| 1. |
- Anasontzis, George E, 1980
(författare)
-
Biomass modifying enzymes: From discovery to application
- 2012
-
Ingår i: Oral presentation at the Chalmers Life Science AoA conference.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- It has now been realized that the road towards the bio-based economy is a one-way street, leaving gradually the oil-based technology and driving slowly towards a more sustainable society. The current non-biodegradable hydrocarbon fuels and plastics will be replaced by new products which will derive from natural and renewable resources. The synthesis of such biofuels and biochemicals is still challenged by the difficulties to cost efficiently degrade lignocellulosic material to fermentable sugars or to isolate the intact polymers. Biomass degrading and modifying enzymes play an integral role both in the separation of the polymers from the wood network, as well as in their subsequent modification, prior to further product development.Our group interests focus on all levels of applied enzyme research of biomass acting enzymes: Discovery, assay development, production and application. Relevant examples will be provided: What is our strategy for discovering novel microorganisms and enzymes from the tropical forests and grasslands of Vietnam? How do we design novel real-world assays for enzyme activity determination? Which are the bottlenecks in the enzymatic cellulose hydrolysis? How enzymes can be used to produce high added value compounds from biomass?
|
|
| 2. |
- Martinez Avila, Hector, 1985, et al.
(författare)
-
Biocompatibility evaluation of densified bacterial nanocellulose hydrogel as an implant material for auricular cartilage regeneration
- 2014
-
Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 98:17, s. 7423-7435
-
Tidskriftsartikel (refereegranskat)abstract
- Bacterial nanocellulose (BNC), synthesized by the bacterium Gluconacetobacter xylinus, is composed of highly hydrated fibrils (99 % water) with high mechanical strength. These exceptional material properties make BNC a novel biomaterial for many potential medical and tissue engineering applications. Recently, BNC with cellulose content of 15 % has been proposed as an implant material for auricular cartilage replacement, since it matches the mechanical requirements of human auricular cartilage. This study investigates the biocompatibility of BNC with increased cellulose content (17 %) to evaluate its response in vitro and in vivo. Cylindrical BNC structures (48 Au 20 mm) were produced, purified in a built-in house perfusion system, and compressed to increase the cellulose content in BNC hydrogels. The reduction of endotoxicity of the material was quantified by bacterial endotoxin analysis throughout the purification process. Afterward, the biocompatibility of the purified BNC hydrogels with cellulose content of 17 % was assessed in vitro and in vivo, according to standards set forth in ISO 10993. The endotoxin content in non-purified BNC (2,390 endotoxin units (EU)/ml) was reduced to 0.10 EU/ml after the purification process, level well below the endotoxin threshold set for medical devices. Furthermore, the biocompatibility tests demonstrated that densified BNC hydrogels are non-cytotoxic and cause a minimal foreign body response. In support with our previous findings, this study concludes that BNC with increased cellulose content of 17 % is a promising non-resorbable biomaterial for auricular cartilage tissue engineering, due to its similarity with auricular cartilage in terms of mechanical strength and host tissue response.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Stépán, Agnes, 1985, et al.
(författare)
-
Enzymatic Transformation of Hemicelluloses to Bioplastics
- 2012
-
Ingår i: 243rd ACS National Meeting, 25-29 March 2012, San Diego, CA, USA.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Hemicelluloses being the second most abundant biopolymer on Earth are getting more attention in the recent years for having a great potential as a renewable source for materials, fine chemicals and fuels. The focus of this study is to modify molecular architecture of spruce arabinoglucuronoxylan (AGX) and to gain better understanding of structure-material properties relationships. Chemical acetylation and gradient debranching of arabinoxylan has been carried out and material properties have been evaluated. The recent work is more focused on enzymatic acetylation and acylation. Most of our enzymatic modifications are based on enzymes with a proven record in biocatalytic reactions. In parallel, we target the use of more specific acting enzymes as well. These enzymes are commercially not available yet, so this part includes enzyme cloning and production. The desired product is a thermoplastic biomaterial suitable for packaging or as binder / matrix in a biocomposite.
|
|
| 8. |
|
|
| 9. |
- Aakeröy, Christer, et al.
