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  • 1.
    Adu, Cynthia
    et al.
    Manufacturing and Materials Department, Cranfield University.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Eichhorn, Stephen J.
    Bristol Composites Institute (ACCIS), Queens Building, School of Engineering, Bristol University.
    Jolly, Mark
    Manufacturing and Materials Department, Cranfield University.
    Zhu, Chenchen
    Bristol Composites Institute (ACCIS), Queens Building, School of Engineering, Bristol University.
    Properties of cellulose nanofibre networks prepared from never-dried and dried paper mill sludge2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 197, no 1, p. 765-771Article in journal (Refereed)
    Abstract [en]

    Paper mills yield large volumes of sludge materials which pose an environmental and economic challenge for disposal, despite the fact that they could be a valuable source for cellulose nanofibres (CNF) production. The aim of the study was to evaluate the production process and properties of CNF prepared by mechanical fibrillation of never-dried and dried paper mill sludge (PMS). Atomic force microscopy (AFM) showed that average diameters for both never-dried and dried paper sludge nanofibres (PSNF) were less than 50 nm. The never-dried and dried sludge nanofibres showed no statistical significant difference (p > 0.05) in strength 92 MPa, and 85 MPa and modulus 11 GPa and 10 GPa. The study concludes that paper mill sludge can be used in a dried state for CNF production to reduce transportation and storage challenges posed on industrial scale.

  • 2.
    Agarwal, Parminder
    et al.
    Michigan State University.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of polymeric additives on calcium carbonate crystallization as monitored by nephelometry2004In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 4, no 3, p. 479-483Article in journal (Refereed)
    Abstract [en]

    The effect of polymaleimide polymers on calcium carbonate crystallization was studied using nephelometry. Induction time and percent growth inhibition were determined for polymeric additives from the nephelometric data. The polymaleimide synthesized by KOH-initiated polymerization exhibited the greatest growth inhibition and longest nucleation time among the polymers investigated. Raman spectroscopy was used to determine the calcium carbonate polymorph formed in the presence of these polymeric additives.

  • 3.
    Agarwal, Parminder
    et al.
    Michigan State University.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    In situ monitoring of calcium carbonate polymorphs during batch crystallization in the presence of polymeric additives using Raman spectroscopy2003In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 3, no 6, p. 941-946Article in journal (Refereed)
    Abstract [en]

    Polycarboxylic acids are well-known to affect calcium carbonate crystallization. Agarwal et al. (Ind. Eng. Chem. Res. 2003, in press) reported previously the synthesis of polymaleimide by a variety of techniques and initiators. In the present work, the effect of these polymers on calcium carbonate crystallization was studied by a variety of techniques. Crystallization experiments were carried out in a 1-L LABMAX automated batch reactor, and the concentration of calcium in solution was determined in real time. Raman spectroscopy was used to determine the relative amount of various calcium carbonate polymorphs as the crystallization occurred. However, Raman spectroscopy is a scattering technique, which may make it surface selective, and therefore results from solids may not be representative of bulk of sample. X-ray diffraction (XRD) was used to compare the results obtained by Raman spectroscopy. Peak intensity ratios were used for both Raman spectroscopy and XRD for calibration and measurement purposes. The results obtained by these two techniques for final percent vaterite for calcium carbonate crystallization in the presence of polymeric additives were in agreement within 2%. Therefore, use of Raman spectroscopy for in situ measurement of polymorph composition during calcium carbonate crystallization appears accurate. Scanning electron microscopy (SEM) data were useful in understanding the crystal morphology and to determine crystal size.

  • 4.
    Agarwal, Parminder
    et al.
    Michigan State University.
    Yu, Qiuyue
    Michigan State University.
    Harant, Adam
    Michigan State University.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Synthesis and characterization of polymaleimide2003In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 42, no 13, p. 2881-2884Article in journal (Refereed)
    Abstract [en]

    Simplified syntheses of polymaleimide employing anionic polymerization (from the melt and from solution) and metal compound-alcohol initiators such as PbO, SnO, tin bis(2-ethyl hexanoate) in the presence of tert-butyl benzyl alcohol are presented. The resulting polymers contain a combination of C-N- and C-C-connected monomers. Preliminary structures of the polymers were determined using NMR spectroscopy. The ratio of C-N- and C-C-connected monomers was determined, and the percentage of C-N-connected monomer units was found to vary from 40 to 80%, with the higher percentage resulting from anionic polymerization. The molecular weights of the polymers, as determined by gel permeation chromatography (GPC) with aqueous mobile phase and sodium polyacrylates standards, ranged between 1100 and 4200 for anionic polymerization and were about 11 500 for metal oxide-alcohol initiated polymerization. Solution-phase properties of the polymaleimides were evaluated by calcium chelation and precipitation inhibition studies. On the basis of the measured properties of these polymers, they are proposed as biodegradable, low-impact detergent additives to substitute currently used compounds.

  • 5.
    Ahlén, Gustaf
    et al.
    Recopharma AB.
    Strindelius, Lena
    Recopharma AB.
    Johansson, Tomas
    Recopharma AB.
    Nilsson, Anki
    Rrecopharma AB.
    Chatzissavidou, Nathalie
    Recopharma AB.
    Sjöblom, Magnus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holsgersson, Jan
    Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy.
    Mannosylated mucin-type immunoglobulin fusion proteins enhance antigen-specific antibody and T lymphocyte responses2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 10Article in journal (Refereed)
    Abstract [en]

    Targeting antigens to antigen-presenting cells (APC) improve their immunogenicity and capacity to induce Th1 responses and cytotoxic T lymphocytes (CTL). We have generated a mucin-type immunoglobulin fusion protein (PSGL-1/mIgG2b), which upon expression in the yeast Pichia pastoris became multivalently substituted with O-linked oligomannose structures and bound the macrophage mannose receptor (MMR) and dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) with high affinity in vitro. Here, its effects on the humoral and cellular anti-ovalbumin (OVA) responses in C57BL/6 mice are presented.OVA antibody class and subclass responses were determined by ELISA, the generation of anti-OVA CTLs was assessed in 51Cr release assays using in vitro-stimulated immune spleen cells from the different groups of mice as effector cells and OVA peptide-fed RMA-S cells as targets, and evaluation of the type of Th cell response was done by IFN-γ, IL-2, IL-4 and IL-5 ELISpot assays.Immunizations with the OVA − mannosylated PSGL-1/mIgG2b conjugate, especially when combined with the AbISCO®-100 adjuvant, lead to faster, stronger and broader (with regard to IgG subclass) OVA IgG responses, a stronger OVA-specific CTL response and stronger Th1 and Th2 responses than if OVA was used alone or together with AbISCO®-100. Also non-covalent mixing of mannosylated PSGL-1/mIgG2b, OVA and AbISCO®-100 lead to relatively stronger humoral and cellular responses. The O-glycan oligomannoses were necessary because PSGL-1/mIgG2b with mono- and disialyl core 1 structures did not have this effect.Mannosylated mucin-type fusion proteins can be used as versatile APC-targeting molecules for vaccines and as such enhance both humoral and cellular immune responses.

  • 6.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood2013In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, no 3, p. 499-513Article in journal (Refereed)
    Abstract [en]

    Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170°C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.

  • 7.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives2012In: Wood and Fiber Science, ISSN 0735-6161, Vol. 44, no 1, p. 85-93Article in journal (Refereed)
    Abstract [en]

    An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.

  • 8.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cloutier, Alain
    Wood Research Center (CRB), Department of Wood and Forest Sciences, Faculty of Forestry, Geography and Geomatics, Laval University, Quebec.
    Fang, Chang-Hua
    Wood Research Center (CRB), Department of Wood and Forest Sciences, Faculty of Forestry, Geography and Geomatics, Laval University, Quebec.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 24, p. 8571-8579Article in journal (Refereed)
    Abstract [en]

    Approximately, 13.5 % of the standing volume of productive forest land in Sweden is covered by birch and aspen, which provides the vast potential to produce value-added products such as densified wood. This study shows whether it is possible to densify those species with a thermo-hygro-mechanical (THM) process using heat, steam, and pressure. In this process, transverse compression on thin European aspen (Populus tremula) and downy birch (Betula pubescens) boards was performed at 200 ºC with a maximum steam pressure of 550 kPa. To obtain a theoretical 50 % compression set, the press’s maximum hydraulic pressure ranged from 1.5 to 7.3 MPa. Preliminary tests showed that ~75 % of the birch boards produced defects (blisters/blows) while only 25 % of the aspen boards did. Mainly, radial delamination associated with internal checks in intrawall and transwall fractures caused small cracks (termed blisters) while blows are characterized by relatively larger areas of delamination visible as a bumpy surface on the panel. Anatomical investigations revealed that birch was more prone to those defects than aspen. However, those defects could be minimized by increasing the pre-treatment time during the THM processing.

