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Poly(ethylene-alt-maleic anhydride), PEMA, and modified PEMA with pendent poly(ethylene glycol) oligomers (PEG3, PEG10, PEG20) in anhydrous acetone were grafted onto mechanically produced cellulose microfibrils, CNFs. The grafted CNFs had up to 4.7 mmol/g of carboxylic acid groups from the hydrolyzed PEMA. Before and after grafting, the concentrations of individualized microfibrils were low (< 10% wt/wt). Atomic force microscopy revealed that the main CNFs components were intermeshed microfibrils, microfibril bundles, and ribbons a few μm wide. Mastersizer particle size distributions were usually bimodal, with 10–20 μm and 100–200 μm peaks. We proposed that the smaller peaks were individualized ribbons plus small aggregates, and the larger ones were flocculated ribbons and microfibrils. Based on the images of dried ribbons adsorbed on cationic glass and the shapes of aqueous ribbons sitting near the non-adhesive anionic glass, the PEMA-treated ribbons were stiffer than the PEMA-PEG grafted ribbons. Perhaps the high anhydride concentration on PEMA facilitated more crosslinking of the CNFs surfaces compared to PEMA-PEG polymers with about 10 times less reactive anhydride groups. The presence of grafted PEMAc or PEMAc with pendent PEG chains had little influence on CNFs dispersibility. [ABSTRACT FROM AUTHOR]

The infrared beamline at BESSY II storage ring was upgraded recently to extend the capabilities of infrared microscopy. The endstations available at the beamline are now facilitating improved characterization of molecules and materials at different length scales and time resolutions. Here, the current outline of the beamline is reported and an overview of the endstations available is given. In particular, the first results obtained by using a new microscope for nano-spectroscopy that was implemented are presented. The capabilities of the scattering-type near-field optical microscope (s-SNOM) are demonstrated by investigating cellulose microfibrils, representing nanoscopic objects of a hierarchical structure. It is shown that the s-SNOM coupled to the beamline allows imaging to be performed with a spatial resolution of less than 30 nm and infrared spectra to be collected from an effective volume of less than 30 nm × 30 nm × 12 nm. Potential steps for further optimization of the beamline performance are discussed.

The infrared beamline at BESSY II storage ring was upgraded recently to extend the capabilities of infrared microscopy. The endstations available at the beamline are now facilitating improved characterization of molecules and materials at different length scales and time resolutions. Here, the current outline of the beamline is reported and an overview of the endstations available is given. In particular, the first results obtained by using a new microscope for nano-spectroscopy that was implemented are presented. The capabilities of the scattering-type near-field optical microscope (s-SNOM) are demonstrated by investigating cellulose microfibrils, representing nanoscopic objects of a hierarchical structure. It is shown that the s-SNOM coupled to the beamline allows imaging to be performed with a spatial resolution of less than 30 nm and infrared spectra to be collected from an effective volume of less than 30 nm x 30 nm x 12 nm. Potential steps for further optimization of the beamline performance are discussed. [ABSTRACT FROM AUTHOR]

We used to consider native cellulose to be composed of microfibrils continuously crystalline along the chain direction with constant lateral dimension. To sulfate the surface of cellulose microfibrils, we activated cotton fibers by pre-swelling in water or DMF followed by immersion in an excess amount of sulfamic acid in dimethylformamide (DMF) in heterogeneous conditions. The degree of sulfation was followed by elemental analysis and conductometric titration, while the structural changes associated with the sulfation and the homogenization were investigated by infrared spectroscopy, solid-state NMR, and X-ray diffraction. The initial sulfation of the cellulose surface was well described as a first order reaction with a kinetic constant of 2 × 10 - 3 s - 1 at 80 °C using 3.6% sulfamic, indicating that about half of the available hydroxy groups were sulfated within the first 5 min. A water pre-swelling step, followed by solvent exchange with DMF, increased the amount of available hydroxy groups by up to a factor of two. At long reaction times, there was a gradual increase in the degree of sulfation beyond the initially available surface by up to 20% during the two hours reaction investigated. FTIR and solid-state NMR spectra both suggest the reaction of surface primary hydroxy groups with sulfamic acid. While the apparent lateral crystallite size of cotton is unaffected by sulfation treatment, X-ray diffraction suggested that homogenization resulted in cellulose nanofibers (CNFs) with a crystallite width below 3 nm, much smaller than the initial cellulose microfibrils (6–7 nm). This apparent crystallite splitting during homogenization suggests that cotton microfibrils have an intertwined polycrystalline structure, rather than being monocrystalline along the whole length. [ABSTRACT FROM AUTHOR]

