| 1. |
- Bünder, Anne, et al.
(author)
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CELLULOSE SYNTHASE INTERACTING 1 is required for wood mechanics and leaf morphology in aspen
- 2020
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In: The Plant Journal. - : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 103:5, s. 1858-1868
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Journal article (peer-reviewed)abstract
- Cellulose microfibrils synthesized by CELLULOSE SYNTHASE COMPLEXES (CSCs) are the main load‐bearing polymers in wood. CELLULOSE SYNTHASE INTERACTING1 (CSI1) connects CSCs with cortical microtubules, which align with cellulose microfibrils. Mechanical properties of wood are dependent on cellulose microfibril alignment and structure in the cell walls, but the molecular mechanism(s) defining these features is unknown. Herein, we investigated the role of CSI1 in hybrid aspen (Populus tremula × Populus tremuloides ) by characterizing transgenic lines with significantly reduced CSI1 transcript abundance. Reduction in leaves (50–80%) caused leaf twisting and misshaped pavement cells, while reduction (70–90%) in developing xylem led to impaired mechanical wood properties evident as a decrease in the elastic modulus and rupture. X‐ray diffraction measurements indicate that microfibril angle was not impacted by the altered CSI1 abundance in developing wood fibres. Instead, the augmented wood phenotype of the transgenic trees was associated with a reduced cellulose degree of polymerization. These findings establish a function for CSI1 in wood mechanics and in defining leaf cell shape. Furthermore, the results imply that the microfibril angle in wood is defined by CSI1 independent mechanism(s).
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| 2. |
- Bünder, Anne
(author)
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The biology and properties of wood for nanocellulose production
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Wood is a renewable and environmentally friendly raw material envisioned for the production of novel materials. In this interdisciplinary thesis project, I investigated genetic factors controlling cellulose biosynthesis, cellulose microfibril dimensions, wood mechanical properties and factors that influence nanocellulose extraction from wood. I show that RNA-interference-mediated reduction of the CELLULOSE SYNTHASE-INTERACTIVE 1 (CSI1), which is known to link the cellulose synthase complex (CSC) to cortical microtubules (cMTs), affects wood mechanical properties as well as fibre dimensions and cellulose degree of polymerization (DP) in hybrid aspen (Populus tremula x tremuloides). Furthermore, the reduced level of CSI1 was shown to negatively affect cellulose nanofibril (CNF) separation, possibly due to structural differences in cellulose microfibrils (CMFs) and/or cell wall matrix interactions. Additionally, alteration in cellulose DP and wood mechanical properties were found to be preserved in the manufactured CNF networks. In collaboration with material scientists, I also investigated the effect of tension wood and variations in wood lignin content on nanocellulose isolation and properties. We found that the cell wall structure and composition of the tension wood, negatively affect CNF isolation when using TEMPO-mediated oxidation followed by mechanical nanofibrillation. Unexpectedly, high wood lignin content facilitated CNF isolation, potentially through increased cell wall porosity caused by TEMPO-mediated delignification. Taken together, the results show that native wood properties affect CNF isolation as well as CNF properties and motivate for further genetic improvement of trees and wood as a raw material for nanocellulose production.
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| 3. |
- Dominguez, Pia Guadalupe, et al.
(author)
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Sucrose synthase determines carbon allocation in developing wood and alters carbon flow at the whole tree level in aspen
- 2021
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In: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 229:1, s. 186-198
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Journal article (peer-reviewed)abstract
- Despite the ecological and industrial importance of biomass accumulation in wood, the control of carbon (C) allocation to this tissue and to other tree tissues remain poorly understood. We studied sucrose synthase (SUS) to clarify its role in biomass formation and C metabolism at the whole tree level in hybrid aspen (Populus tremula x tremuloides). To this end, we analysed source leaves, phloem, developing wood, and roots ofSUSRNAitrees using a combination of metabolite profiling, 13CO2 pulse labelling experiments, and long-term field experiments. The glasshouse grownSUSRNAitrees exhibited a mild stem phenotype together with a reduction in wood total C. The 13CO2 pulse labelling experiments showed an alteration in the C flow in all the analysed tissues, indicating that SUS affects C metabolism at the whole tree level. This was confirmed when theSUSRNAitrees were grown in the field over a 5-yr period; their stem height, diameter and biomass were substantially reduced. These results establish that SUS influences C allocation to developing wood, and that it affects C metabolism at the whole tree level.