  • 9.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy2013In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, no 1, p. 57-66Article in journal (Refereed)
    Abstract [en]

    The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

  • 10. Ahmed, Sheikh Ali
    et al.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 251-258Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in uneven distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 11.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Development of a new rapid method for mould testing in a climate chamber: Preliminary tests2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 4, p. 451-461Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12-14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.

  • 12.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood: Impact of drying, thermal modification, and copper-based preservative2013In: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 85, p. 284-288Article in journal (Refereed)
    Abstract [en]

    The development of mould on wood surfaces depends on several factors. Although mould does not affect the mechanical properties of wood, it greatly reduces the aesthetic value of wood like the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are also a great concern. Different types of dried and treated wood were used to observe whether they had enhanced durability against mould following an accelerated laboratory test method in a climate chamber. Samples were green, air-dried, industrially thermally-modified, treated with copper-based preservative, and kiln-dried wood, which were tested within a single test run. The test produced the following main results: the thermal modification increased the durability of the wood, and the protective effectiveness of alternative treatments was comparable to that of commercially available copper-based treatment. However, the initial moisture content of the samples during mould exposure had a great influence on the onset of mould growth. The risk of mould susceptibility of industrial kiln-dried lumber can be reduced by drying using the double-layering technique which likely forced the nutrients to deposit near the evaporation surfaces followed by planing off the nutrient enriched edges.

  • 13.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Yang, Qian
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Accelerated mold test on dried pine sapwood boards: Impact of contact heat treatment2013In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, no 3, p. 174-187Article in journal (Refereed)
    Abstract [en]

    We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ‘‘sapwood out’’ and ‘‘sapwood in’’ positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). Accelerated mold test was performed in a climate chamber where naturally mold infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides which accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth was 170°C for 10 min. But, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.

  • 14. Aimi, H.
    et al.
    Matsumoto, Y.
    Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo.
    Meshitsuka, G,
    Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo.
    Endwise type lignin present as small lignin fragments linked to carbohydrate2005In: Chemistry and performance of composites containing wood and natural plant fibres: pre-symposium [of] 59th APPITA annual conference and exhibition, incorporating 13th ISWFPC, International Symposium on Wood, Fibre and Pulping Chemistry : Rotorua, New Zealand, 12 - 13 May 2005 ; proceedings, Carlton, VIC: Appita , 2005, p. 427-430Conference paper (Refereed)
    Abstract [en]

    The content of glyceraldehyde-2-aryl ether type structure in water soluble LCC fractions, which was obtained from Japanese cedar and birch residual wood meal after MWL isolation, was determined by the use of ozonation method. Quite high amount of glyceraldehyde-2-aryl ether type structure was found in water soluble LCC fractions of both species, which was about 3-5 times higher than that of other fractions. This result as well as the high content of β-1 structure in these fractions shown in our previous papers suggest that lignin in these fractions has characteristics as endwise type lignin, because abundance of both of these structures are typical for this type of lignin. These results are in good accordance with the generally accepted hypothesis that glyceraldehyde-2-aryl ether type structure and β-1 structure are generated at the same time by radical coupling reaction. It was also indicated that these two structures are present very close to each other in lignin

  • 15.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Allard, Christina
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Lin, Janet
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Sandström, Anders
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    LTU Teaching guide to e-learning: how to clear the mist of teaching through the cloud2015Conference paper (Other academic)
  • 16.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Linder, Tomas
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Light scattering in cellulose nanofibre suspensions: Model and experiments2016In: Computers in Chemistry Proceeding from ACS National Meeting San Diego: Proceeding from ACS National Meeting San Diego, American Chemical Society (ACS), 2016, p. 122-, article id CELL 235Conference paper (Other academic)
    Abstract [en]

    Here light scattering theory is used to assess the size distribution in a suspension of cellulose as it is fibrillated from micro-scaled to nano-scaled fibres. A model based on Monte carlo simulations of the scattering of photons by different sizes of cellulose fibres was used to predict the UV-IF spectrum of the suspensions. Bleached cellulose hardwood pulp was tested and compared to the visually transparent tempo-oxidised hardwood cellulose nanofibres (CNF) suspension. The theoretical results show that different diameter size classes exhibit very different scattering patterns. These classes could be identified in the experimental results and used to establish the size class dominating the suspension. A comparison to AFM/microscope size distribution was made and the results indicated that using the UV-IF light scattering spectrum maybe more reliable that size distribution measurement using AFM and microscopy on dried CNF samples. The UV-IF spectrum measurement combined with the theoretical prediction can be used even at this initial stage of development of this model to assess the degree of fibrillation when processing CNF.

  • 17.
    Aitomäki, Yvonne
    et al.
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Hagström, Bengt
    SWEREA IVF AB.
    Långström, Runar
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Fernberg, Patrik
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Novel reactive bicomponent fibres: Material in composite manufacturing2012In: Journal of Nanostructured Polymers and Nanocomposites, ISSN 1790-4439, Vol. 8, no 1, p. 5-11Article in journal (Refereed)
    Abstract [en]

    The hypotheses that reactive uncured, thermoset bicomponent fibres can be prepared and mixed with reinforcing fi- bres and ultimately used in preparation o f a composite was tested and is described. I t is thought that such fibres have the two potential advantages: ( 1) to enable manufacturing with pai1icle doped resins e.g. nanocomposites which add functionality to composites and (2) increased efficiency ofstructural composite manufacturing by increasing the level of automation. The structure of the thermoset fibres comprises of a sheath of thermoplastic and a core of uncured the1moset resin. Once manufactured, the fibres were wound with a reinforced fibre onto a plate, consolidated and cured. The resulting composite was examined and compared to other composites made with the same manufacturing method from commercially available materials. The results show that a laminate can be produced using these reactive bicomponent fibres. The resin system successfully impregnates the reinforcing carbon fibres and that the thermoplas- tic separates from the epoxy resin system during consolidation. In comparison to reference material, the bicomponentlaminate shows promising characteristics. However, the processes developed are currently on a lab-scale and consid- erable improvement of various bicomponent fibre properties, such as the strength, are required before the technology can be used on a larger scale

  • 18.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Swerea SICOMP AB, Box 271, SE-941 26 Piteå.
    Hagström, Bengt
    werea IVF AB.
    Långström, Runar
    Swerea SICOMP AB, Box 271, SE-941 26 Piteå.
    Fernberg, Patrik
    Swerea SICOMP AB, Box 271, SE-941 26 Piteå.
    Novel reactive bicomponent fibres: Material in composite manufacturing2012In: Journal of Nanostructured Polymers and Nanocomposites, ISSN 1790-4439, Vol. 8, no 1, p. 5-11Article in journal (Refereed)
    Abstract [en]

    The hypotheses that reactive uncured, thermoset bicomponent fibres can be prepared and mixed with reinforcing fibres and ultimately used in preparation of a composite was tested and is described. It is thought that such fibres have the two potential advantages: (1) to enable manufacturing with particle doped resins e.g. nanocomposites which add functionality to composites and (2) increased efficiency of structural composite manufacturing by increasing the level of automation. The structure of the thermoset fibres comprises of a sheath of thermoplastic and a core of uncured thermoset resin. Once manufactured, the fibres were wound with a reinforced fibre onto a plate, consolidated and cured. The resulting composite was examined and compared to other composites made with the same manufacturing method from commercially available materials. The results show that a laminate can be produced using these reactive bicomponent fibres. The resin system successfully impregnates the reinforcing carbon fibres and that the thermoplastic separates from the epoxy resin system during consolidation. In comparison to reference material, the bicomponent laminate shows promising characteristics. However, the processes developed are currently on a lab-scale and considerable improvement of various bicomponent fibre properties, such as the strength, are required before the technology can be used on a larger scale.