(författare)
-
Co-crystal screening of diclofenac
- 2011
-
Ingår i: Pharmaceutics. - : MDPI AG. - 1999-4923. ; 3:3, s. 601-614
-
Tidskriftsartikel (refereegranskat)
|
|
| 10. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Accelerated Mold Test on Dried Pine Sapwood Boards : Impact of Contact Heat Treatment
- 2013
-
Ingår i: Journal of wood chemistry and technology. - : Taylor & Francis. - 0277-3813 .- 1532-2319. ; 33:3, s. 174-187
-
Tidskriftsartikel (refereegranskat)abstract
- 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). An 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 that accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth were 170°C for 10 min. However, 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.
|
|
| 11. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression
- 2013
-
Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:24, s. 8571-8579
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 12. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Development of a new rapid method for mould testing in a climate chamber : preliminary tests
- 2013
-
Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 71:4, s. 451-461
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 13. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood
- 2013
-
Ingår i: Wood Science and Technology. - : Springer Science and Business Media LLC. - 0043-7719 .- 1432-5225. ; 47:3, s. 499-513
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 14. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy
- 2013
-
Ingår i: Journal of Wood Science. - : Springer. - 1435-0211 .- 1611-4663. ; 59:1, s. 57-66
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 15. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives
- 2012
-
Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 44:1, s. 85-93
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 16. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood : Impact of drying, thermal modification, and copper-based preservative
- 2013
-
Ingår i: International Biodeterioration & Biodegradation. - : Elsevier. - 0964-8305 .- 1879-0208. ; 85, s. 284-288
-
Tidskriftsartikel (refereegranskat)abstract
- 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 such as the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are 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 and planing off the nutrient enriched evaporation surfaces.
|
|
| 17. |
- Ahmed, Sheikh Ali, et al.
(författare)
-
Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine : Impact of wood structure and resin allocation
- 2012
-
Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 66:2, s. 251-258
-
Tidskriftsartikel (refereegranskat)abstract
- 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 un-even 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.
|
|
| 18. |
|
|
| 19. |
- Aitomäki, Yvonne, et al.
(författare)
-
Cellulose nanofibril nanocomposites processing
- 2013
-
Ingår i: Production and Applications of Cellulose Nanomaterials. - Peachtree Corners, GA : TAPPI Press. - 9781595102249 ; , s. 271-274
-
Bokkapitel (refereegranskat)abstract
- 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.
|
|
| 20. |
- Aitomäki, Yvonne, et al.
(författare)
-
Estimating material properties of solid and hollow fibers in suspension using ultrasonic attenuation
- 2013
-
Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 60:7, s. 1424-1434
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 21. |
- Aitomäki, Yvonne, et al.
(författare)
-
Impregnation of cellulose nanofibre networks with a thermoplastic polymer
- 2013
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 22. |
- Aitomäki, Yvonne, et al.
(författare)
-
Novel reactive bicomponent fibres : Material in composite manufacturing
- 2012
-
Ingår i: Journal of Nanostructured Polymers and Nanocomposites. - 1790-4439. ; 8:1, s. 5-11
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 23. |
- Aitomäki, Yvonne, et al.
(författare)
-
Quantifying reinforcing efficiency of nanocellulose fibres
- 2013
-
Ingår i: Processing of fibre composites-challenges for maximum materials performance. - Risö : Dept. of Wind Energy, Technical University of Denmark. - 9788792896513 ; , s. 149-160
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 24. |
- Aitomäki, Yvonne, et al.
(författare)
-
Reinforcing efficiency of nanocellulose in polymers
- 2014
-
Ingår i: Reactive & functional polymers. - : Elsevier BV. - 1381-5148 .- 1873-166X. ; 85, s. 151-156
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 25. |
|
|