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| 4. |
- Jonasson, Simon, et al.
(author)
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Characteristics of Cellulose Nanofibrils from Transgenic Trees with Reduced Expression of Cellulose Synthase Interacting 1
- 2022
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In: Nanomaterials. - : MDPI. - 2079-4991. ; 12:19
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Journal article (peer-reviewed)abstract
- Cellulose nanofibrils can be derived from the native load-bearing cellulose microfibrils in wood. These microfibrils are synthesized by a cellulose synthase enzyme complex that resides in the plasma membrane of developing wood cells. It was previously shown that transgenic hybrid aspen trees with reduced expression of CSI1 have different wood mechanics and cellulose microfibril properties. We hypothesized that these changes in the native cellulose may affect the quality of the corresponding nanofibrils. To test this hypothesis, wood from wild-type and transgenic trees with reduced expression of CSI1 was subjected to oxidative nanofibril isolation. The transgenic wood-extracted nanofibrils exhibited a significantly lower suspension viscosity and estimated surface area than the wild-type nanofibrils. Furthermore, the nanofibril networks manufactured from the transgenics exhibited high stiffness, as well as reduced water uptake, tensile strength, strain-to-break, and degree of polymerization. Presumably, the difference in wood properties caused by the decreased expression of CSI1 resulted in nanofibrils with distinctive qualities. The observed changes in the physicochemical properties suggest that the differences were caused by changes in the apparent nanofibril aspect ratio and surface accessibility. This study demonstrates the possibility of influencing wood-derived nanofibril quality through the genetic engineering of trees.
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| 5. |
- Jonasson, Simon, et al.
(author)
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Comparison of tension wood and normal wood for oxidative nanofibrillation and network characteristics
- 2021
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In: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 28:2, s. 1085-1104
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Journal article (peer-reviewed)abstract
- Cellulose nanofibrils (CNFs) are top-down nanomaterials obtainable from abundant lignocelluloses. Despite recent advances in processing technologies, the effects of variations in the lignocellulose structure and composition on CNF isolation and properties are poorly understood. In this study, we compared the isolation of CNFs from tension wood (TW) and normal wood (NW) from Populus tremula (aspen). The TW has a higher cellulose content, native cellulose fibrils with a larger crystalline diameter, and less lignin than the NW, making it an interesting material for CNF isolation. The wood powders were oxidized directly by 2,2,6,6-tetramethylpiperidin-1-oxyl, and the morphology and mechanical behaviors of the nanofibril suspensions and networks were characterized. The TW was more difficult to fibrillate by both chemical and mechanical means. Larger nanofibrils (5–10 nm) composed of 1.2 nm structures were present in the TW CNFs, whereas the NW samples contained more of thin (1.6 nm) structures, which also comprised 77% of the solid yield compared to the 33% for TW. This difference was reflected in the TW CNF networks as decreased transmittance (15% vs. 50%), higher degree of crystallinity (85.9% vs. 78.0%), doubled toughness (11 MJ/m3) and higher elongation at break (12%) compared to NW. The difference was ascribed to greater preservation of the hierarchical, more crystalline microfibril structure, combined with a more cellulose-rich network (84% vs. 70%). This knowledge of the processing, structure, and properties of CNFs can facilitate the breeding and design of wood feedstocks to meet the increasing demand for nanoscale renewable materials.
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| 6. |
- Jonasson, Simon, et al.
