resonance-stabilised radicals that can undergo radical coupling to form covalent bonds. This property has potential for many technical applications. However, laccase treatment can also lead to degradation. Experiments were performed with two laccases of different oxidation potential and pH and temperature optima. The predominant reaction following laccase oxidation is the formation of 5-5' and 4-O-5' bonds. If the 5-position is blocked, other reactions occur, including coupling of the 1-position and oxidation of the a-position, which aggravates cross-linking of different lignin molecules. The product profile generated by the two laccases is somewhat different, mainly because of the different pH rather than differences in enzyme activity. Reaction mechanisms and the technical and biological significance of the results are discussed.

  • 9.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Nousiainen, Paula
    University of Helsinki, Department of Chemistry.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Sipilä, Jussi
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Sulfonation of phenolic end groups in lignin directs laccase-initiated reactions towards cross-linking2010Ingår i: Industrial Biotechnology, ISSN 1550-9087, E-ISSN 1931-8421, Vol. 6, nr 1, s. 50-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of sulfonation of the a-carbon on model compounds representing phenolic end groups on lignin was studied with respect to the reactions initiated by oxidation of laccase, by mass spectrometry. Sulfonation seems to direct the reactions towards formation of 5-5´ and 4-O-5´ bonds, avoiding formation of 1-O-4´ bonds and oxidation of the a-carbon. This, in turn, will facilitate cross-linking reactions between lignin molecules. Sulfonation therefore has potential as an industrial pretreatment prior to laccase treatment for various wood-containing materials.

  • 10. Baumberger, Stephanie
    et al.
    Abaecherli, Alfred
    Fasching, Mario
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gosselink, Richard
    Hortling, Bo
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Saake, Bodo
    de Jong, Ed
    Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method2007Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 61, nr 4, s. 459-468Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reactivity and physicochemical properties of lignins are partly governed by their molar mass distribution. The development of reliable standard methods for determination of the molar mass distribution is not only relevant for designing technical lignins for specific applications, but also for monitoring and elucidating delignification and pulping processes. Size-exclusion chromatography (SEC) offers many advantages, such as wide availability, short analysis time, low sample demand, and determination of molar mass distribution over a wide range. A collaborative study has been undertaken within the Eurolignin European thematic network to standardise SEC analysis of technical lignins. The high-molar-mass fraction of polydisperse lignins was shown to be the main source of intra- and interlaboratory variations, depending on the gel type, elution solvent, detection mode, and calculation strategy. The reliability of two widespread systems have been tested: one based on alkali and a hydrophilic gel (e.g., TSK Toyopearl gel) and the other based on THF as solvent and polystyrene-based gels (e.g., Styragel). A set of practical recommendations has been deduced.

  • 11.
    Bhardwaj, Jyoti
    et al.
    Univ Bristol, Adv Composites Ctr Innovat Sci & Technol, Bristol, Avon, England..
    Richardson, Robert
    Univ Bristol, Sch Phys, Bristol, Avon, England..
    Li, Jiebing
    KTH.
    Rahatekar, Sameer
    Univ Bristol, Bristol, Avon, England..
    Manufacturing strong regenerated cellulose fibers reinforced with cellulose nanocrystals2017Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Artikel i tidskrift (Övrigt vetenskapligt)
  • 12.
    Bohn Lima, Raquel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Brouwe, Jack
    Modeling and studies in direct carbon-biomass fuel cell for power generation2013Ingår i: Abstracts of Papers, 245th ACS National Meeting & Exposition, New Orleans, LA, United States, April 7-11, 2013, 2013, s. ENFL-526-Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Several factors such as the global energy supply security and the need for generating efficient and clean energy have increased the interest in the research related to alternative fuel and energy systems.  Among these alternative systems, the biomass-​fuelled integrated Direct Carbon Fuel Cell (DCFC) with solid oxide fuel cell (SOFC)​/molten carbonate fuel cell (MCFC) systems have been identified as one of key energy technologies for the future since it combines the merits of renewable energy sources and carbon​/hydrogen energy systems.The modeling of energy systems plays a crucial role in the estn. of the performance and selection of the configuration and the operation parameters of these systems.  In the case of integrated DCFC - SOFC​/MCFC systems, there are many aspects that should be considered for a complete and robust model.  The lack of such a model for integrated DCFC - SOFC​/MCFC and biomass systems in the literature have been the main motivation for this study.

  • 13.
    Bohn Lima, Raquel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Khan, Mohammed A.
    Core-shell ceria-carbonates nanocomposite electrolyte for Lignin based fuel cell2014Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, s. 66-ENFL-Artikel i tidskrift (Övrigt vetenskapligt)
  • 14.
    Bohn Lima, Raquel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Raza, Rizwan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Ceria-carbonates nanocomposite electrolyte for lignin based fuel cell2012Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikel i tidskrift (Övrigt vetenskapligt)
  • 15. Cadena, Edith M.
    et al.
    Du, Xueyu
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Fillat, Amanda
    García-Ubasart, Jordi
    Vidal, Teresa
    Colom, Josep F.
    On hexenuronic acid (HexA) removal and mediator coupling to pulp fiber in the laccase/mediator treatment2011Ingår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, nr 4, s. 3911-3917Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flax soda/AQ pulps were treated with different fungal laccase-mediator combinations followed by physical and chemical characterization of the pulps to obtain a thorough understanding of the laccase/mediator effects on hexenuronic acid (HexA) removal and the coupling of mediator onto pulps for fiber functionalization. Large differences were found and the presence of lauryl gallate (LG) during Trametes villosa laccase (TvL) treatment (TvL + LG) resulted in a much larger reduction of pulp-linked HexA than the combination of p-coumaric acid (PCA) and Pycnoporus cinnabarinus laccase (PcL). A major portion of LG became attached to the pulp as revealed by an increase in the kappa number and further confirmed by thioacidolysis and H-1 NMR analysis of solubilized pulp fractions. Additional experiments with other chemical pulps and isolated pulp xylan and lignin revealed that HexA seems to be the sole pulp component attacked by TvL + LG. As a substrate for TvL, the reaction preference order is PCA > HexA > LG.