  • 19.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jonoobi, Mehdi
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Impregnation of cellulose nanofibre networks with a thermoplastic polymer2013Conference paper (Other academic)
    Abstract [en]

    The emphasis of this study have been to study if impregnation of cellulose nanofibre networks can be made using a thermoplastic polymer as a matrix and to estimate the reinforcing efficiency of the cellulose nanofibres in this composite. A nanofibre network with higher porosity that water-dried nanofibre network was prepared from a cellulose waste byproduct (sludge). This was impregnated using a diluted solution of cellulose acetate butyrate polymer to produce a 60 wt. % CNF/CAB composite. This composite was characterized using microscopy and mechanical testing. High porosity is seen in the SEM images of the acetone-dried fibre network and SEM and film transparency was used to qualitatively assess the impregnation of the network. A significant improvement in the visible light transmittance was observed for the nanocomposite film compared to the nanofibre network as a result of the impregnation. The reinforcing efficiency was calculated based on a model of the nanocomposite and compared to other nanocomposites in the literature. The efficiency factor takes into account the volume fraction and the stiffness of the matrix. This showed that this CNF/CAB combination is similar in efficiency to CNF/PLA nanocomposites and more efficient that nanocomposites using when using stiffer matrices. It was also more efficient CNF nanocomposites based on Chitosan, which has the same stiffness. It is still however not as efficient as traditional glass polymer composites due to the random orientation of the fibres nor nanocomposites with very soft matrices due to the dominating network effect of the CNF in such composites. In conclusion, CAB impregnated cellulose nanofibre networks are promising biocomposite materials that could be used in applications where transparency and good mechanical properties are of interest. The key elements in the impregnation process of the nanocomposites were the use of a porous networks and a low viscosity thermoplastic resin solution.

  • 20.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sounding Out Paper Pulp: Ultrasound Spectroscopy of Dilute Viscoelastic Fibre Suspensions Acoustics and Ultrasonics2006Conference paper (Other academic)
    Abstract [en]

    A model of attenuation of ultrasound in fibre suspensions is compared to a model of backscattering pressure from submersed cylinders subjected to a sound wave. This analysis is carried out in the region where the wavelength is of the same order as that of the diameter of the fibre. In addition we assume the cylinder scatterer to have no intrinsic attenuation and the longitudinal axis of the scatterer is assumed to be perpendicular to the direction of propagation of the incident wave. Peaks in the frequency response of both the backscattering pressure, expressed in the form of a form function, and the attenuation are shown to correspond. Similarities between the models are discussed. Since the peaks in the form function are due to resonance of the cylinder, we infer that the peaks in the attenuation are also due to resonance. The exact nature of the waves causing the resonance are still unclear however the first resonance peaks are related to the shear wave and hence the shear modulus of the material. The aim is to use the attenuation model for solving the inverse problem of calculating paper pulp material properties from attenuation measurements. The implications of these findings for paper pulp property estimation is that the supporting fluid could, if possible, be matched to density of that of pulp fibres and that the estimation of material properties should be improved by selecting a frequency range that in the region of the first resonance peaks.

  • 21.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Estimating material properties of solid and hollow fibers in suspension using ultrasonic attenuation2013In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 60, no 7, p. 1424-1434Article in journal (Refereed)
    Abstract [en]

    Estimates of the material properties of hollow fibers suspended in a fluid using ultrasound measurements and a simple, computationally efficient analytical model are made. The industrial application is to evaluate the properties of wood fibers in paper pulp. The necessity of using a layered cylindrical model (LCM) as opposed to a solid cylindrical model (SCM) for modeling ultrasound attenuation in a suspension of hollow fibers is evaluated. The two models are described and used to solve the inverse problem of estimating material properties from attenuation in suspensions of solid and hollow polyester fibers. The results show that the measured attenuation of hollow fibers differs from that of solid fibers. Elastic properties estimates using LCM with hollow-fiber suspension measurements are similar to those using SCM with solid-fiber suspension measurements and compare well to block polyester values for elastic moduli. However, using the SCM with the hollow-fiber suspension did not produce realistic estimations. In conclusion, the LCM gives reasonable estimations of hollow fiber properties and the SCM is not sufficiently complex to model hollow fibers. The results also indicate that the use of a distributed radius in the model is important in estimating material properties from fiber suspensions.

  • 22.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Moreno, Sergio
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vacuum infusion of cellulose nanofibre network composites: Influence of porosity on permeability and impregnation2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 95, p. 204-211Article in journal (Refereed)
    Abstract [en]

    Addressing issues around the processing of cellulose nanofibres (CNF) composites is important in establishing their use as sustainable, renewable polymer reinforcements. Here, CNF networks of different porosity were made with the aim of increasing their permeability and suitability for processing by vacuum infusion (VI). The CNF networks were infused with epoxy using two different strategies. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated. Calculated fill-times for CNF networks with 50% porosity were the shortest, but are only less than the gel-time of the epoxy if capillary effects are included. In experiments the CNF networks were clearly wetted. However low transparency indicated that impregnation was incomplete. The modulus and strength of the dry CNF networks increased rapidly with decreasing porosity, but their nanocomposites did not follow this trend, showing instead similar mechanical properties to each other. The results demonstrated that increasing the porosity of the CNF networks to ≈ 50% gives better impregnation resulting in a lower ultimate strength, a higher yield strength and no loss in modulus. Better use of the flow channels in the inherently layered CNF networks could potentially reduce void content in these nanocomposites and thus increase their mechanical properties.

  • 23.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Moreno, Sergio
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vacuum Infusion of Nanocellulose Networks of Different Porosity2015In: 20th International Conference on Composite Materials: Copenhagen, 19-24th July 2015, ICCM , 2015, article id 4109-1Conference paper (Refereed)
    Abstract [en]

    Cellulose nanofibres (CNF) have shown good potential as sustainable, biobased reinforcing materials in polymer composites. Addressing issues around the processing of these composites is an important part of establishing their use in different applications. Here, CNF networks of different porosity are made from nanofibrillated hardwood kraft pulp with the aim of increasing the impregnation of the CNF networks and to allow vacuum infusion to be used. Two different vacuum infusion strategies: in-plane and out of plane were used to infuse the CNF networks with a low viscosity epoxy. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated and compared to a micro-fibre based network. Using the out-of-plane permeability measurements and Darcy’s law, the fill-time was calculated and showed that the CNF network with 40% porosity had the lowest fill-time when an out-of-plane impregnation strategy is used. However this exceeded the gel-time of the epoxy system. In experiments, the resin reached the other side of the network but low transparency indicated that wetting was poor. The dry CNF preforms showed a very strong dependence on the porosity with both modulus and strength increasing rapidly at low porosity. Interestingly, the composite based on the 60% porosity network showed good wetting particularly with the in-plane infusion strategy, exhibiting a much more brittle fracture and a high yield strength. This shows that in CNF composites produced by VI, lowering the fibre volume content of the CNF composites gives better impregnation resulting in a lower ultimate strength but higher yield strength and no loss in modulus.

  • 24.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanofibril nanocomposites processing2013In: Production and Applications of Cellulose Nanomaterials, Peachtree Corners, GA: TAPPI Press, 2013, p. 271-274Chapter in book (Refereed)
    Abstract [en]

    Impregnation of a preformed network of nanofibrils leads to high fibre volume fraction nanocomposites and with this good mechanical properties have been achieved. However, comparing nanofibrils composite made with different volume fractions and different matrices is difficult. In order to do this, and in doing so gain insight into the most promising approaches, methods of measuring reinforcing efficiencies are being developed. The results show that for matrices with low stiffness the stiffness reinforcing efficiency is high. However with high fibre volume fraction and high stiffness, this network effect may lead to a lack of exploitation of the properties of the nanofibrils. Alignment of the nanofibrils is also a key in effective reinforcement. In addition, upscaling of the impregnation process requires a good understanding of permeability and adaptation of existing permeability models for cellulose nanofibrils networks as well as experiments on their permeability are ongoing.

  • 25.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Quantifying reinforcing efficiency of nanocellulose fibres2013In: Processing of fibre composites-challenges for maximum materials performance: Proceedings of 34th Risø International Symposium on Materials Science / [ed] Bo Madsen; Hans Lilholt; Y Kusano; S Fäster; B Ralph, Risö: Dept. of Wind Energy, Technical University of Denmark , 2013, p. 149-160Conference paper (Refereed)
    Abstract [en]

    Cellulose nanofibres are found in all plants and have the potential to provide a sustainable biobased material source. These nanofibres can be used for reinforcing polymers and thus as structural materials. Very promising results have been reported for different nanocomposites but to compete with existing materials, it is important to understand what progress has been made towards structural materials using nanocellulose. To do this the reinforcing efficiency of the stiffness and strength of nanocellulose in different nanocomposites has been calculated for a number of reported nanocellulose fibre based composites. For the stiffness this is done by back-calculating a reinforcing efficiency factor from a Halpin-Tsai model and laminate theory. For the strength efficiency, two models are used: a classic short fibre composite model and a network model. The results show that orientation is key to the stiffness efficiency, as shown by the high efficiency of aligned natural fibres. The stiffness efficiency is, as expected, high in soft matrices but in stiff matrices, the network effect of the nanofibres is possibility limiting their reinforcing potential. The strength efficiency results show that in all the nanocomposites evaluated the network model is closer to predicting strength than the short fibre composite model. The correlation between the network strength and the composite strength suggest that much of the stress transfer is from fibre to fibre and strong nanocomposites depend heavily on having a strong network. Also noted is that in composite processing a good impregnation of the nanofibers is also seen as an important factor in the efficiency of both strength and stiffness.