(author)
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Isolation and characterization of cellulose nanofibers from aspen wood using derivatizing and non-derivatizing pretreatments
- 2020
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In: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 27:1, s. 185-203
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Journal article (peer-reviewed)abstract
- The link between wood and corresponding cellulose nanofiber (CNF) behavior is complex owing the multiple chemical pretreatments required for successful preparation. In this study we apply a few pretreatments on aspen wood and compare the final CNF behavior in order to rationalize quantitative studies of CNFs derived from aspen wood with variable properties. This is relevant for efforts to improve the properties of woody biomass through tree breeding. Three different types of pretreatments were applied prior to disintegration (microfluidizer) after a mild pulping step; derivatizing TEMPO-oxidation, carboxymethylation and non-derivatizing soaking in deep-eutectic solvents. TEMPO-oxidation was also performed directly on the plain wood powder without pulping. Obtained CNFs (44–55% yield) had hemicellulose content between 8 and 26 wt% and were characterized primarily by fine (height ≈ 2 nm) and coarser (2 nm < height < 100 nm) grade CNFs from the derivatizing and non-derivatizing treatments, respectively. Nanopapers from non-derivatized CNFs had higher thermal stability (280 °C) compared to carboxymethylated (260 °C) and TEMPO-oxidized (220 °C). Stiffness of nanopapers made from non-derivatized treatments was higher whilst having less tensile strength and elongation-at-break than those made from derivatized CNFs. The direct TEMPO-oxidized CNFs and nanopapers were furthermore morphologically and mechanically indistinguishable from those that also underwent a pulping step. The results show that utilizing both derivatizing and non-derivatizing pretreatments can facilitate studies of the relationship between wood properties and final CNF behavior. This can be valuable when studying engineered trees for the purpose of decreasing resource consumption when isolation cellulose nanomaterials.
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| 7. |
- Jonasson, Simon, et al.
(author)
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Mechanical-chemical nanofiber extractability of woodwith variable ultrastructure and composition throughone-pot oxidative pretreatments
- 2019
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In: 6<sup>th</sup> EPNOE International Polysaccharide Conference. - : European Polysaccharide Network of Excellence (EPNOE). ; , s. 114-114
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Conference paper (peer-reviewed)abstract
- Isolation of high value nanofibers from lignocellulosic feedstocks is a costly and resource intensive process. This stems from the complex structure of the raw material which contains hierarchical crystalline cellulose within hydrophobic lignin layers. This inherent structure makes inquiries regarding suitability of a certain lignocellulose for nanofibrillation difficult. Further nuances are present due to the common usage of both mechanical and chemical processing, often using pre-delignified wood as starting material.In this study we look at how the isolation of nanofibers is a↵ected by inherent wood properties by nanofibrillating wood from trees that has been physically stimulated to produce biomass with higher cellulose/lignin ratio and a different cell wall structure. Cryocrushed samples have been processed with i) mechanical, ii) chemical and iii) mechanical-chemical treatments, where (one-pot) direct TEMPO-catalyzed oxidation with different severity and high-pressure homogenization serve as controlled chemical and mechanical factors, respectively.The nanofibers have been characterized in suspension according to traditional procedures regarding degree of fibrillation, and then made into dense nanopapers for mechanical characterization. The material behavior is discussed in relation to the structure of the initial biomass and corresponding fibrillation efficiency. The results are presented in terms of both mechanical disintegration and chemical (carboxylation) derivatization.
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| 8. |
- Jonasson, Simon, et al.
(author)
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The Effect of High Lignin Content on Oxidative Nanofibrillation of Wood Cell Wall
- 2021
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In: Nanomaterials. - : MDPI. - 2079-4991. ; 11:5
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Journal article (peer-reviewed)abstract
- Wood from field-grown poplars with different genotypes and varying lignin content (17.4 wt % to 30.0 wt %) were subjected to one-pot 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl catalyzed oxidation and high-pressure homogenization in order to investigate nanofibrillation following simultaneous delignification and cellulose oxidation. When comparing low and high lignin wood it was found that the high lignin wood was more easily fibrillated as indicated by a higher nanofibril yield (68% and 45%) and suspension viscosity (27 and 15 mPa·s). The nanofibrils were monodisperse with diameter ranging between 1.2 and 2.0 nm as measured using atomic force microscopy. Slightly less cellulose oxidation (0.44 and 0.68 mmol·g−1) together with a reduced process yield (36% and 44%) was also found which showed that the removal of a larger amount of lignin increased the efficiency of the homogenization step despite slightly reduced oxidation of the nanofibril surfaces. The surface area of oxidized high lignin wood was also higher than low lignin wood (114 m2·g−1 and 76 m2·g−1) which implicates porosity as a factor that can influence cellulose nanofibril isolation from wood in a beneficial manner.
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