| 1. |
- Hafrén, Johan, et al.
(författare)
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Distribution of acidic and esterified polygalacturonans in sapwood of spruce, birch and aspen
- 2001
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 16:4, s. 284-290
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Tidskriftsartikel (refereegranskat)abstract
- The distribution and degree of esterification of polygalacturonans have been studied in spruce, birch and aspen using immunolocalization. Monoclonal antibodies against acidic and methyl esterified polygalacturonan were localized by fluorescence- and transmission electron microscopy.
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| 2. |
- Hafrén, Jonas, et al.
(författare)
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Formation of 13C-enriched cell-wall DHP using isolated soft xylem from Picea abies
- 2002
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 56:6, s. 585-591
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Tidskriftsartikel (refereegranskat)abstract
- Cell-wall dehydrogenation polymers (CW-DHP) were prepared by incubating a mixture of soft xylem (differentiating xylem) from Picea abies, coniferin 13C-enriched at the side-chain β-carbon and unenriched coniferin, both with and without the addition of β-glucosidase and glucose oxidase, which causes an in situ polymerisation of the coniferyl alcohol in the cell wall. From difference solid state 13C-NMR spectra between 13C-enriched CW-DHP and unenriched CW-DHP, the bond frequencies involving specifically 13C-enriched carbon can be quantitatively determined. The sub-structures in CW-DHP prepared without the addition of β-glucosidase and glucose oxidase showed more similarity to protolignin than CW-DHP prepared with the addition of extraneous enzymes. The CW-DHP obtained without the addition of enzymes contained 36% β-O-4-derived sub-structures, 44% combined β-β, β-5 and β-1 sub-structures and 20% coniferyl alcohol/coniferaldehyd end groups. After acetone/water extraction of the CW-DHP, the content of β-β, β-5 and β-1 structures decreased by 4%, and the β-O-4 dominating peak increased by 4%. The 13C-enriched CW-DHP material can be used to study lignin reactions in a solid wood matrix, and is also a powerful system for detailed studies on in vivo lignification mechanisms and the effects on lignification conditions on lignin structure.
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| 3. |
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| 4. |
- Hafrén, Jonas, et al.
(författare)
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The distribution of acidic and esterified pectin in cambium, developing xylem and mature xylem of Pinus sylvestris
- 2000
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Ingår i: IAWA Journal. - : Brill. - 0928-1541 .- 2294-1932. ; 21:2, s. 157-168
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Tidskriftsartikel (refereegranskat)abstract
- Homogalacturonans with low and high degree of methyl esterification have been immuno-localised in the cambium, differentiating xylem and mature xylem of Pinus sylvestris, by monoclonal antibodies JIM5 and JIM7. In the unlignified cambial tissue the antibodies revealed a similar distribution for acidic and esterified pectin in the compound middle lamella, ray cell walls and pit membranes. In the lignified xylem tissue, pectin was also found in the compound middle lamella, although dominantly in the methylesterified form. Lignification seemed to coincide with a decrease in the presence of acidic pectin in the compound middle lamella. Both antibodies indicated labelling in pit membranes and ray cell walls in partially and fully lignified wood fibres.
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| 5. |
- Hafrén, Jonas, et al.
(författare)
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Ultrastructural changes in the compound middle lamella of Pinus thunbergii during lignification and lignin removal
- 2000
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:3, s. 234-240
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the middle lamella in Pinus thunbergii has been studied by the rapid-freeze deep-etching (RFDE) technique in combination with transmission electron microscopy (TEM). The ultrastructure of the compound middle lamella was studied in the early phases of the development of woody tissue in the cambial and differentiating xylem, before the heavy incrustation with lignin had occurred. Lignified middle lamella in the xylem was studied both directly and after delignification. It was found that the structure of the unlignified middle lamella in the cambium/developing xylem consists of a fine irregular network probably containing pectin and hemicellulose. As a result of lignin incrustation, the middle lamella becomes increasingly dense and the surface structure of the fully lignified middle lamella appeared to be compact and partly covered with globular structures. After delignification of the lignified middle lamella a thin network with a different structure was revealed. This network probably mainly consists of hemicellulose. No microfibrils of the type that occurs in the primary and secondary walls were found in the middle lamella.