  • 26.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Reinforcing efficiency and the manufacture nanocellulose fibre based composites by vacuum infusion2015Conference paper (Other academic)
    Abstract [en]

    Nanocomposites based on cellulose have received a rapidly rising attention over the last 10 years however the method of manufacturing these composites on a scale larger than that in the lab remains challenging. Another challenge is that low fraction nanocomposites, whilst they can show excellent improvement in polymer properties, have difficultly to compete with traditional fibre reinforced composites [1,2]. A commonly used liquid composite moulding method for producing composites is vacuum infusion and the possibility of trading glass fibre for nanocellulose networks sheets in this type of manufacturing could results in a upscale method for producing high volume fraction cellulose nanocomposites. CNF networks are stiff and strong but have high fibre packing and thus difficult to impregnate. This paper evaluates the effectiveness of increasing the porosity to improve their processability by VI.

  • 27.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Reinforcing efficiency of nanocellulose in polymers2014In: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 85, p. 151-156, article id 6Article in journal (Refereed)
    Abstract [en]

    Nanocellulose extracted from renewable sources, is a promising reinforcement for many polymers and is a material where strong interfibre hydrogen bonds add effects not seen in microfiber composites. Presented is a tool for comparing different nanocellulose composites based on estimating the efficiency of nanocellulose reinforcement. A reinforcing efficiency factor is calculated from reported values of elastic modulus and strength from various nanocellulose composites using established micromechanical models. In addition, for the strength, a network model is derived based on fibre-fibre bond strength within nanocellulose networks. The strength results highlight the importance of the plastic deformation in the nanocellulose composites. Both modulus and strength efficiency show that the network strength and modulus has a greater effect than that of the individual constituents. In the best cases, nanocellulose reinforcement exceeds all model predictions.

  • 28.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Reinforcing Efficiency of Nanocelluloses in Polymer Nanocomposites2014In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
  • 29.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Westin, Mikael
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hydrogel state impregnation of cellulose fibre-phenol composites: effects of fibre size distribution2016In: ECCM 2016: Proceeding of the 17th European Conference on Composite Materials, European Conference on Composite Materials , 2016Conference paper (Refereed)
    Abstract [en]

    Whilst it has been well established that cellulose nanofibres (CNF) networks produce films that have high stiffness and strength, they are difficult to impregnate. Investigated in this study is whether by controlling the degree of nanofibrillation of cellulose, composites based on micro- and nano-size cellulose fibres can be made that are more easily manufactured and have better impregnation than solely cellulose nano-fibre based composites. To evaluate this, cellulose at different stages of ultrafine grinding, extracted at time intervals of 30, 60 and 290 mins, were used to make composites. To achieve good impregnation a novel strategy was used based on impregnation with phenol resin whilst the fibrillated cellulose is in a hydrogel state. The composites were subsequently dried and consolidated by hot press. The current results show that this method of impregnation is successful and the phenol matrix greatly improves the properties of the cellulose with a low degree of fibrillation. In general, as the degree of fibrillation and the proportion of nanofibres increases, the mechanical properties of the networks and their composites increase. The addition of the matrix appears to restrict the deformation of CNF network, increasing the modulus and yield strength but decreasing the ultimate strength. The method also appears to restrict the consolidation and voids remain in the composite, which reduces the modulus when compared to theoretical maximum values for this material. More work on the consolidation process is necessary to achieve the full potential of these composites.

  • 30.
    Alemandar, Ayse
    et al.
    University of Toronto.
    Sain, Mohini
    University of Toronto.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    The effect of decreased fiber size in wheat straw / polyvinyl alchol composites2009In: Journal of Biobased Materials and Bioenergy, ISSN 1556-6560, E-ISSN 1556-6579, Vol. 3, no 1, p. 75-80Article in journal (Refereed)
    Abstract [en]

    The reinforcing potential of micro and nano-size fibers from wheat straw in polyvinyl alcohol (PVA) was studied. The microfibers were obtained by alkali treatment and disintegration process of wheat straw while nanofibers were obtained after applying further mechanical treatment of this alkali treated wheat straw. The results showed that the alkali treatment increased the α-cellulose content of the fibers from 38% to 73% due to hydrolysis of the hemicelluloses and lignin from the straw walls. The morphology and thermal properties of the micro and nano-size fibers were determined to show their potential as reinforcements. The transmission electron microscopy study showed that the size of the wheat straw fibers was decreased from micro to nano-size by the defibrillation process. Thermogravimetric analysis demonstrated the alkali treatment dramatically increased the thermal properties of the wheat straw fibers. The morphologies and thermal properties of the prepared composites were investigated by scanning electron microscopy and thermogravimetric analysis. The thermal stability of the nanofiber-reinforced composites increased with respect to the neat PVA. The mechanical properties of the composites increased significantly with the addition of microfibers and further increment was obtained with nanofibers. The tensile modulus increased from 2.1 GPa of pure PVA to 3 GPa with the addition of micro sized fibers and further to 3.8 GPa with the decreased fiber size to nano scale. The composites strength showed similar trend.

  • 31.
    Alemdar, Ayse
    et al.
    University of Toronto.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sain, Mohini
    University of Toronto.
    Reinforcement capability of wheat straw fibers from micro to nano size2007In: 9th International Conference on Wood & Biofiber Plastic Composites: held in Madison, Wisconsin, May 21 -23, 2007, Madison, Wis: Forest Products Society, 2007Conference paper (Refereed)
    Abstract [en]

    The goal of this study was to explore the reinforcement capability of micro and nano-size fibers from wheat straw. Microfibers were obtained by alkali treatment and disintegration processes of the wheat straw while nanofibers were obtained after applying further mechanical treatment of this alkali treated wheat straw. The morphology and thermal properties of both fiber types were determined to show their suitability as reinforcements. TEM images showed that the diameters of the wheat straw fibers were decreased from micro to nano-size by the defibrillation process. Thermogravimetric analysis showed the alkali treatment dramatically increased the thermal properties of the wheat straw fibers. The composites were produced using, respectively, the microfibers and nanofibers as reinforcement, with both polyvinyl alcohol (PVA) and cellulose acetate butyrate (CAB) as the matrix. The morphology and thermal properties of the composites were investigated by scanning electron microscopy and thermogravimetric analysis. The mechanical properties of the composites were compared with those of neat polymer matrix and found to be considerably improved.

  • 32.
    Alinejad, M.
    et al.
    Department of Forestry, Michigan State University, East Lansing, United States.
    Henry, C.
    Department of Forestry, Michigan State University, East Lansing, United States.
    Nikafshar, S.
    Department of Forestry, Michigan State University, East Lansing, United States.
    Gondaliya, A.
    Chemical Engineering and Materials Science, Michigan State University, East Lansing, United States.
    Bagheri, B.
    Chemical Engineering and Materials Science, Michigan State University, East Lansing, United States.
    Chen, N.
    Eastern Regional Research Center, USDA-ARS, Wyndmoor, United States.
    Singh, S.K.
    Chemical and Biological Engineering, Montana State University, Bozeman, United States.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Nejad, M.
    Department of Forestry, Michigan State University, East Lansing, United States. Chemical Engineering and Materials Science, Michigan State University, East Lansing, United States..
    Lignin-based polyurethanes: Opportunities for bio-based foams, elastomers, coatings and adhesives2019In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 7, article id 1202Article in journal (Refereed)
    Abstract [en]

    Polyurethane chemistry can yield diverse sets of polymeric materials exhibiting a widerange of properties for various applications and market segments. Utilizing lignin as a polyol presentsan opportunity to incorporate a currently underutilized renewable aromatic polymer into theseproducts. In this work, we will review the current state of technology for utilizing lignin as a polyolreplacement in different polyurethane products. This will include a discussion of lignin structure,diversity, and modification during chemical pulping and cellulosic biofuels processes, approachesfor lignin extraction, recovery, fractionation, and modification/functionalization. We will discussthe potential of incorporation of lignins into polyurethane products that include rigid and flexiblefoams, adhesives, coatings, and elastomers. Finally, we will discuss challenges in incorporating ligninin polyurethane formulations, potential solutions and approaches that have been taken to resolvethose issues.

