| 1. |
- Gullfot, Fredrika, 1967-
(author)
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Synthesis of xyloglucan oligo- and polysaccharides with glycosynthase technology
- 2009
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Licentiate thesis (other academic/artistic)abstract
- Xyloglucans are polysaccharides found as storage polymers in seeds and tubers, and as cross-linking glycans in the cell wall of plants. Their structure is complex with intricate branching patterns, which contribute to the physical properties of the polysaccharide including its binding to and interaction with other glycans such as cellulose. Xyloglucan is widely used in bulk quantities in the food, textile and paper making industries. With an increasing interest in technically more advanced applications of xyloglucan, such as novel biocomposites, there is a need to understand and control the properties and interactions of xyloglucan with other compounds, to decipher the relationship between xyloglucan structure and function, and in particular the effect of different branching patterns. However, due to the structural heterogeneity of the polysaccharide as obtained from natural sources, relevant studies have not been possible to perform in practise. This fact has stimulated an interest in synthetic methods to obtain xyloglucan mimics and analogs with well-defined structure and decoration patterns. Glycosynthases are hydrolytically inactive mutant glycosidases that catalyse the formation of glycosidic linkages between glycosyl fluoride donors and glycoside acceptors. Since its first conception in 1998, the technology is emerging as a useful tool in the synthesis of large, complex polysaccharides. This thesis presents the generation and characterisation of glycosynthases based on xyloglucanase scaffolds for the synthesis of well-defined homogenous xyloglucan oligo- and polysaccharides with regular substitution patterns.
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| 2. |
- Aitomäki, Yvonne, et al.
(author)
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Sounding Out Paper Pulp : Ultrasound Spectroscopy of Dilute Viscoelastic Fibre Suspensions Acoustics and Ultrasonics
- 2006
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Conference paper (other academic/artistic)abstract
- 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.
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| 3. |
- Sidorova, Ekaterina, 1986-
(author)
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Oil heat treatment of wood
- 2008
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In: 7th meeting of the Nordic-Baltic Network in Wood Material Science and Engineering. - Riga. - 9789984396750
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Conference paper (peer-reviewed)abstract
- The investigation of thermal treatment of wood has led to the improvement of heat treatment with vegetable oils. The aim of this work has been to study the oil absorption of wood during the process of oil heat treatment. This work has included the heat treatment of spruce, pine (heartwood and sapwood) and aspen in rape seed oil. The heat treatment was performed in the deep fryer at 180, 210 and 240°C during 30, 60 and 120 minutes. Two sets of samples were run, the first one was heat treated and left to cool in the air, the second one was heat treated and directly cooled in the oil bath for 1 hour. At 180°C there was a trend of increasing oil absorption during the heat treatment with the increasing the treatment time for all species. At 210°C the percentage of mass growth was reducing with increasing the time of the process. At 240°C all species lost the weight and the percentage of weight loss was increasing proportionally with increasing heat treatment time. During the heat treatment aspen had the highest mass increase and pine heartwood had the lowest. Results showed that wood absorbed significantly more oil in the stage of cooling in oil than during heat treatment. All species had a tendency to have approximately the same oil pick up during storing in the oil bath after the heat treatment at one temperature, so the heat treatment time did not have an effect on the oil absorption in the stage of cooling. The oil pick up during the stage of cooling had the lowest values for all species treated at 240°, because all the species lost the mass during the heat treatment at 240°. The colour changed during heat treatment and depended mainly on the heat treatment temperature. The darkness was increasing proportionally with increasing the thermal treatment temperature. The colour varied among the species.
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| 4. |
- Kumar, Ashok, et al.
(author)
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Integrated bioprocess for the production and isolation of urokinase from animal cell culture using supermacroporous cryogel matrices
- 2006
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In: Biotechnology and Bioengineering. - Hoboken, NJ : Wiley. - 1097-0290 .- 0006-3592. ; 93:4, s. 636-646
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Journal article (peer-reviewed)abstract
- An integrated cell cultivation and protein product separation process was developed using a new type of supermacroporous polyacrylamide gel, called cryogel (pAAm-cryogel) support matrix. Human fibrosarcoma HT1080 and human colon cancer HCT116 cell lines were used to secrete urokinase (an enzyme of immense therapeutic utility) into the culture medium. The secreted protein was isolated from the circulating medium using a chromatographic capture column. A pAAm cryogel support with covalently coupled gelatin (gelatin-pAAm cryogel) was used for the cultivation of anchorage dependent cells in the continuous cell culture mode in 5% carbon dioxide atmosphere. The cells were attached to the matrix within 4-6 h of inoculation and grew as a tissue sheet inside the cryogel matrix. Continuous urokinase secretion into the circulating medium was monitored as a parameter of growth and viability of cells inside the bioreactor. No morphological changes were observed in the cells eluted from the gelatin-cryogel support and re-cultured in T-flask. The gelatin-pAAm cryogel bioreactor was further connected to a pAAm cryogel column carrying Cu(II)-iminodiacetic acid (Cu(II)-IDA)-ligands (Cu(II)-IDA-pAAm cryogel), which had been optimized for the capture of urokinase from the conditioned medium of the cell lines. Thus an automated system was built, which integrated the features of a hollow fiber reactor with a chromatographic protein separation system. The urokinase was continuously captured by the Cu(II)-IDA-pAAm cryogel column and periodically recovered through elution cycles. The urokinase activity increased from 250 PU/mg in the culture fluid to 2,310 PU/mg after recovery from the capture column which gave about ninefold purification of the enzyme. Increased productivity was achieved by operating integrated bioreactor system continuously for 32 days under product inhibition free conditions during which no back-pressure or culture contamination was observed. A total 152,600 Plough units of urokinase activity was recovered from 500 mL culture medium using 38 capture columns over a period of 32 days. (c) 2006 Wiley Periodicals, Inc.
