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  • 1. Eguees, Itziar
    et al.
    Stepan, Agnes M.
    Eceiza, Arantxa
    Toriz, Guillermo
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Gothenburg, Sweden.
    Labidi, Jalel
    Corncob arabinoxylan for new materials2014Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 102, s. 12-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Corncob agricultural waste was used as a source of arabinoxylan for preparation of films. Three arabinoxylan samples were prepared: crude extract (CCAX), purified by a washing step, and purified by bleaching CCAX. Films prepared with untreated CCAX were water soluble, yellowish in color and had poor mechanical properties. After the purification processes the Young's modulus increased from similar to 293 MPa to similar to 1400-1600 MPa, and strength was improved from similar to 9 MPa to around 53 MPa, while the strain at break was kept at similar to 8% both in untreated and purified CCAX. The contact angle was increased from similar to 21.3 degrees to 67-74 degrees after washing or bleaching CCAX. Acetylation of bleached CCAX showed the highest thermal resistance (325 degrees C), had low T-g (125 degrees C) and a high contact angle (80 degrees), and its films were stronger (strength similar to 67 MPa; Young's modulus similar to 2241 MPa) and more flexible (similar to 13%). These characteristics make purified CCAX a suitable material to be used as a matrix for film applications.

  • 2. Escalante, Alfredo
    et al.
    Goncalves, Ana
    Bodin, Aase
    Stepan, Agnes
    Sandstrom, Corine
    Toriz, Guillermo
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Chalmers, Sweden.
    Flexible oxygen barrier films from spruce xylan2012Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 87, nr 4, s. 2381-2387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Arabinoglucuronoxylan was extracted from Norway spruce and films prepared by casting from aqueous solution. The sugar analysis and NMR confirmed that the spruce xylan was composed of arabinose, 4-O-methyl-glucuronic acid and xylose in a ratio of 1:2:11 respectively. Substitutions of 4-O-methyl-alpha-D-GlcpA at O-2 and of alpha-L-Araf at O-3 on the xylose backbone were found by NOE analysis. NOE cross-peaks indicated as well that there is at least one free xylose on the main chain present between two substitutions. Whether the distribution of side chains was random or in blocks was uncertain. The average molecular weight of the sample was determined by size exclusion chromatography to be 12,780 g/mol. Arabinoglucoronoxylan casting yielded transparent flexible films with an average stress at break of 55 MPa, strain at break of 2.7% and a Young's Modulus 2735 MPa. Wide-angle X-ray scattering analysis showed that the arabinoglucuronoxylan films were totally amorphous. Addition of sorbitol as plasticizer resulted in less strong but more flexible films (strain at break of 5%). Peaks of crystallinity could be seen in X-ray which corresponds to sorbitol crystallizing in distinct phases. The dynamic mechanical analysis showed that the arabinoglucuronoxylan film softened at a later relative humidity (80% RH) in comparison with plasticized films (60% RH). The films showed low oxygen permeability and thus have a potential application in food packaging.

  • 3.
    Gatenholm, Paul
    et al.
    Wallenberg Wood Sci Ctr, Dept Chem & Biol Engn, Sweden.
    Martinez, Hector
    Sundberg, Johan
    Bioprinting of 3D porous nanocellulose scaffolds for tissue engineering and organ regeneration2012Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikel i tidskrift (Övrigt vetenskapligt)
  • 4. Kiemle, Sarah N.
    et al.
    Zhang, Xiao
    Esker, Alan R.
    Toriz, Guillermo
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Gothenburg, Sweden.
    Cosgrove, Daniel J.
    Role of (1,3)(1,4)-beta-Glucan in Cell Walls: Interaction with Cellulose2014Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, nr 5, s. 1727-1736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    (1,3)(1,4)-beta-D-Glucan (mixed-linkage glucan or MLG), a characteristic hemicellulose in primary cell walls of grasses, was investigated to determine both its role in cell walls and its interaction with cellulose and other cell wall polysaccharides in vitro. Binding isotherms showed that MLG adsorption onto microcrystalline cellulose is slow, irreversible, and temperature-dependent. Measurements using quartz crystal microbalance with dissipation monitoring showed that MLG adsorbed irreversibly onto amorphous regenerated cellulose, forming a thick hydrogel. Oligosaccharide profiling using endo-(1,3)(1,4)-beta-glucanase indicated that there was no difference in the frequency and distribution of (1,3) and (1,4) links in bound and unbound MLG. The binding of MLG to cellulose was reduced if the cellulose samples were first treated with certain cell wall polysaccharides, such as xyloglucan and glucuronoarabinoxylan. The tethering function of MLG in cell walls was tested by applying endo-(1,3)(1,4)-beta-glucanase to wall samples in a constant force extensometer. Cell wall extension was not induced, which indicates that enzyme-accessible MLG does not tether cellulose fibrils into a load-bearing network.