  • 33.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Sepúlveda-Villarroel, Victor
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Perez-Peña, Natalia
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Leandro-Zuñiga, Laura
    Instituto Costarricense de la Madera, San Pedro, San José.
    Salvo-Sepúlveda, Linette
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Salinas-Lira, Carlos
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Cloutier, Alain
    Society of Wood Science & Technology Member, Centre de Recherche sur le Bois, Université Laval, Québec.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Collapse of Eucalyptus nitens Wood after Drying Depending on the Radial Location Within the Stem2014In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, no 14, p. 1699-1705Article in journal (Refereed)
    Abstract [en]

    Collapse is almost certain to occur in the industrial drying of Eucalyptus nitens, and as such this prevents the lumber manufacturing industry in Chile from producing commercial solid wood products from this species. This problem is still unsolved, and different studies to reduce collapse are currently underway. In this exploratory study, shrinkage and collapse after drying of Eucalyptus nitens was measured for boards cut from different radial locations within the stem (core, transition and outer wood from pith to bark) and having different annual ring orientation (flat-sawn and quarter-sawn). Even though exploratory, the results appear to confirm that pieces that were cut from the center of the trees were less susceptible to collapse than the pieces cut from the transition zone between the center and the periphery. On average, collapse in transition wood was approximately 50% higher than the collapse observed in wood cut from the central zone of the trees.

  • 34.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    Ulloa, J.
    Aserraderos Arauco S.A., Arauco.
    Elustondo, Diego
    FPInnovations—Forintek Division, Vancouver BC.
    Salinas, Carlos T S
    Department of Mechanical Engineering, Faculty of Engineering, University of Bío-Bío, Concepción, Mechanical Engineering Department, University of Bío-Bío, Concepción, Department of Mechanical Engineering, University of Bío-Bío, Concepción.
    Rebolledo, Pamela
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Fuentes, C.
    Aserraderos Arauco S.A., Arauco.
    Energy consumption in industrial drying of radiata pine2011In: Proceedings of the 7th Asia-Pacific Drying Conference: Tianjin, China, September 18-20 2011, 2011Conference paper (Refereed)
  • 35. Anasontzis, George
    et al.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Challenges in ethanol production with Fusarium oxysporum through consolidated bioprocessing2014In: Bioengineered, ISSN 2165-5979, E-ISSN 2165-5987, Vol. 5, no 6, p. 393-395Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Fusarium oxysporum has been reported as being able to both produce the enzymes necessary to degrade lignocellulosic biomass to sugars and also ferment the monosaccharides to ethanol under anaerobic or microaerobic conditions. However, in order to become an economically feasible alternative to other ethanol-producing microorganisms, a better understanding of its physiology, metabolic pathways, and bottlenecks is required, together with an improvement in its efficiency and robustness. In this report, we describe the challenges for the future and give additional justification for our recent publication.

  • 36.
    Anasontzis, George E.
    et al.
    National and Kapodistrian University of Athens, Chalmers University of Technology, Department of Chemical and Biological Engineering, Microbial Biotechnology Unit, Sector of Botany, Department of Biology, National and Kapodistrian University of Athens, Zografou.
    Kourtoglou, Elisavet
    National Technical University of Athens, BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Villas-Boâs, Silas G
    Centre for Microbial Innovation, School of Biological Sciences, The University of Auckland, Technical University of Denmark.
    Hatzinikolaou, Dimitris G.
    Department of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Metabolic Engineering of Fusarium oxysporum to Improve Its Ethanol-Producing Capability2016In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, article id 632Article in journal (Refereed)
    Abstract [en]

    Fusarium oxysporum is one of the few filamentous fungi capable of fermenting ethanol directly from plant cell wall biomass. It has the enzymatic toolbox necessary to break down biomass to its monosaccharides and, under anaerobic and microaerobic conditions, ferments them to ethanol. Although these traits could enable its use in consolidated processes and thus bypass some of the bottlenecks encountered in ethanol production from lignocellulosic material when Saccharomyces cerevisiae is used-namely its inability to degrade lignocellulose and to consume pentoses-two major disadvantages of F. oxysporum compared to the yeast-its low growth rate and low ethanol productivity-hinder the further development of this process. We had previously identified phosphoglucomutase and transaldolase, two major enzymes of glucose catabolism and the pentose phosphate pathway, as possible bottlenecks in the metabolism of the fungus and we had reported the effect of their constitutive production on the growth characteristics of the fungus. In this study, we investigated the effect of their constitutive production on ethanol productivity under anaerobic conditions. We report an increase in ethanol yield and a concomitant decrease in acetic acid production. Metabolomics analysis revealed that the genetic modifications applied did not simply accelerate the metabolic rate of the microorganism; they also affected the relative concentrations of the various metabolites suggesting an increased channeling toward the chorismate pathway, an activation of the γ-aminobutyric acid shunt, and an excess in NADPH regeneration

  • 37.
    Anasontzis, George
    et al.
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Kourtoglou, Elisavet
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Mamma, Diomi
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Villas-Boâs, Silas G
    Centre for Microbial Innovation, School of Biological Sciences, The University of Auckland.
    Hatzinikolaou, Dimitris
    Microbial Biotechnology Unit, Sector of Botany, Department of Biology, National and Kapodistrian University of Athens.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Constitutive homologous expression of phosphoglucomutase and transaldolase increases the metabolic flux of Fusarium oxysporum2014In: Microbial Cell Factories, ISSN 1475-2859, E-ISSN 1475-2859, Vol. 13, article id 43Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Fusarium oxysporum is among the few filamentous fungi that have been reported of being able to directly ferment biomass to ethanol in a consolidated bioprocess. Understanding its metabolic pathways and their limitations can provide some insights on the genetic modifications required to enhance its growth and subsequent fermentation capability. In this study, we investigated the hypothesis reported previously that phosphoglucomutase and transaldolase are metabolic bottlenecks in the glycolysis and pentose phosphate pathway of the F. oxysporum metabolism.RESULTS: Both enzymes were homologously overexpressed in F. oxysporum F3 using the gpdA promoter of Aspergillus nidulans for constitutive expression. Transformants were screened for their phosphoglucomutase and transaldolase genes expression levels with northern blot. The selected transformant exhibited high mRNA levels for both genes, as well as higher specific activities of the corresponding enzymes, compared to the wild type. It also displayed more than 20 and 15% higher specific growth rate upon aerobic growth on glucose and xylose, respectively, as carbon sources and 30% higher xylose to biomass yield. The determination of the relative intracellular amino and non-amino organic acid concentrations at the end of growth revealed higher abundance of most determined metabolites between 1.5- and 3-times in the recombinant strain compared to the wild type. Lower abundance of the determined metabolites of the Krebs cycle and an 68-fold more glutamate were observed at the end of the cultivation, when xylose was used as carbon source.CONCLUSIONS: Homologous overexpression of phosphoglucomutase and transaldolase in F. oxysporum was shown to enhance the growth characteristics of the strain in both xylose and glucose in aerobic conditions. The intracellular metabolites profile indicated how the changes in the metabolome could have resulted in the observed growth characteristics.