  • 16. del Rio, Jose C.
    et al.
    Rencoret, Jorge
    Marques, Gisela
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Jimenez-Barbero, Jesus
    Martinez, Angel T.
    Gutierrez, Ana
    Structural Characterization of the Lignin from Jute (Corchorus capsularis) Fibers2009Ingår i: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 57, nr 21, s. 10271-10281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structural characteristics of the lignin from jute (Corchorus capsularis) fibers, which are used for high-quality paper pulp production, were studied. The lignin content (13.3% Klason lignin) was high compared to other nonwoody bast fibers used for pulp production. The lignin structure was characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 2D-NMR, and thioacidolysis. Upon Py-GC/MS, jute fibers released predominantly products from syringylpropanoid units with the S/G ratio being 2.1 and a H/G/S composition of 2:33:65. 2D-NMR of the milled wood lignin (MWL) isolated from jute fibers showed a predominance of beta-O-4' aryl ether linkages (72% of total side chains), followed by beta-beta' resinol-type linkages (16% of total side chains) and lower amounts of beta-5' phenylcoumaran (4%) and beta-1' spirodienone-type (4%) linkages and cinnamyl end groups (4%). The high predominance of the S-lignin units, together with the high proportion of beta-O-4' aryl ether linkages, which are easily cleaved during alkaline cooking, are advantageous for pulping. On the other hand, a small percentage (ca. 4%) of the lignin side chain was found to be acetylated at the gamma-carbon, predominantly over syringyl units. The analysis of desulphurated thioacidolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds and the type of units (syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, the major part of the beta-beta' dimers included two syringyl units, indicating that most of the beta-beta' substructures identified in the HSQC spectra were of the syringaresinol type (pinoresinol being absent), as already observed in the lignin of other angiosperms.

  • 17.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Eugenio Martin, Maria E.
    Instituto Nacional de Investigacion y Tecnologias Agrarias y Alimentarias.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Improvement of kraft pulp bleaching by treatments with laccase, urea, and refining2013Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, nr 6, s. 651-658Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Unbleached Eucalyptus kraft pulps were treated by three methods and the bleaching effects have been evaluated. The treatments were performed by a laccase mediator system (LMS), refining (R), and urea (U) alone and in combination of these methods. The bleached pulps were characterized in terms of κ number, hexenuronic acid content, brightness, and viscosity. In addition, the lignin-carbohydrate complexes (LCCs) were fractionated and characterized with regard to the fractionation yield, lignin content, and carbohydrate composition. Moreover, the 1 H nuclear magnetic resonance spectra were recorded and the thioacidolysis-gas chromatography and thioacidolysis-size exclusion chromatography analyses were performed. The LMS treatment resulted mainly in a slightly better delignification as manifested by a κ number (K no.) reduction of 0.8 units. The effects of the U treatment included delignification (1.4 κ units), hexenuronic acid removal (3 μ mol g-1), and improved pulp brightness (3.4 ISO units). The R treatment darkened the pulp (3 ISO units), whereas the bleaching of the R-pulp by subsequent LMS or U treatment enhanced the brightness (0.5 unit more) or delignification (0.3 unit more). The residual lignin in the pulp samples was present mainly as xylan-lignin. The Klason lignin content from the xylan lignin fraction decreased as the degree of delignification increased. The pulp darkening followed by the R treatment was interpreted as the result of the formation of condensed lignin structures, but these condensed lignins were substantially removed by the subsequent LMS or U treatment.

  • 18.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Universal fractionation of lignin-carbohydrate complexes (LCCs) from lignocellulosic biomass: an example using spruce wood2013Ingår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 74, nr 2, s. 328-338Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is of both theoretical and practical importance to develop a universally applicable approach for the fractionation and sensitive lignin characterization of lignin-carbohydrate complexes (LCCs) from all types of lignocellulosic biomass, both natively and after various types of processing. In the present study, a previously reported fractionation approach that is applicable for eucalyptus (hardwood) and flax (non-wood) was further improved by introducing an additional step of barium hydroxide precipitation to isolate the mannan-enriched LCC (glucomannan-lignin, GML), in order to suit softwood species as well. Spruce wood was used as the softwood sample. As indicated by the recovery yield and composition analysis, all of the lignin was recovered in three LCC fractions: a glucan-enriched fraction (glucan-lignin, GL), a mannan-enriched fraction (GML) and a xylan-enriched fraction (xylan-lignin, XL). All of the LCCs had high molecular masses and were insoluble or barely soluble in a dioxane/water solution. Carbohydrate and lignin signals were observed in H-1 NMR, C-13 CP-MAS NMR and normal- or high-sensitivity 2D HSQC NMR analyses. The carbohydrate and lignin constituents in each LCC fraction are therefore believed to be chemically bonded rather than physically mixed with one another. The three LCC fractions were found to be distinctly different from each other in terms of their lignin structures, as revealed by highly sensitive analyses by thioacidolysis-GC, thioacidolysis-SEC and pyrolysis-GC.

  • 19.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    STRUCTURAL VERIFICATION OF LIGNIN-CARBOHYDRATE COMPLEX (LCC) STRUCTURES FROM SOFTWOOD FIBRES2010Ingår i: RESEARCH PROGRESS IN PAPER INDUSTRY AND BIOREFINERY (4TH ISETPP), VOLS 1-3 / [ed] Sun RC; Fu SY, GUANGZHOU: SOUTH CHINA UNIV TECHNOLOGY PRESS , 2010, s. 332-335Konferensbidrag (Refereegranskat)
    Abstract [en]

    The LCC fractionation process developed earlier by us for hardwood samples has been further improved to include an additional fractionation of glucomannan-lignin by a step of Ba(OH)(2) precipitation to suit softwood species better. Glucan-Lignin, Glucomannan-Lignin and Xylan-Lignin were thus obtained from spruce wood and subjected to SEC and NMR analysis and thioacidolysis followed by GC and SEC analysis respectively for structural elucidations. The LCC structures have been finally verified by comparisons with the LCC fractions prepared by another earlier developed softwood process.