  • 5. Kuzmenko, Volodymyr
    et al.
    Hagg, Daniel
    Toriz, Guillermo
    Gatenholm, Paul
    In situ forming spruce xylan-based hydrogel for cell immobilization2014Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 102, s. 862-868Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An in situ forming spruce xylan-based hydrogel was synthesized in two steps with the intended use of cell encapsulation and in vivo delivery. First, bioconjugate was obtained through the reaction of glucuronic acid groups from xylan backbone with tyramine (TA). After that, the gelation process was enabled by enzymatic crosslinking of the phenol-containing TA-xylan conjugate. Exhibiting an exponential increase in the storage modulus, a 3D gel network was formed in about 20s. The designed gel showed extensive swelling and retained its mechanical integrity for more than two months. Mesenchymal stem cells were encapsulated in the hydrogel and cultured for one week. The cells retained their adipogenic differentiation capacity inside the gel, as verified by lipid accumulation. From these facts, we conclude that spruce xylan is a promising precursor for in situ forming hydrogels and should be evaluated further for tissue engineering purposes.

  • 6. Sundberg, Johan
    et al.
    Toriz, Guillermo
    Gatenholm, Paul
    Wallenberg Wood Science Center, Göteborg, Sweden .
    Moisture induced plasticity of amorphous cellulose films from ionic liquid2013Ingår i: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 54, nr 24, s. 6555-6560Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Amorphous cellulose films were created by regeneration from 1-Ethyl-3-methylimidazolium acetate (EmimAc) solutions. Their mechanical properties were analyzed as a function of water content. Cellulose with different molecular weights, i.e. microcrystalline cellulose (Avicel), Spruce cellulose and bacterial nanocellulose (BNC), were used for film preparation. All the regenerated films were free from EmimAc residues as shown by Fourier transform infrared spectroscopy (FTIR), amorphous as shown by wide angle X-ray spectroscopy (WAXS) and optical transparent. The equilibrium water content (w/w) was measured at different relative humidities. The plasticizing effect of water on the films was evidenced by both tensile tests and dynamical mechanical analysis (DMA) with humidity scans. The mechanical properties were clearly related to the proportional water uptake of the films. The sample with the longest cellulose chains, i.e. BNC, showed significantly larger elongation to brake at high moisture content which was owed to chain entanglements.

  • 7. Thunberg, Johannes E.
    et al.
    Westman, Gunnar
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Chalmers, Sweden.
    Cellulose nanofibers electrospun from non volatile ionic liquid2012Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikel i tidskrift (Övrigt vetenskapligt)
  • 8.
    Zhang, Yujia
    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.
    Stepan, Agnes
    Gatenholm, Paul
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers University of Technology, Göteborg.
    Spruce glucomannan: Preparation, structural characteristics and basic film forming ability2013Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, nr 3, s. 323-330Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study one representative hemicellulose in spruce wood, low galactosyl substituted glucomannan (GM), has been prepared and purified from holocellulose by NaOH/H3BO4 extraction, Fehling reagent precipitation and HCl regeneration. The GM structure obtained was comprehensively characterized by FTIR, hydrolysis-IC, SEC, and various solution- and solid state NMR spectroscopies. In addition, two pretreatment methods have been evaluated to form films from the GM. It was found that the spruce GM is composed of galactose, glucose and mannose in a ratio of 0.03:1:3.4. The molecular masses are around 255 kDa (Mw) against pullulan standards. The GM was almost free from other polysaccharides such as xylan (0.61%) and free from metal ions (<0.2% ash content). After blending with glycerol or pre-acetylation, two yellowish transparent films have been obtained after solution casting. For the former, water affinity was observed while for the latter water resistance was noticed. Potential high value applications of this GM include packaging and coatings in food and pharmaceutical industry.

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