  • 38.
    Andersson, Christian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Biobased production of succinic acid by Escherichia coli fermentation2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The prospects of peak oil, climate change and the dependency of fossil carbon have urged research and development of production methods for the manufacture of fuels and chemicals from renewable resources (biomass). The present thesis illustrates different aspects of biobased succinic acid production by a metabolically engineered E. coli strain. The main areas of the thesis are sugar utilisation and feedstock flexibility, and fermentation inhibition, both due to toxic compound derived from the raw material and the fermentation products themselves.The first part of this thesis aimed to investigate the fermentation characteristics of AFP184 in a medium consisting of corn steep liquor, inorganic salts and different sugar sources without supplementation with high-cost nutrients such as yeast extract and peptone. The effects of different sugars, sucrose, glucose, fructose, xylose, equal mixtures of glucose-fructose and glucose-xylose, on succinic acid production kinetics and yields in an industrially relevant medium were investigated. AFP184 was able to utilise all sugars and sugar combinations except sucrose for biomass generation and succinate production. Using glucose resulted in the highest yield, 0.83 (g succinic acid per g sugar consumed anaerobically). Using a high initial sugar concentration resulted in volumetric productivities of almost 3 g L-1 h-1, which is above estimated values for economically feasible production. However, succinic acid production ceased at final concentrations greater than 40 g L-1. To further increase succinic acid concentrations, fermentations using NH4OH, NaOH, KOH, K2CO3, and Na2CO3 as neutralising agents were performed and compared. It was shown that substantial improvements could be made by using alkali bases to neutralise the fermentations. The highest concentrations and productivities were achieved when Na2CO3 was used, 77 g L-1 and 3 g L-1 h-1 respectively. A gradual decrease in succinate productivity was observed during the fermentations, which was shown to be due to succinate accumulation in the broth and not as a result of the addition of neutralising agent or the subsequent increase in osmolarity.To maintain high succinate productivity by keeping a low extracellular succinic acid concentration fermentations were interrupted and cells recovered and resuspended in fresh media. By removing the succinate it was possible to maintain high succinic acid productivity for a prolonged time. Cells subjected to high concentrations of succinate were also able to regain high productivity once transferred into a succinate-free medium.In the last part of the thesis succinic acid production from softwood dilute acid hydrolysates was demonstrated. This study involved establishing the degree of detoxification necessary for growth and fermentation using industrial hydrolysates. Detoxification by treatment with lime and/or activated carbon was investigated and the results show that it was possible to produce succinate from softwood hydrolysates in yields comparable to those for synthetic sugars.The work done in this thesis increases the understanding of succinic acid production with AFP184, illustrate its limitations, and suggests improvements in the current technology with the long term aim of increasing the economical feasibility of biochemical succinic acid production.

  • 39. Andersson, Christian
    Succinic acid production using metabolically engineered Escherichia coli2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The prospects of peak oil, climate change and the dependency of fossil carbon have urged research and development of production methods for the manufacture of fuels and chemicals from renewable resources (biomass). To date, the primary emphasis has been placed on the replacement of oil for transportation fuels. A highly significant subset of petroleum usage is the production of chemicals, which represents 10-15% of the petroleum usage. White biotechnology, also called industrial biotechnology, is a fast evolving technology with a large potential to have a substantial impact on the industrial production of fuels and chemicals from biomass. This work addresses the issue of chemical production by investigating the production of bio-based succinic acid, which can be used in a wide range of applications to replace petroleum based chemicals. Succinic acid can be produced by fermentation of sugar by a number of organisms; one is Escherichia coli (E. coli). It is known that E. coli under anaerobic conditions produces a mixture of organic acids. In order to obtain a cost-effective production it is necessary to metabolically engineer the organism to produce succinic acid in greater yield than the other acids. In the current work, E. coli mutant AFP184 was used. AFP184 originates from a near wild type strain, the C600 (ATCC 23724), which can ferment both five and six carbon sugars and has mutations in the glucose specific phosphotransferase system (ptsG), the pyruvate formate lyase system (pfl) and in the fermentative lactate dehydrogenase system (ldh). The previous studies using different organisms have all used cultivation mediums supplemented to some degree with different nutrients like biotin, thiamine and yeast extract. In order to apply the technology to large scale, production must be cost-effective and it is important to minimise the use of additional supplements. The first part of this work aimed to investigate the fermentation characteristics of AFP184 in a medium consisting of corn steep liquor, inorganic salts and different sugar sources without supplementation of other additional nutrients. It addresses questions regarding the effect of different sugars on succinic acid kinetics and yields in an industrially relevant medium. In order to gain a sustainable production of succinic acid from biomass feedstocks (sugar from biomass) it is important to investigate how well the organism can utilise different sugars in the biomass. The sugars studied were sucrose, glucose, fructose, xylose and equal mixtures of glucose-fructose and glucose-xylose at a total initial sugar concentration of 100 g L-1. AFP184 was able to utilise all sugars and sugar combinations except sucrose for biomass generation and succinate production. Using glucose resulted in the highest yield, 0.83 (g succinic acid per g sugar consumed anaerobically). Fructose resulted in a yield of 0.66 and xylose of 0.5. Using a high initial sugar concentration made it possible to obtain volumetric productivities of almost 3 g L-1h-1, which is above estimated values for feasible economic production. Succinic acid production ceased at final concentrations greater than 40 g L-1. In order to further increase succinic acid concentrations, this inhibitory effect was studied in the second part of the present work. The inhibitory effects can be two-fold including pH-based inhibition and an anion specific effect on metabolism. It has been reported that high concentrations of ammonia inhibit E. coli growth and damage cell membranes. In order to limit toxic and inhibitory effects different neutralising agents were tested. First the use of NH4OH was optimised with respect to fermentation pH and it was found that the best results were obtained at pH 6.5-6.7. Optimal pH was then used with NaOH, KOH, and Na2CO3 as neutralising agents and it was shown that NaOH, KOH, and Na2CO3 neutralised fermentations could reach succinic acid concentrations of 69 and 61 and 78 g L-1 respectively without any significant decrease in succinic acid productivity. It was observed that cells lost viability during the cause anaerobic phase. It resulted in decreasing succinic acid productivities. It is believed that the viability decrease is a combined effect of organic acids concentration and the osmolarity of the medium. The work done in this thesis is aimed towards increasing the economical feasibility of a biochemical succinic acid production.

  • 40. Andersson, Christian
    et al.
    Helmerius, Jonas
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Effects of neutralising agent, organic acids, and osmolarity on succinic acid production by Escherichia coli AFP1842008Conference paper (Other academic)
    Abstract [en]

    Using a low-cost medium Escherichia coli AFP184 has previously been reported to produce succinic acid with volumetric productivities close to 3 g L-1 h-1. At a total organic acid concentration of 30 g L-1 the productivity decreased drastically resulting in final succinate concentrations of 40 g L-1. The economical viability of biochemical succinic acid production would benefit from higher final succinic acid concentrations and volumetric productivities maintained at >2.5 g L-1 h-1 for an extended period of time. In the present work the effects of osmolarity and neutralising agent (NH4OH, KOH, NaOH, K2CO3, and Na2CO3) on succinic acid production by AFP184 were investigated. Highest concentration of succinic acid was obtained with Na2CO3, 75 g L-1. It was also found that the osmolarity resulting from succinate production and subsequent base addition, only marginally affected the productivity per viable cell. Organic acid inhibition due to the produced succinic acid on the other hand significantly reduced succinic acid productivity per viable cell. When using NH4OH productivity completely ceased at approximately 40 g L-1. Volumetric productivities remained at 2.5 g L-1 h-1 for 5 to 10 hours longer when using K- or Na-bases than when using NH4OH. However, loss of cell viability occurred, and together with the acid inhibition decreased the volumetric productivities. In this study it was demonstrated that by altering the neutralising agent it was possible to increase the period of high volumetric productivity in the anaerobic phase and improve the final succinic acid concentration by almost 100 %

  • 41. Andersson, Christian
    et al.
    Helmerius, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hodge, David
    Berglund, Kris
    Rova, Ulrika
    Inhibition of succinic acid production in metabolically engineered Escherichia Coli by neutralizing agent, organic acids, and osmolarity2009In: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 25, no 1, p. 116-123Article in journal (Refereed)
    Abstract [en]

    The economical viability of biochemical succinic acid production is a result of many processing parameters including final succinic acid concentration, recovery of succinate, and the volumetric productivity. Maintaining volumetric productivities >2.5 g L-1 h(-1) is important if production of succinic acid from. renewable resources should be competitive. In this work, the effects of organic acids, osmolarity, and neutralizing agent (NH4OH, KOH, NaOH, K2CO3, and Na2CO3) on the fermentative succinic acid production by Escherichia coli AFP184 were investigated. The highest concentration of succinic acid, 77 g L-1. was obtained with Na2O3. In general, irrespective of the base used, succinic acid productivity per viable cell was significantly reduced as the concentration of the produced acid increased. Increased osmolarity resulting from base addition during succinate production only marginally affected the productivity per viable cell. Addition of the osmoprotectant glycine betaine to cultures resulted in an increased aerobic growth rate and anaerobic glucose consumption rate, but decreased succinic acid yield. When using NH4OH productivity completely ceased at a succinic acid concentration of similar to 40 g L-1. Volumetric productivities remained at 2.5 g L-1 h(-1) for tip to 10 h longer when K- or Na-bases where used instead of NH4OH. The decrease in cellular succinic acid productivity observed during the anaerobic phase was found to be due to increased organic acid concentrations rather than medium osmolarity.