The mechanical properties of native cellulose are critical for understanding the properties of natural biomaterials. To investigate the elastic moduli of the cellulose crystalline fraction an isotropic mechanical load using hydrostatic pressure ranging from 0.01 to 0.5 GPa was applied to flax fibers, pine wood and tension wood samples. The response of the crystalline part was monitored by using microfocused synchrotron radiation. The compressibility of the crystalline fraction of native cellulose was anisotropic and dependent on the crystal size and possibly on the composition of the sample. The compressibilities along the [001] direction, where covalent bonds hold the cellulose chains together, varied between 2.1 and 2.9 TPa−1 for the different samples and confirm similar values found for cotton fibres. However, the compressibilities along the [100]-direction range from 56.2 TPa−1 to 63.5 TPa−1, slightly exceeding the previously determined value of 50 TPa−1, which can possibly be attributed to differences between individual samples. [ABSTRACT FROM AUTHOR]

Poly(butylene adipate-co-terephthalate) (PBAT) is one of the most suitable aliphatic–aromatic co-polyesters to replace traditional plastics due to its excellent properties and biodegradability. However, the relatively low mechanical properties limit its large-scale application. Nanocellulose has been attempted to be chemically modified and used to enhance PBAT, but few significant results have been achieved. In this study, three octadecylamine-modified carboxyethyl cellulose microfibrils (OC-CMFs) with different degrees of substitution (DS) were successfully prepared and used to enhance PBAT. The microstructure, chemical structure, hydrophobicity, and thermal stability of the prepared OC-CMFs, as well as the mechanical properties, microstructure, and thermal properties of the OC-CMFs/PBAT composites were characterized. The results show that OC-CMFs have high hydrophobicity, with a water contact angle of up to 132.2°, making them highly dispersed and compatible in the PBAT matrix. When 0.5 wt% OC-CMF with a DS of 0.22 was added, the tensile strength of PBAT increased by 47.8%, while the elongation at break significantly increased by 49.0%. The significant improvement in the PBAT's mechanical properties will help expand its application range and further promote its substitution for non-biodegradable plastics. [ABSTRACT FROM AUTHOR]

The pursuit of an environmentally sustainable manufacturing process requires the substitution of less damaging and recyclable solutions for harmful reagents. This study aims to assess the effectiveness of using cellulose microfibrils synthesized via different hydrolysis reactions as reinforcing agents in polyvinyl alcohol (PVA) at varying concentrations. The investigation explores the morphology, thermal properties, and chemical behavior of the cellulose particles. The cellulose microfibrils (CMFs) produced using citric acid exhibited the highest yield and aspect ratio. Notably, particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles displaying the maximum thermal degradation temperature. Subsequently, cast films of PVA reinforced with the cellulose microfibrils underwent comprehensive analyses, including Fourier transfer infrared (FTIR) spectroscopy, thermal degradation temperature (Td), differential scanning calorimetry (DSC), and tensile strength tests. The thermal behavior of cast films experienced notable changes with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures, along with a rise in the degree of crystallinity. The incorporation of cellulose particles led to a substantial improvement in mechanical properties. Films containing CMF displayed higher Young's modulus, and the sample incorporating 5% CMF derived from citric acid exhibited the most significant increase in modulus. [ABSTRACT FROM AUTHOR]

The present investigation demonstrated that through microwave treatment of natural fiber wastes, cellulose microfibrils with a purity of 86.82% by weight, a crystallinity percentage of 92.5%, lengths from 1 to 15 mm, and diameters between 7 and 12 µm are obtained. These results were obtained with a one-step methodology, where Agave fibers were suspended in ethylene glycol and irradiated for 5 min with a constant power of 200 W and temperature of 250 °C. In-situ analyses (heating rate, pressure, and aspect ratio of the reaction vial) performed during microwave irradiation, as well as the characterization (thermal, chemical, and morphological) of the treated agave fibers, indicated that dielectric heating of the components of the agave fibers (waxes, pectin, hemicellulose, lignin) produces their depolymerization and leaching towards the reaction medium (ethylene glycol) until their defibration is achieved. The reaction kinetics at different temperatures and times showed that the purification of the fibers starts at 12,000 W. However, to finally obtain the microfibrils, it is necessary to apply 69,812 W. This process has the advantage that the fiber does not have to be treated with chemical substances or mechanical processes before the microwave treatment. Moreover, no additives, reducers, or catalysts are used during or after the treatment, which makes it a novel and optimal process to produce highly pure and crystalline cellulose microfibrils for high-value-added applications. [ABSTRACT FROM AUTHOR]