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| 6. |
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| 7. |
- Karlsson, Olov, et al.
(författare)
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Environmentally friendly process for high density fibreboards
- 2006
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Urea-formaldehyde (UF) resin is a common binder in many fibre- and particleboards today. However, formaldehyde is a fairly reactive compound with many negative affects on health and environment. This paper describes a process to make thin high density fibreboards without use of conventional resin such as UF. Initially we found that wood particles such as ones used in particle board had, when activated with hydrogen peroxide and iron catalyst, self-bonding capability when hot-pressed into boards. Low swelling board, although at somewhat higher density than conventional glued ones, could be formed by pressing activated wood particles at 170 oC in a laboratory press. We found that the activation technique was applicable to dry or semi-dry board processes and was considered to be well suited for fibreboards from refined wood fibers especially as their specific (contact) area is high. Activated wood fibres were produced at Metso Panelboards Pilot-refiner in Sundsvall and mats were also formed and pressed into boards 50x60 cm2 at fairly conventional pressing conditions. At a hydrogen peroxide charge of 4% boards made from birch fibres with good mechanical properties (in terms of bending strength and internal bonding) were produced. Thickness swelling in water was low (TS24h., 15-20%). At lower hydrogen peroxide charges (<2%) the swelling was higher. Development of the process to also include other wood species than birch is in our interest. Furthermore, properties of the boards were strongly dependent on the moisture content of fibres; at low moisture content (MC<8%) thickness swelling increased. We see a high potential in the process as the glue-free technique is estimated to reduce production cost of boards as well as give environmental advantages.
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| 8. |
- Karlsson, Olov, et al.
(författare)
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Evidence for chemical bonds between lignin and cellulose in kraft pulps
- 1996
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 22:10, s. J397-401
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Tidskriftsartikel (refereegranskat)abstract
- The cellulose solvent system LiCl-dimethylacetamide has been used to dissolve kraft pulps prepared from pine and birch. The dissolved polymers were analyzed using size-exclusion chromatography combined with both RI- and UV-detection systems in order to monitor simultaneously the major wood polymers (cellulose, hemicellulose and lignin). Kraft pulps from birch were completely soluble in the solvent system and the pine kraft pulp about 80% soluble. Analyses of the kraft pulps strongly suggest that a considerable amount of the residual lignin is chemically linked to the high molecular weight cellulose in pine but not in birch. The presence of stable lignin-cellulose bonds will reduce the possibility of achieving a low kappa number by cooking. For comparison, sulphite and bisulphite pulps were also examined. Both pulps were soluble in the solvent system and analyses indicated that lignin-cellulose bonds also exist in these pulps although to a significantly lesser extent than in the pine kraft pulp
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| 9. |
- Karlsson, Olov, et al.
(författare)
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Linkages between residual lignin and carbohydrates in bisulphite (magnefite) pulps
- 2001
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:9, s. 310-316
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Tidskriftsartikel (refereegranskat)abstract
- The presence of bonds between residual lignin and carbohydrates in bisulphite pulps from hardwoods and softwoods was studied. Results showed that a fraction of the residual lignin was bonded to cellulose in bisulphite pulps of softwood. The treatment with xylanase indicated the existence of alkali-stable lignin-xylan bonds in softwood bisulphite pulps.
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| 10. |
- Karlsson, Olov, et al.
(författare)
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Resin-free particleboard by oxidation of wood
- 2002
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Ingår i: 6th Pacific Rim Bio-Based Composites Symposium & Workshop on the Chemical Modification of Cellulosics. - Corvallis, Or : Wood science and engineering department.
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Konferensbidrag (refereegranskat)
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