  • 42. Andersson, Christian
    et al.
    Hodge, David
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rova, Ulrika
    Effect of different carbon sources on the production of succinic acid using metabolically engineered Escherichia coli2007In: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 23, no 2, p. 381-388Article in journal (Refereed)
    Abstract [en]

    Succinic acid (SA) is an important platform molecule in the synthesis of a number of commodity and specialty chemicals. In the present work, dual-phase batch fermentations with the E. coli strain AFP184 were performed using a medium suited for large-scale industrial production of SA. The ability of the strain to ferment different sugars was investigated. The sugars studied were sucrose, glucose, fructose, xylose, and equal mixtures of glucose and fructose and glucose and xylose at a total initial sugar concentration of 100 g L-1. AFP184 was able to utilize all sugars and sugar combinations except sucrose for biomass generation and succinate production. For sucrose as a substrate no succinic acid was produced and none of the sucrose was metabolized. The succinic acid yield from glucose (0.83 g succinic acid per gram glucose consumed anaerobically) was higher than the yield from fructose (0.66 g g-1). When using xylose as a carbon source, a yield of 0.50 g g-1 was obtained. In the mixed-sugar fermentations no catabolite repression was detected. Mixtures of glucose and xylose resulted in higher yields (0.60 g g-1) than use of xylose alone. Fermenting glucose mixed with fructose gave a lower yield (0.58 g g-1) than fructose used as the sole carbon source. The reason is an increased pyruvate production. The pyruvate concentration decreased later in the fermentation. Final succinic acid concentrations were in the range of 25-40 g L-1. Acetic and pyruvic acid were the only other products detected and accumulated to concentrations of 2.7-6.7 and 0-2.7 g L-1. Production of succinic acid decreased when organic acid concentrations reached approximately 30 g L-1. This study demonstrates that E. coli strain AFP184 is able to produce succinic acid in a low cost medium from a variety of sugars with only small amounts of byproducts formed.

  • 43. Andersson, Christian
    et al.
    Lundberg, Angela
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Distribution of snow cover accumulation: airborne ground penetrating radar surveys2002In: Proceedings of the XXII Nordic Hydrological Conference / [ed] Å. Killingtveit, 2002, p. 517-526Conference paper (Refereed)
  • 44. Andersson, Christian
    et al.
    Petrova, Ekaterina
    Luleå tekniska universitet.
    Berglund, Kris
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Maintaining high anaerobic succinic acid productivity by product removal2010In: Bioprocess and biosystems engineering (Print), ISSN 1615-7591, E-ISSN 1615-7605, Vol. 33, no 6, p. 711-718Article in journal (Refereed)
    Abstract [en]

    During dual-phase fermentations using Escherichia coli engineered for succinic acid production, the productivity and viable cell concentration decrease as the concentration of succinic acid increases. The effects of succinic acid on the fermentation kinetics, yield, and cell viability were investigated by resuspending cells in fresh media after selected fermentation times. The cellular succinic acid productivity could be restored, but cell viability continuously decreased throughout the fermentations by up to 80% and subsequently the volumetric productivity was reduced. Omitting complex nutrients in the resuspension media had no significant effect on cellular succinate productivity and yield, although the viable cell concentration and thus the volumetric productivity was reduced by approximately 20%. By resuspending the cells, the amount of succinate produced during a 100-h fermentation was increased by more than 60%. The results demonstrate that by product removal succinic acid productivity can be maintained at high levels for extended periods of time.

  • 45.
    Andersson, Christian
    et al.
    Luleå University of Technology.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Process for producing succinic acid from sucrosePatent (Other (popular science, discussion, etc.))
    Abstract [en]

    A process for hydrolyzing sucrose to glucose and fructose using succinic acid is described. The hydrolysate can be used to produce purified glucose and/or fructose or can be used as a carbon source for fermentations to produce various chemicals including succinic acid.

  • 46.
    Andersson, Jan-Erik
    et al.
    SP Sveriges Tekniska Forskningsinstitut, SP Trä.
    Nordman, Roger
    SP Sveriges Tekniska Forskningsinstitut, SP Energiteknik.
    Vikberg, Tommy
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Energy mapping in the sawmill industry with focus on drying kilns2013Conference paper (Refereed)
    Abstract [en]

    The forest industry stands for approximately 11 % of Sweden’s total export. However, the forest industry is energy intensive. In 2008, sawmill industry alone consumed almost 8,7 TWh of energy, corresponding to 5 % of the Swedish industries total energy consumption. Out of their total consumption, 2200 GWh was electric power, 194 GWh heating oil , 4229 GWh bio-fuel, 574 GWh district heating, and other fuels such as diesel 1503 GWh [1].The project ”EESI- Energy Efficiency in the Sawmill Industry” was started in the spring of 2010 with the aim of demonstrating the possibilities to reduce the energy consumption in the sawmill industry with 20 % by 2020. 16 sawmill corporations and 14 equipment suppliers has joined the project which is carried out in two phases of which the first phase was carried out during 2010 and 2011. EESI has now reached half time and the first energy-saving implementations have been completed at the participating sawmills.This paper presents the energy-mapping, measurements and modelling performed by the participating sawmills during the first phase of the project [2, 3]. The average energy consumption per sawn cubic metre of boards varied between approximately 300 to 500 kWh/m3. Out of this, the electricity consumption was on average 85 kWh/m3, bio-fuel 290 kWh/m3 and diesel 1.8 l/m3.However, the main concern from sawmills regarding energy consumption was the wood drying process. The striking results from the preliminary measurements were the large variation in energy consumption even with similar drying kilns. This was especially apparent for the heat consumption in kiln dryers which could vary as much as 50 % for the same dimension of spruce planks.The results from the first phase of the project resulted in a large number of actions in order to reduce the energy consumption which are now being implemented or have already been completed. Examples of those actions are: simplified management system adapted to sawmills, weighing of packages for more accurate wood drying, reduced speed or intermittent operation of the air circulating fans in batch kilns and moisture content measurements of bio-fuel.References[1] Statistiska centralbyrån (SCB), 2013, Industrins årliga energianvändning 2011, Slutliga uppgifter, EN23SM1301, ISSN 1654-367X. (In Swedish). [2] Andersson, J-E., Lycken, A., Nordman, R., Olsson, M., Räftegård, O., and Wamming, T. State of the art – Energianvändning i den svenska sågverksindustrin. SP Rapport 2011:42, ISBN 978-91-86622-72-5. (In Swedish).[3] Andersson, J-E., Räftegård, O., Lycken, A., Olsson, M., Wamming, T., and Nordman, R. Sammanställning av energimätningar från EESI fas 1. SP Rapport 2011:41, ISBN 978-91-86622-71-8. (In Swedish).

  • 47.
    Andraous, Johnny I.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Claus, Michael J
    Department of Agricultural Engineering, Michigan State University.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lindemann, Deirdre J.
    Department of Chemistry, Michigan State University.
    Effect of liquefaction enzymes on methanol concentration of distilled fruit spirits2004In: American Journal of Enology and Viticulture, ISSN 0002-9254, E-ISSN 1943-7749, Vol. 55, no 2, p. 199-201Article in journal (Refereed)
    Abstract [en]

    Liquefaction enzymes are often used during fermentation of fruit mashes to improve the yield of ethanol and the ability to pump the mash. The liquefaction enzymes hydrolyze pectin, but in addition to the desired pectin hydrolysis activity, the enzymes also have pectinesterase activity which hydrolyzes the methyl ester in pectin resulting in methanol formation. Fermentations of various apple varieties and Bartlett pears were conducted using liquefaction enzymes. The resulting distilled products contained concentrations of methanol above the legal limit of 280 mg/100 mL of 40% ethanol, with the observed methanol concentrations in a range between 320 and 656 mg/100 mL of 40% ethanol. In contrast to the undesired increase in methanol concentration, the enzymes provide only a marginal increase in ethanol yield. The results indicate that liquefaction enzymes should be used with caution for pomace fruit and that methanol monitoring should be implemented if these enzymes are used for commercial products.