  • 20.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Rencoret, Jorge
    Instituto de Recursos Naturales y Agrobiologia de Sevilla.
    Del Rio, Jose C.
    Instituto de Recursos Naturales y Agrobiologia de Sevilla.
    Martinez, Angel
    Centro de Investigaciones Biologicas.
    Gutierrez, Ana
    Instituto de Recursos Naturales y Agrobiologia de Sevilla.
    Understanding Pulp Delignification by Laccase-Mediator Systems through Isolation and Characterization of Lignin-Carbohydrate Complexes2013Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, nr 9, s. 3073-3080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects and mechanism of pulp delignificabon by laccases in the presence of redox mediators have been investigated on unbleached eucalyptus kraft pulp treated with laccases from Pycnoporus cinnabarinus (PcL) and Myceliophthora thermophila (MtL) and 1-hydroxybenzotriazole (HBT) and methyl syringate (MeS) as mediators, respectively. Determination of the corrected kappa number in eucalyptus pulps after the enzymatic treatments revealed that the PcL-HBT system exhibited a more remarkable delignification effect than the MtL-MeS system. To obtain further insight, lignin-carbohydrate complexes were fractionated and subsequently characterized by nuclear magnetic resonance, thioacidolysis (followed by gas chromatography and size exclusion chromatography), and pyrolysis-gas chromatography-mass spectrometry (pyrolysis-GC-MS) analyses before and after the enzymatic treatments and their controls. We can conclude that the laccase mediator treatments altered the lignin structures in such a way that more lignin was recovered in the xylan-lignin fractions, as shown by Klason lignin estimation, with smaller amounts of both syringyl (5) and guaiacyl (G) uncondensed units, as shown by thioacidolysis and gas chromatography, especially after the PcL-HBT treatment. The laccase mediator treatment produced oxidation at C alpha and cleavage of C alpha and C beta bonds in pulp lignin, as shown by pyrolysis-GC-MS. The general mechanism of residual lignin degradation in the pulp by laccase-mediator treatments is discussed in light of the results obtained.

  • 21.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Modification of industrial softwood kraft lignin using Mannich reaction with and without phenolation pretreatment2014Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 52, s. 729-735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The amination of industrial softwood kraft lignin was conducted using the Mannich reaction to modify the lignin structure for value-added applications. To understand the reaction mechanism and to quantify the amount of amine groups that were introduced, different types of NMR analyses were performed. The lignin was also pretreated by phenolation to increase its reactivity and the amount of the amine groups that were introduced. The Mannich reaction was very selective at the C-5 position of the guaiacyl units and complete under acidic conditions with similar to 11-fold amounts of reagents of dimethylamine and formaldehyde over either model lignin (4-hydroxy-3-methoxyacetophenone, HMAP) or industrial spruce kraft lignin (LignoBoost lignin, LBL). For LBL, 28 amine groups were introduced over 100 aromatic rings. By weight, the nitrogen content was 2.5%. The animated lignin was found to possess a higher molecular mass, reaching a Mp of 4.9 x 10(3) Da compared to the original 319 x 10(3) Da, and with a considerably increased dispersibility, especially in a dilute aqueous solution of hydrochloric acid (pH = 3), namely 5.2 mg/ml. With a preceding phenolation treatment, which increased the amount of phenolic aromatic rings available for the Mannich reaction, an introduction of 42 amine groups over 100 aromatic rings, or a nitrogen content of 4.8%, was obtained, which caused a further increase of the molecular mass to 5.1 x 10(3) Da (Mp) and of dispersibility in the aqueous solution of hydrochloric acid up to 32.0 mg/ml. The aminated lignins with or without the phenolation pretreatment formed very stable colloidal suspensions in water, with large particle sizes (391 and 39 nm), high zeta potentials (31.6 and 27.2 mV), and large charge densities (1.6 and 1.2 x 10(-7) equiv./ml, respectively). The potential value-added applications of these modified lignins with high amine contents include use as surfactant chemicals, polycationic materials and slow-release fertilisers, among others.

  • 22.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Modification of industrial kraft lignin by amination2012Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikel i tidskrift (Övrigt vetenskapligt)
  • 23.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Modification of lignin structure by amine group introduction2011Ingår i: Int. Symp. Wood, Fiber Pulping Chem. - Proc., ISWFPC, 2011, s. 298-303Konferensbidrag (Refereegranskat)
    Abstract [en]

    Amination of lignin conducted simply by Mannich reaction is an important mean for lignin structural and value upgradation. However, there is a lack of powerful analysis for quantification of the amine groups introduced and at the meantime for supplement of structural information about e.g. binding positions and side reactions etc. Various types of NMR analysis have thus been performed for the analysis of Mannich reaction products from lignin model, 4-hydroxy-3-methoxyacetophenone (HMAP), and from industrial spruce Kraft lignin. As revealed by NMRs, the reaction was very selective at C-5 position of guaiacyl lignin units and complete under acidic conditions with 11-fold amounts of reagents of piperidine (PIP) or dimethylamine (DMA) and formaldehyde over HMAP. No side reactions took place at the aromatic structure. For industrial lignin, 13.5 (by PIP) and 15 (by DMA) nitrogen atoms were introduced per 100 aromatic rings. Using other analytical methods, the aminated lignin was found with higher molecular weights, reaching Mp of 5.06kDa from the original 3.92kDa by DMA modification, and with a sharp increased solubility especially in acetic acid aqueous solution, 31.2 mg/ml after DMA modification. A preceding phenolation of the lignin resulted in a 70% increase of available aromatic rings and an introduction of 56 amine groups over 100 original aromatic rings after Mannich reaction by using DMA, which caused increases of molecular weights to 5.11kDa (Mp) and of solubility in acetic acid aqueous solution up to 77.2 mg/mL. Potential applications of these modified lignins of high values include many applications in different fields such as surfactant chemicals, polycationic materials and slow released fertilizers etc.