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| 5. |
- Terashima, N., et al.
(author)
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2D-NMR (HSQC) difference spectra between specifically C-13-enriched and unenriched protolignin of Ginkgo biloba obtained in the solution state of whole cell wall material
- 2009
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In: Holzforschung. - 1437-434X .- 0018-3830. ; 63:4, s. 379-384
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Journal article (peer-reviewed)abstract
- In the structural analysis of lignins by C-13-NMR, signal overlap limits definitive assignment and accurate intensity measurement. Selective labeling by C-13-enrichment of a specific carbon in lignin enhances its signal intensity in the spectrum. Further enhancement of the specifically labeled carbons can be realized via difference spectra created from the enriched and unenriched samples. Difference 2D C-13-H-1 correlation (HSQC) NMR spectra, derived from the spectra of specifically C-13-enriched lignin model polymers (so-called dehydrogenation polymers) and their unenriched counterparts, take advantage of the enhanced dispersion afforded by both C-13 and H-1 chemical shifts, diminishing the difficulties arising from the signal-overlap problem and aiding in definitive signal assignments. In this research, protolignin in xylem cell walls was specifically C-13-enriched at all of the individual phenylpropanoid side-chain carbons by feeding C-13-enriched coniferins to growing stems of Ginkgo biloba. The whole xylem fractions containing C-13-enriched and unenriched protolignins were dissolved in a mixture of N-methylimidazole and DMSO, and then acetylated. Solution state 2D-NMR (HSQC) spectra of the acetylated whole cell wall were acquired. Difference spectra between the walls containing C-13-enriched and unenriched lignins afforded simplified 2D spectra in which well-separated signals were assigned exclusively to the specifically enriched carbons. This novel NMR technique provides a useful tool for elucidation of entire protolignin in the cell wall of ginkgo xylem.
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| 6. |
- Alemandar, Ayse, et al.
(author)
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The effect of decreased fiber size in wheat straw/polyvinyl alchol composites
- 2009
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In: Journal of Biobased Materials and Bioenergy. - : American Scientific Publishers. - 1556-6560 .- 1556-6579. ; 3:1, s. 75-80
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Journal article (peer-reviewed)abstract
- 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.
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| 7. |
- Alemdar, Ayse, et al.
(author)
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Reinforcement capability of wheat straw fibers from micro to nano size
- 2007
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In: 9th International Conference on Wood & Biofiber Plastic Composites. - Madison, Wis : Forest Products Society. - 1892529505
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Conference paper (peer-reviewed)abstract
- 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.
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| 8. |
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| 9. |
- Bengtsson, Magnus, et al.
(author)
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Durability and mechanical properties of silane cross-linkedwood thermoplastic composites
- 2007
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In: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 67:13, s. 2728-2738
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Journal article (peer-reviewed)abstract
- In this study, silane cross-linked wood-polyethylene composite profiles were manufactured by reactive extrusion. These composites were evaluated regarding their durability and mechanical properties in comparison with two non-cross-linked wood-polyethylene composites. An addition of only 2% w/w of silane solution during manufacturing was enough to achieve almost 60% degree of cross-linking after curing. The cross-linked composites showed flexural toughness superior to the non-cross-linked composites. The cross-linked composites also absorbed less moisture during a boiling test in water and this was an indirect evidence of improved interfacial adhesion. After accelerated weathering for 1000-3000 h the general trend was a decrease in flexural modulus and strength of both the non-cross-linked and cross-linked composites. The decrease in modulus seemed to be lower for the cross-linked composites while the decrease in strength seemed to be higher compared to the non-cross-linked composites. Weathering also resulted in a considerable colour fading of the composites. Water absorption-freeze-thaw cycling decreased the flexural modulus of non-cross-linked composites considerably while there was no statistical decrease in modulus for the cross-linked composites. There was only an insignificant decrease in strength for the composites after the water absorption-freeze-thaw cycling.
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| 10. |
- Bengtsson, Magnus, et al.
(author)
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Extrusion and mechanical properties of highly filled cellulose fibre-polypropylene composites
- 2007
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In: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 38:8, s. 1922-1931
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Journal article (peer-reviewed)abstract
- This study focused on manufacturing of highly filled cellulose fibre-polypropylene composites and evaluation of the mechanical properties of the composites. Cellulose fibre reinforced polypropylene composites with up to 60 wt-% of fibres with and without coupling agent were manufactured by extrusion. In order to achieve consistent feeding of the fibres into the extruder a pelletization technique was used where the fibres were pressed into pellets. Two commercial grades of cellulose fibres were used in the study, bleached sulfite and bleached kraft fibres. Fibre dimension measurements showed that the pelletization process and extrusion at high fibre loading caused the most severe fibre breakage. Flexural testing showed that increased fibre loading made the composites stiffer but reduced the toughness. Addition of maleic anhydride grafted coupling agent increased the stiffness and strength of the composites significantly. In general, there was no significant difference in the mechanical properties between the composites with kraft and sulfite fibres. Scanning electron microscopy showed that addition of coupling agent improved the interfacial adhesion between the fibres and polypropylene matrix.
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