  • 48.
    Antonopoulou, Io
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Development of biocatalytic processes for selective antioxidant production2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Feruloyl esterases (FAEs, EC 3.1.1.73) represent a subclass of carboxylic acid esterases that under normal conditions catalyze the hydrolysis of the ester bond between hydroxycinnamic acids (ferulic acid, sinapic acid, caffeic acid, p-coumaric acid) and sugar residues in plant cell walls. Based on their specificity towards monoferulates and diferulates, substitutions on the phenolic ring and on their amino acid sequence identity, they have been classified into four types (A-D) while phylogenetic analysis has resulted in classification into thirteen subfamilies (SF1-13). Under low water content, these enzymes are able to catalyze the esterification of hydroxycinnamic acids or the transesterification of their esters (donor) with alcohols or sugars (acceptor) resulting in compounds with modified lipophilicity, having a great potential for use in the tailor-made modification of natural antioxidants for cosmetic, cosmeceutical and pharmaceutical industries. The work described in this thesis focused on the selection,characterization and application of FAEs for the synthesis of bioactive esters with antioxidant activity in non-conventional media. The basis of the current classification systems was investigated in relation with the enzymes’ synthetic and hydrolytic abilities while the developed processes were evaluated for their efficiency and sustainability.

    Paper I was dedicated to the screening and evaluation of the synthetic abilities of 28 fungal FAEs using acceptors of different lipophilicity at fixed conditions in detergentless microemulsions. It was revealed that FAEs classified in phylogenetic subfamilies related to acetyl xylan esterases (SF5 and 6) showed increased transesterification rates and selectivity. In general, FAEs showed preference on more hydrophilic alcohol acceptors and in descending order to glycerol > 1-butanol > prenol. Homology modeling and small molecule docking simulations were employed as tools for the identification of a potential relationship between the predicted surface and active site properties of selected FAEs and the transesterification selectivity.

    Papers II- IV focused on the characterization of eight promising FAEs and the optimization of reaction conditions for the synthesis of two bioactive esters (prenyl ferulate and L-arabinose ferulate) in detergentless microemulsions. The effect of the medium composition, the donor and acceptor concentration, the enzyme load, the pH, the temperature and the agitation on the transesterification yield and selectivity were investigated. It was observed that the acceptor concentration and enzyme load were crucial parameters for selectivity. Fae125 (Type A, SF5) iiexhibited highest prenyl ferulate yield (81.1%) and selectivity (4.685) converting 98.5% of VFA to products after optimization at 60 mM VFA, 1.5 M prenol, 0.04 mg FAE mL-1, 40oC, 24 h, 53.4:43.4:3.2 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0. On the other hand, FaeA1 (Type A, SF5) showed highest L-arabinose ferulate yield (52.2 %) and selectivity (1.120) at 80 mM VFA, 55 mM L-arabinose, 0.02 mg FAE mL-1, 50oC, 8 h, 19.8: 74.7: 5.5 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0.

    In paper V, the effect of reaction media on the enzyme stability and transesterification yield and selectivity was studied in different solvents for the synthesis of two bioactive esters: prenyl ferulate and L-arabinose ferulate. The best performing enzyme (Fae125) was used in the optimization of reaction conditions in the best solvent (n-hexane) via response surface methodology. Both bioconversions were best described by a two-factor interaction model while optimal conditions were determined as the ones resulting in highest yield and selectivity.Highest prenyl ferulate yield (87.5%) and selectivity (7.616) were observed at 18.56 mM prenol mM-1VFA, 0.04 mg FAE mL-1, 24.5 oC, 24.5 h, 91.8: 8.2 v/v n-hexane: 100 mM sodium acetate pH 4.7. Highest L-arabinose ferulate yield (56.2%) and selectivity (1.284) were observed at 2.96 mM L-arabinose mM-1VFA, 0.02 mg FAE mL-1, 38.9 oC, 12 h, 90.5: 5.0: 4.5 v/v/v n-hexane: dimethyl sulfoxide: 100 mM sodium acetate pH 4.7. The enzyme could be reused for six consecutive reaction cycles maintaining 66.6% of its initial synthetic activity. The developed bioconversions showed exceptional biocatalyst productivities (> 300 g product g-1FAE) and the waste production was within the range of pharmaceutical processes.

    Paper VI focused on the investigation of the basis of the type A classification of a well-studied FAE from Aspergillus niger(AnFaeA) by comparing its activity towards methyl and arabinose hydroxycinnamic acid esters. For this purpose, L-arabinose ferulateand caffeate were synthesized enzymatically. kcat/Kmratios revealed that AnFaeA hydrolyzed arabinose ferulate 1600 times and arabinose caffeate 6.5 times more efficiently than methyl esters. This study demonstrated that short alkyl chain hydroxycinnamate esters which are used nowadays for FAE classification can lead to activity misclassification, while L-arabinose esters could potentially substitute synthetic esters in classification describing more adequately the enzyme specificitiesin the natural environment.

  • 49.
    Antonopoulou, Io
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dilokpimol, Adiphol
    Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University.
    Iancu, Laura
    Dupont Industrial Biosciences.
    Mäkelä, Miia R.
    Department of Microbiology, University of Helsink.
    Varriale, Simona
    Department of Chemical Sciences, University of Naples “Federico II”.
    Cerullo, Gabriella
    Department of Chemical Sciences, University of Naples “Federico II”.
    Hüttner, Silvia
    Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology.
    Uthoff, Stefan
    Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster.
    Jütten, Peter
    Taros Chemicals GmbH & Co KG.
    Piechot, Alexander
    Taros Chemicals GmbH & Co KG.
    Steinbüchel, Alexander
    nstitut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster.
    Olsson, Lisbeth
    Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology.
    Faraco, Vincenza
    Department of Chemical Sciences, University of Naples “Federico II”.
    Hildén, Kristiina
    Department of Microbiology, University of Helsinki.
    de Vries, Ronald
    Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    The Synthetic Potential of Fungal Feruloyl Esterases: A Correlation with Current Classification Systems and Predicted Structural Properties2018In: Catalysts, ISSN 2073-4344, Vol. 8, no 6, article id 242Article in journal (Refereed)
    Abstract [en]

    Twenty-eight fungal feruloyl esterases (FAEs) were evaluated for their synthetic abilities in a ternary system of n-hexane: t-butanol: 100 mM MOPS-NaOH pH 6.0 forming detergentless microemulsions. Five main derivatives were synthesized, namely prenyl ferulate, prenyl caffeate, butyl ferulate, glyceryl ferulate, and l-arabinose ferulate, offering, in general, higher yields when more hydrophilic alcohol substitutions were used. Acetyl xylan esterase-related FAEs belonging to phylogenetic subfamilies (SF) 5 and 6 showed increased synthetic yields among tested enzymes. In particular, it was shown that FAEs belonging to SF6 generally transesterified aliphatic alcohols more efficiently while SF5 members preferred bulkier l-arabinose. Predicted surface properties and structural characteristics were correlated with the synthetic potential of selected tannase-related, acetyl-xylan-related, and lipase-related FAEs (SF1-2, -6, -7 members) based on homology modeling and small molecular docking simulations.

  • 50.
    Antonopoulou, Io
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hunt, Cameron
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Cerullo, Gabriella
    Department of Chemical Sciences, University of Naples "Federico II".
    Varriale, Simona
    Department of Chemical Sciences, University of Naples “Federico II”.
    Gerogianni, Alexandra
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Faraco, Vincenza
    Department of Chemical Sciences, University of Naples "Federico II".
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Tailoring the specificity of the type C feruloyl esterase FoFaeC from Fusarium oxysporum towards methyl sinapate by rational redesign based on small molecule docking simulations2018In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, no 5, article id e0198127Article in journal (Refereed)
    Abstract [en]

    The type C feruloyl esterase FoFaeC from Fusarium oxysporum is a newly discovered enzyme with high potential for use in the hydrolysis of lignocellulosic biomass but it shows low activity towards sinapates. In this work, small molecule docking simulations were employed in order to identify important residues for the binding of the four model methyl esters of hydroxycinnamic acids, methyl ferulate/caffeate/sinapate/p-coumarate, to the predicted structure of FoFaeC. Subsequently rational redesign was applied to the enzyme’ active site in order to improve its specificity towards methyl sinapate. A double mutation (F230H/T202V) was considered to provide hydrophobic environment for stabilization of the methoxy substitution on sinapate and a larger binding pocket. Five mutant clones and the wild type were produced in Pichia pastoris and biochemically characterized. All clones showed improved activity, substrate affinity, catalytic efficiency and turnover rate compared to the wild type against methyl sinapate, with clone P13 showing a 5-fold improvement in catalytic efficiency. Although the affinity of all mutant clones was improved against the four model substrates, the catalytic efficiency and turnover rate decreased for the substrates containing a hydroxyl substitution.

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