  • 24.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Perez Boada, Marta
    Centro de Investigaciones Biologicas.
    Rencoret, Jorge
    Instituto de Recursos Naturales y Agrobiologia de Sevilla.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Martinez, Angel
    Centro de Investigaciones Biologicas.
    Gutierrez, Ana
    Instituto de Recursos Naturales y Agrobiologia de Sevilla.
    Lignin-carbohydrate and lignin-lignin linkages in different lignin-carbohydrate complexes from spruce woodManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In order to characterize lignin-carbohydrate (LC) and lignin-lignin (LL) linkages in different lignin-carbohydrate complexes (LCCs), the glucan-lignin (GL), glucomannan-lignin (GML) and xylan-lignin (XL) isolated from spruce wood have been enzymatically hydrolyzed, using endoglucanase plus b-glucosidase (for GL and GML) or xylanase (for XL), followed by 2D HSQC NMR and Py-GC/MS analysis. It has been found that the enzymatic hydrolysis removed effectively most of the polysaccharide parts in the LCCs and thus enriched the lignin contents and LCC linkages so that various LC and LL linkages could be well demonstrated by the 2D HSQC NMR analysis. Three typical LC linkages, i.e. benzyl ether, γ-ester and phenyl glycoside, have been directly observed in the enzymatically hydrolyzed GML (En-GML) and enzymatically hydrolyzed XL (En-XL). There are two types of benzyl ether linkages, with primary and secondary OH from carbohydrates. There are three types of carbohydrate units linked with lignin by the phenyl glycoside bonds in the En-GML while only one type is found in the En-XL. It seems that mannose and galactose are among the sugar units involved in the linkages since their relative amounts in the sugar compositions increased after the enzymatic hydrolysis. From the LL linkages observed in the 2D HSQC NMR spectra, it was revealed that the lignin existing in GML is less condensed than the lignin from XL due to a higher percentage of β-O-4 sub-structure found in the former (75 % vs. 66 %). On the other hand, more other substructures have been found present in the lignin from XL than GML, e.g. phenylcoumaran (17 % vs. 15 %), dibenzodioxocin (9 % vs. 5 %), resinol (11 % vs. 6 %), and spirodienone (2 % vs. 1 %), implying more condensed lignin structures present in the XL. From the Py-GC/MS analysis, the relative amounts of guaiacol and coniferyl alcohol fragments over the acetoguaiacone fragment, an internal marker, were largely increased after the enzymatic hydrolysis, supporting the presences of even higher amounts of the phenyl glucoside LC linkages in the original LCCs since some of the linkages should have been cleaved during the enzymatic hydrolysis. The NMR analysis of the En-GL was not successful probably due to the attachment of the enzymes onto the GL structure or the existence of the remained crystalline cellulose structures.

  • 25.
    Du, Xueyu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Perez-Boada, Marta
    Fernandez, Carmen
    Rencoret, Jorge
    del Rio, Jose C.
    Jimenez-Barbero, Jesus
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gutierrez, Ana
    Martinez, Angel T.
    Analysis of lignin-carbohydrate and lignin-lignin linkages after hydrolase treatment of xylan-lignin, glucomannan-lignin and glucan-lignin complexes from spruce wood2014Ingår i: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 239, nr 5, s. 1079-1090Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Xylan-lignin (XL), glucomannan-lignin (GML) and glucan-lignin (GL) complexes were isolated from spruce wood, hydrolyzed with xylanase or endoglucanase/beta-glucosidase, and analyzed by analytical pyrolysis and 2D-NMR. The enzymatic hydrolysis removed most of the polysaccharide moieties in the complexes, and the lignin content and relative abundance of lignin-carbohydrate linkages increased. Analytical pyrolysis confirmed the action of the enzymatic hydrolysis, with strong decreases of levoglucosane and other carbohydrate-derived products. Unexpectedly it also revealed that the hydrolase treatment alters the pattern of lignin breakdown products, resulting in higher amounts of coniferyl alcohol. From the anomeric carbohydrate signals in the 2D-NMR spectra, phenyl glycoside linkages (undetectable in the original complexes) could be identified in the hydrolyzed GML complex. Lower amounts of glucuronosyl and benzyl ether linkages were also observed after the hydrolysis. From the 2D-NMR spectra of the hydrolyzed complexes, it was concluded that the lignin in GML is less condensed than in XL due to its higher content in beta-O-4' ether substructures (62 % of side chains in GML vs 53 % in XL) accompanied by more coniferyl alcohol end units (16 vs 13 %). In contrast, the XL lignin has more pinoresinols (11 vs 6 %) and dibenzodioxocins (9 vs 2 %) than the GML (and both have similar to 13 % phenylcoumarans and 1 % spirodienones). Direct 2D-NMR analysis of the hydrolyzed GL complex was not possible due to its low solubility. However, after sample acetylation, an even less condensed lignin than in the GML complex was found (with up to 72 % beta-O-4' substructures and only 1 % pinoresinols). The study provides evidence for the existence of structurally different lignins associated to hemicelluloses (xylan and glucomannan) and cellulose in spruce wood and, at the same time, offers information on some of the chemical linkages between the above polymers.

  • 26.
    Forsström, A
    et al.
    Eka Chemicals, Sweden.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Jour, P
    Eka Chemicals, Sweden.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    On selective removal of hexenuronic acid (HexA) by oxidative bleaching of eucalyptus O2-delignified kraft pulp2005Konferensbidrag (Refereegranskat)
  • 27.
    Gellerstedt, Göran
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    An HPLC method for the quantitative determination of hexeneuronic acid groups in chemical pulps1996Ingår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 294, s. 41-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has recently been demonstrated that 4-deoxy-L-threo-hex-4-enopyranosyluronic acid (''hexeneuronic acid'') is present in kraft pulps and linked to the xylan backbone. An analytical method for the quantitative determination of hexeneuronic acid groups has now been developed. The procedure involves a selective hydrolysis with mercuric acetate of the glucosidic linkage between the hexeneuronic acid group and the xylan chain, followed by oxidation with periodate to form P-formyl pyruvic acid. The latter is reacted with thiobarbituric acid, and the red-coloured adduct formed is separated by reverse phase HPLC and quantified by measuring the absorbance at 549 nm, Some kraft pulps have been analysed to illustrate the contribution of hexeneuronic acid groups to the total amount of oxidizable structures present in such pulps.

  • 28.
    Gellerstedt, Göran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Improved lignin properties and reactivity by modifications in the autohydrolysis process of aspen wood2005Konferensbidrag (Refereegranskat)
  • 29.
    Gellerstedt, Göran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lignin for material applications2009Konferensbidrag (Refereegranskat)
  • 30.
    Gellerstedt, Göran
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Xylan degradation products from birch kraft pulp1995Ingår i: Proceedings of the 8th International Symposium on Wood and Pulping Chemistry, Helsinki: Vol. I, 1995, s. 533-540Konferensbidrag (Övrigt vetenskapligt)
  • 31.
    Gellerstedt, Göran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Eide, Ingvar
    Kleinert, Mike
    Barth, Tanja
    Chemical Structures Present in Biofuel Obtained from Lignin2008Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 22, nr 6, s. 4240-4244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technical lignins from various sources can be converted into bio-oil with a low O/C ratio by pyrolysis in the presence of formic acid and an alcohol. By application of different analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and size-exclusion chromatography (SEC), it has been shown that a complete degradation of the lignin takes place irrespective of the origin. The resulting bio-oil has a low-molecular-mass distribution with a preponderance of aliphatic hydrocarbon structures. A substantial number of phenolic compounds are, however, also present, and some of these also contain carboxyl groups. The results clearly show that formic acid is a powerful supplier of atomic hydrogen. By further optimization of the pyrolysis reaction, it should be possible to further reduce the content of aromatic structures.

  • 32. Gosselink, Richard J. A.
    et al.
    van Dam, Jan E. G.
    de Jong, Ed
    Scott, Elinor L.
    Sanders, Johan P. M.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Fractionation, analysis, and PCA modeling of properties of four technical lignins for prediction of their application potential in binders2010Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, nr 2, s. 193-200Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Functional properties of technical lignins need to be characterized in more detail to become a higher added value renewable raw material for the chemical industry. The suitability of a lignin from different plants or trees obtained by different technical processes can only be predicted for selected applications, such as binders, if reliable analytical data are available. In the present paper, structure dependent properties of four industrial lignins were analyzed before and after successive organic solvent extractions. The lignins have been fractionated according to their molar mass by these solvents extractions. Kraft and soda lignins were shown to have different molar mass distributions and chemical compositions. Lignin carbohydrate complexes are most recalcitrant for extraction with organic solvents. These poorly soluble complexes can consist of up to 34% of carbohydrates in soda lignins. Modeling by principle component analysis (PCA) was performed aiming at prediction of the application potential of different lignins for binder production. The lignins and their fractions could be classified in different clusters based on their properties, which are structure dependent. Kraft soft-wood lignins show the highest potential for plywood binder application followed by hardwood soda lignin and the fractions of Sarkanda grass soda lignin with medium molar mass. Expectedly, the softwood lignins contain the highest number of reactive sites in ortho positions to the phenolic OH group. Moreover, these lignins have a low level of impurities and medium molar mass.

  • 33.
    Hassanzadeh, Masoumeh
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    TUNICATES FOR BIO MATERIALS PRODUCTION: EFFECTS OF DIFFERENT FACTORS ON CELLULOSE AND PROTEIN COMPOSITION2014Ingår i: PAPERS OF THE 22ND EUROPEAN BIOMASS CONFERENCE: SETTING THE COURSE FOR A BIOBASED ECONOMY, 2014, s. 1116-1123Konferensbidrag (Refereegranskat)
    Abstract [en]

    Tunicates, a group of marine animals, is gaining a lot of interests in case of medical, food market, water pollution, cellulosic nanomaterial, and biofuel production issues due to their consisting of chemical compounds such as cellulose, amino-sugars, and proteins or protein-polysaccharide complexes. In this work, two dominant species of Scandinavian tunicates have been investigated by extraction and characterization of their cellulose, and amino acids. Samples in different sizes, ages, place of growing (Distance to ocean's surface), and different chemical pretreatment, have been evaluated in their compositions to see the best conditions for extraction of cellulose and protein. For pure cellulose and bioethanol productions, the samples growing near to the ocean surface at the best harvesting time (after completion of metamorphosis), recommended to be explored. The highest amount of protein in tunicate body has been found in the internal organs with a total amino acid content of around 52 %. In addition, the larger and elder the sample is, the higher amount of protein it contains. Hence, for feed supplementing point of view, the internal organs of tunicates with higher size and age are favored to be considered. Eventually, a combination of both H3PO4 and Ba (OH)(2) might lead to a significantly high cellulose percentage (66.5%) and a high protein removal percentage (protein content of 6%) when aiming at cellulose extraction.

  • 34.
    Henriksson, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Shi, Chao
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    WAYS TO TAILOR-MAKE XYLAN FOR KRAFT PULPING2011Ingår i: 16TH INTERNATIONAL SYMPOSIUM ON WOOD, FIBER AND PULPING CHEMISTRY, PROCEEDINGS, VOLS I & II / [ed] Wang, L Kuang, S Hou, Q Cao, C Si, CL Zhang, HJ, CHINA LIGHT INDUSTRY PRESS , 2011, s. 596-599Konferensbidrag (Refereegranskat)
    Abstract [en]

    Genetic manipulation of trees in order to produce raw material with different chemical composition, which will perform better in pulping and bleaching, has gained large interest the last decade. Most efforts have been on increasing cellulose content, and modifying the lignin structure so that the pulping will be more efficient. Less interest has been focused on the hemicellulose structures, although many important chemical reactions occur on hemicelluloses during kraft pulping. For instance, hexenuronic acid is formed from 4-O-methyl glucuronic acid, a side group on xylan. This structure is a main contributor to the kappa number in the unbleached pulp, especially in hardwoods, and requires relatively strong bleaching agents for efficient removal. Remaining hexenuronic acid in the bleached pulp may furthermore cause post yellowing. In model experiments, we have simulated kraft cooking, and shown that hexenuronic acid is formed to a much lower degree from unmethylated glucuronic acid, than from 4-O-methylglucuronic acid. A tree without methyl groups on its glucuronic acid residues on xylan, is therefore expected to be pulped to a much lower kappa number, and to be easy to bleach to high brightness stability. According to a literature study, the possibilities to make such a tree by genetically manipulation appear to be promising. There might also be other ways, in which hemicelluloses structure can be manipulated.

  • 35.
    Henriksson, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Shi, Chao
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lindström, Mikael E
    Ways to tailor make xylan for kraft pulping2011Ingår i: : Proceedings of the 16th sInternational Symposium of wood, fiber and Pulp Chemistry, 2011, s. 596-599Konferensbidrag (Refereegranskat)
  • 36.
    Henriksson, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Zhang, Liming
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lignin Utilization2010Ingår i: Thermochemical conversion of biomass to liquid fuels and chemicals / [ed] M. Crocker, RSC Publishing, 2010, s. 222-262Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Lignin is one of the most abundant biopolymers on Earth, carrying out important biological roles in vascular plants. It has somewhat higher energy content than polysaccharides, but has a complex and heterogeneous structure including covalent bonds to polysaccharides. The partly random structure of lignin is explained by the fact that it is created by an uncatalyzed radical polymerization. Lignin is obtained as a by-product of various types of technical processes based on biomass, of which chemical pulping of wood is the most important. These technical lignins have structures that differ from native lignin. Sulphite pulping of wood generates a water soluble lignin derivate, which among other things, is used as a dispersing agent and dust binder. Kraft pulping generates a lignin that is insoluble at neutral pH, which today is mainly burned for heat generation in the chemical recovery system of the kraft pulp mill. Recently, efficient methods have been developed for the preparation of lignin from the process liquids, for use in energy generation or other applications. Conversion of technical lignin to liquid fuels for use in combustion engines is an interesting possibility that represents a technical challenge. This chapter reviews the structure and biopolymerisation of lignin, reactions of lignin during technical processes, and different applications of technical lignins.

  • 37.
    Henriksson, Gunnar
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Zhang, Liming
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Ljungquist, P.
    Reitberger, T.
    Pettersson, G.
    Johansson, G.
    Is cellobiose dehydrogenase from Phanerochaete chrysosporium a lignin degrading enzyme?2000Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology, ISSN 0167-4838, E-ISSN 1879-2588, Vol. 1480, nr 02-jan, s. 83-91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellobiose dehydrogenase (CDH) is an extracellular redox enzyme of ping-pong type, i.e. it has separate oxidative and reductive half reactions. Several wood degrading fungi produce CDH, but the biological function of the enzyme is not known with certainty. It can, however, indirectly generate hydroxyl radicals by reducing Fe3+ to Fe2+ and O-2 to H2O2. Hydroxyl radicals are then generated by a Fenton type reaction and they can react with various wood compounds, including lignin. In this work we study the effect of CDH on a non-phenolic lignin model compound (3,4-dimethoxyphenyl glycol). The results indicate that CDH can affect lignins in three important ways. (1) It breaks beta-ethers; (2) it demethoxylates aromatic structures in lignins; (3) it introduces hydroxyl groups in non-phenolic lignins. The gamma-irradiated model compound gave a similar pattern of products as the CDH treated model compound? when the samples were analyzed by HPLC, suggesting that hydroxyl radicals are the active component of the CDH system.

  • 38. Hilden, L.
    et al.
    Johansson, G.
    Pettersson, G.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Ljungquist, P.
    Henriksson, Gunnar
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Do the extracellular enzymes cellobiose dehydrogenase and manganese peroxidase form a pathway in lignin biodegradation?2000Ingår i: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 477, nr 02-jan, s. 79-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The extracellular enzyme manganese peroxidase is believed to degrade lignin by a hydrogen peroxide-dependent oxidation of Mn(II) to the reactive species Mn(III) that attacks the lignin, However, Mn(III) is not able to directly oxidise the non-phenolic lignin structures that predominate in native lignin, We show here that pretreatment of a non-phenolic lignin model compound with another extracellular fungal enzyme, cellobiose dehydrogenase, allows the manganese peroxidase system to oxidise this molecule. The mechanism behind this effect is demethoxylation and/or hydroxylation, i.e. conversion of a nonphenolic structure to a phenolic one, mediated by hydroxyl radicals generated by cellobiose dehydrogenase, This suggests that cellobiose dehydrogenase and manganese peroxidase may act in an extracellular pathway in fungal lignin biodegradation, Analytical techniques used in this paper are reverse-phase high-pressure liquid chromatography, gas chromatography connected to mass spectroscopy and UV-visible spectroscopy.

  • 39. Hou, Yi
    et al.
    Hu, Songqing
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Feasibility of monomer aromatic substances as calibration standards for lignin quantitative analyses in Pyrolysis-GCMS2013Ingår i: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 101, s. 232-237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, the feasibilities of five different monomer aromatic substances as calibration standards by analytical pyrolysis with gas chromatographic separation and mass selective detection (Py-GC/MS) were applied for the quantification of lignin in paper and pulp. The stabilities of these substances in the pyrolysis process were evaluated and the curves of peak response area to mass also were obtained. The results showed that the substances with exact same substitutions on the benzene ring as lignin units had good stabilities in the pyrolysis process with good lineabilities of peak response area to the mass curves, which implicated these substances can be applied as calibration standards in the liginin quick quantitative analyse without tedious pretreatments and structure changes.

  • 40.
    Jose Villaverde, Juan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ligero, Pablo
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    de Vega, Alberto
    Mild peroxyformic acid fractionation of Miscanthus x giganteus bark. Behaviour and structural characterization of lignin2012Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 35, nr 1, s. 261-268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Miscanthus x giganteus bark was subjected to mild fractionation with peroxyformic acid by a two stage process. A factorial experimental design was used to study and quantify the effect of the variables (formic acid concentration (80-90%), hydrogen peroxide concentration (0.2-0.4%), temperature of the first stage (60-80 degrees C), and treatment time of the second stage (60-120 min)) on the main parameters of fractionation: pulp yield, remaining lignin and total polysaccharides in pulp. The dependence of lignin precipitation rate on hydrogen peroxide concentration in liquor was also studied. Hydrogen peroxide concentrations inferior to 0.5% seems to be suitable to recover high percentages of lignin. The isolated lignin was analysed by 2D-HSQC, (13)C- and (31)P NMR spectroscopy, FTIR spectroscopy, size-exclusion chromatography and chemical analysis. The most important chemical modifications taken place in the lignin during the fractionation were identified: beta-O-4' cleavage and hydrolysis of LC-bond structures. The C9-formula was also determined: C(9)H(6.81)O(2.90)(OCH(3))(0.68)(COOH)(0.07)(OH(Ph))(0.38)(OH(Al))(0.33) .

  • 41.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    ON NATIVE AND ADVENTIVE LIGNIN-CARBOHYDRATE COMPLEX (LCC) STRUCTURES2010Ingår i: RESEARCH PROGRESS IN PAPER INDUSTRY AND BIOREFINERY (4TH ISETPP), VOLS 1-3, GUANGZHOU: SOUTH CHINA UNIV TECHNOLOGY PRESS , 2010, s. 328-331Konferensbidrag (Refereegranskat)
    Abstract [en]

    The LCC fractionation process developed by us has been further rationalized and successively applied for flax Soda-AQ pulps in demonstrating its universal applicability on all types of wood and non-wood species. The LCC characterization results revealed that native lignin is substantially attached at hemicelluloses, as xylan-lignin (accounted for 49% over the total amount of wood Klason lignin in eucalyptus and 20% in spruce) or as glucomannan-lignin (53% in spruce wood). As an example of adventive (manipulated) LCC structure, phenolic mediator-coupled xylan structure was identified at the xylan-lignin fraction prepared from laccase-mediator treated flax Soda-AQ pulps. The coupling took place between the mediator, lauryl gallate, and hexenuronic acid (HexA) at the intermediate layer in the pulps.

  • 42.
    Li, Jiebing
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Towards an accurate determination of lignin in chemical pulps: The meaning of kappa number as a tool for analysis of oxidable groups1999Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Lignin content is the most important parameter in chemicalpulping. At present, kappa number is the most common parameterfor determination of lignin content and the base for otheron-line methods and for industrial automation (Chapter 1). However, a substantial portion of the kappa number originates from non-lignin structures, for example from pulp xylan, whichhas been severely degraded and modified during the kraft cook (Chapter 2).

    During a systematic research about the hexenuronic acid (HUA) structure, one of the most important structures derivedfrom carbohydrates, a new, simple, fast and sensitivecolorimetric method has been developed for the quantificationof the HUA group (Chapter 3). Furthermore, it has been demonstrated that the quantitative contribution of the HUAgroups to the kappa number is 0.84-0.86 kappa units per 10µmol of HUA (Chapter 4).

    In systematic work about the reactions involved in the kappanumber determination, it was found that an addition of permanganate onto all the double bonds in the aromatic rings of lignin takes place, resulting in a reduction of permanganate toMnO2. The present standard method should therefore beimproved by rejecting or modifying the iodometric titrationmethod, correcting the concept of remaining permanganate, resetting the applicable region of permanganate consumption andshortening the reaction time (Chapter 5).

    The quantitative fundament for the kappa numberdetermination has been found to be a consumption of 11-12equivalents of KMnO4 per mole of C9units from any wood lignin structure. Besides HUA,any other non-lignin but oxidizable structure will, more or less, influence the accuracy of the kappa number determination;the most noticeable structures being double bonds, aldehydes orα-keto carboxylic acids (Chapter 6).

    Based on the above fundamental research, anoxymercuration-demercuration-kappa (Ox - Dem kappa) numberdetermination has been developed. All the noticeably interfering non-lignin structures are eliminated by one Ox -Dem procedure before a conventional kappa number determination so that a more accurate determination of aromatic (Klason) lignin content in pulps then can be easily, quickly and directly obtained (Chapter 7).

    For industrial and laboratory made unbleached chemicalpulps, it has been revealed that for different pine kraft orsoda pulps 2.9 - 4.8 kappa units were from non-ligninstructures, corresponding to 13-26% of the observed kappanumber. For birch kraft pulps, these data are much higher: 8.2-9.4 units, 60 - 80 % of the observed kappa number! Among these non-lignin contributions, approximately 30-60% are caused by HUA structure while the others are from double bonds, aldehydes or α-keto carboxylicacid structures, except forpine soda pulps where the non-lignin contributions are mainlyfrom the latter types of structures. Preliminary application ofthe Ox - Dem kappa number has resulted in brand new delignification curves for kraft cooking and OQP bleaching of birch pulp. A possible reformation of "lignin" in kraft cookingand a higher bleach-ability after low alkalinity and lowtemperature cooking have been noticed (Chapter 8).

    The easy and more accurate determination of lignin contentdescribed in this thesis suggests a promising future for better control of cooking and bleaching and for further optimizationand modification of present chemical pulping procedures.

  • 43.
    Li, Jiebing
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Danielsson, Sverker
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Kisara, Koki
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Quantification of uronic acid compositions by modification and integration of carbazole colorimetric and methanolysis-GC methodsManuskript (Övrigt vetenskapligt)
  • 44.
    Li, Jiebing
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Acid soluble lignin content in kraft pulps, an artifact2004Ingår i: 2nd International Symposium on Technologies Of Pulping, Papermaking and Biotechnology on Fiber Plants, Proceedings / [ed] Jin, YC; Xie, HF, NANJING: NANJING FORESTRY UNIV , 2004, s. 53-57Konferensbidrag (Refereegranskat)
    Abstract [en]

    Acid-soluble lignin (ASL) has been regarded as that part of the lignin in wood or pulp that dissolves in the acidic solution during Klason lignin determination. However, the absorption at 205 nm of the filtrate for the standard ASL determination cannot be considered as originating exclusively from lignin. Moreover, the standard method has been constructed only based on lignin models from woods, plants and semichemical bisulfite pulps, while is claimed to be universally applicable. In the present work, Kraft pulps from different wood species bleached using different sequences were subjected for the ASL determination and quantifications of different furan structures in the filtrate. It has been found that during the sulfuric acid hydrolysis, 20-30% and 70-80% of the hexenuronic acid in the pulp converts into 5-formyl-2-furancarboxylic acid and 2-furancarboxylic acid respectively. Both structures absorb substantially at 205 nm and account for up to 41% of the total absorption of the filtrate. On the other hand, furfural and hydroxymethyl furfural, decomposed from hemicellulose and cellulose respectively, account for a further up to 8.7% of the total absorption. Considering also other non-lignin structures in the filtrate which absorb 205 nm, we conclude that the existence of native and modified carbohydrates makes the ASL determination meaningless for Kraft pulps.

  • 45.
    Li, Jiebing
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Improved lignin properties and reactivity by modifications in the autohydrolysis process of aspen wood2008Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 27, nr 2, s. 175-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autohydrolysis of aspen wood breaks down lignin beta-O-4 linkages via both acidolysis and homolytical cleavage. A simultaneous repolymerization by lignin-lignin condensation is the major reason for the low degree of delignification and the poor lignin reactivity. Modification of the autohydrolysis reaction by the addition of either NaOH or 2-naphthol changes the mechanism such that less acidolysis and fewer lignin-lignin condensation reactions take place, and an almost complete delignification can be achieved. The resulting isolated lignins have a low M., a light color and still contain some of the native beta-O-4 linkages. Lignin from autohydrolysis in the presence of NaOH possesses more carboxylic acid groups, while the addition of 2-naphthol results in a lignin with a large amount of phenolic hydroxyl groups and incorporated naphthalene rings. These types of change are beneficial since the lignin structure becomes much more homogeneous with a greater potential for further upgrading and use.

  • 46.
    Li, Jiebing
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Kinetics and mechanism of kappa number determination1998Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 13, nr 2, s. 147-152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetics and mechanism involved in the kappa number determination have been studied using a spectrophotometric method to monitor the oxidation of pine kraft pulp as well as of model compounds for lignin and carbohydrates. It was found that, during the kappa number determination, the permanganate oxidation proceeds stepwise, forming manganese dioxide which is then reduced to manganous ions. Lignin is oxidized by the addition of permanganate to all the double bonds in the aromatic rings followed by a rupture of the rings. The predominant part of the oxidation of lignin is completed within one minute whereas the oxidation of e.g. glucose is slow but proceeds at an accelerating rate during the kappa number determination time (10 min). The spectrophotometric determination of per manganate remaining after the reaction has advantages over the traditional iodometric method.

  • 47.
    Li, Jiebing
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    On the structural significance of the kappa number measurement1998Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 13, nr 2, s. 153-158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structural significance of a kappa number has been studied by quantifying the permanganate consumption of various isolated pine, birch and poplar lignins, of lignin model compounds and of carbohydrate and other aliphatic compounds under kappa number measurement conditions. It was found that the average permanganate consumption for the different lignins was 11-12 equivalents per phenylpropane unit. This value is in accordance with the addition of permanganate ion to all three double bonds in the aromatic rings regardless of whether these are phenolic or non-phenolic or whether they belong to a guaiacyl or a syringyl unit. It was further found that permanganate can be consumed by other types of oxidizable structures like aliphatic double bonds, aldehyde groups and alpha-keto-carboxylic acid groups. For unbleached kraft pulp samples, the combined consumption of permanganate by lignin and hexenuronic acid groups from xylan was found to be fairly close to the measured kappa number. The small discrepancies found indicate, however, that other types of structures may contribute to the kappa number.

  • 48.
    Li, Jiebing
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Oxidative damage of pulp cellulose during different bleaching operations2006Ingår i: Research Progress in Pulping and Papermaking, 2006 / [ed] Beihai, H; Shiya, F; Fangeng, C, 2006, s. 315-320Konferensbidrag (Refereegranskat)
    Abstract [en]

    An oxidative damage at pulp cellulose is not desirable but unavoidable during pulp bleaching. The oxidation at C-6 hydroxyl group results in a formation of C6-aldehyde and/or C6-carboxyl (glucuronic acid) structure. There is however not a simple and routine method available for quantification of the oxidised structures. In the present paper, methanolysis after a 72% sulphuric acid pre-solubilisation in combination of acetylation followed by GC-MS has been set up for quantification of the uronic acid structures in cellulose. Industrial birch and spruce kraft pulps were analysed after each oxidation operation in TCF and ECF bleaching sequence respectively. It was concluded that C6 carboxyl group exist in all the pulps tested. Oxygen delignification and (PO) stage generates more glucuronic acid structure in the softwood and the hardwood respectively. Galacturonic acid content was also increased during oxygen delignification of the spruce kraft pulp.

  • 49.
    Li, Jiebing
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Oxymercuration-demercuration kappa number: An accurate estimation of the lignin content in chemical pulps2002Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, nr 4, s. 410-414Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the kappa number determination, it has been found that non-lignin structures contribute to the consumption of permanganate, and thus make it difficult to estimate the lignin content in the pulp. In order to improve the accuracy of the determination, a two-step pretreatment with mercury acetate - sodium borohydride prior to a conventional kappa number determination is proposed. It has been found that such a pretreatment eliminates all interfering structures in the pulp except a, P-unsaturated carboxylic acid groups. and thus permits a very accurate estimation of the lignin content. The method has been termed "oxymercuration - demercuration (Ox-Dem) kappa number" and can be used to obtain information not only about the lignin content but also about the quantity of other oxidizable structures present in a chemical pulp. New information concerning the delignification reactions taking place in pulping and bleaching can thus be obtained.

  • 50.
    Li, Jiebing
    et al.
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Rapid and direct pulp kappa number determination using spectrophotometry - Comments2001Ingår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, nr 4, s. 111-111Artikel i tidskrift (Refereegranskat)
123 1 - 50 av 107
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