X-ray scattering methods allow efficient characterization of cellulosic materials, but interpreting their results is challenging. By creating molecular dynamics models of cellulose microfibrils and calculating the scattering from them, we investigated how different properties of the structures affect their scattering intensities. We studied the effects of hemicelluloses and crystal size on small-angle and wide-angle X-ray scattering (SAXS, WAXS). Microfibril models with and without surface-bound hemicelluloses were built based on the chemical composition of spruce secondary cell walls. The effect of fibril size was investigated by comparing the scattering from fibrils with 14 to 40 cellulose chains. The hemicelluloses appeared in the SAXS region as an increase in the fibril radius and as a clear contribution of a shell around the fibril. The hemicelluloses also increased the crystal size as determined from the broadening of the 200 diffraction peak of cellulose I β . The SAXS and WAXS analysis provided consistent estimates for the size of the microfibrils, and their special features and challenges were discussed. In particular, the results of 18-chain microfibrils were consistent with prior experimental results. Carrying out the simulations in wet and dry environments had the most pronounced effect on fibrils with a hemicellulose coating. Twisting of the fibril had very little impact on most properties, except for a minor effect on the WAXS peaks. The results allow for more correct interpretation of experimental scattering results, leading to more accurate descriptions of microfibril structures in natural and processed cellulosic materials. [ABSTRACT FROM AUTHOR]

Scanning X-ray microdiffraction is applied to determine the structural variations of cellulose microfibrils among the fiber cells, vessel cells and ray cells of beechwood. A longitudinal section of beechwood was raster scanned with an X-ray microbeam. This allows to collect diffraction patterns from cell walls of distinct cell types. While the diffraction patterns from fiber cells are dominated by the cellulose signal with a longitudinal orientation, the diffraction patterns from ray and vessel cells show transversal fiber alignment, however to a lower degree of orientation. Moreover, the scattering pattern at small angle region of ray and vessel cells become less pronounced than to fiber cells. These results suggest that the crystalline cellulose of fiber cells has a completely different structure at the meso and molecular level when compared to ray and vessel cellulose within beechwood. [ABSTRACT FROM AUTHOR]

Physcomitrium patens is a good model system to study the structure and function relationships of cellulose synthase (CESA) proteins since the life cycle of moss is short and genetic modification is relatively easy. Here, we report a microscopic sum frequency generation (SFG) vibrational spectroscopy analysis of P. patens leaves in a never-dried and fully hydrated state. Using imaging-SFG spectroscopy, cellulose microfibril (CMF) organization in the midrib, laminar, and marginal regions of the gametophore leaf were analyzed separately. The azimuth angle dependence of SFG signals showed that CMFs in the thick stereid cell walls in the midrib are highly aligned along the microfibril angle of ~ 30° with respect to the midrib axis. CMFs in the marginal cell walls also are preferentially tilted toward the longitudinal axis of leaf with the characteristic features of secondary cell walls. On the other hand, CMFs in the lamina cell walls have no preferential orientation and their SFG intensity is low, which is consistent with the primary cell wall property. The thick walls and highly aligned CMFs in the midrib and marginal cells of P. patens leaves are consistent with their support function. [ABSTRACT FROM AUTHOR]

Carbohydrate binding modules (CBMs) are noncatalytic domains that assist tethered catalytic domains in substrate targeting. CBMs have therefore been used to visualize distinct polysaccharides present in the cell wall of plant cells and tissues. However, most previous studies provide a qualitative analysis of CBM‐polysaccharide interactions, with limited characterization of engineered tandem CBM designs for recognizing polysaccharides like cellulose and limited application of CBM‐based probes to visualize cellulose fibrils synthesis in model plant protoplasts with regenerating cell walls. Here, we examine the dynamic interactions of engineered type‐A CBMs from families 3a and 64 with crystalline cellulose‐I and phosphoric acid swollen cellulose. We generated tandem CBM designs to determine various characteristic properties including binding reversibility toward cellulose‐I using equilibrium binding assays. To compute the adsorption (nkon) and desorption (koff) rate constants of single versus tandem CBM designs toward nanocrystalline cellulose, we employed dynamic kinetic binding assays using quartz crystal microbalance with dissipation. Our results indicate that tandem CBM3a exhibited the highest adsorption rate to cellulose and displayed reversible binding to both crystalline/amorphous cellulose, unlike other CBM designs, making tandem CBM3a better suited for live plant cell wall biosynthesis imaging applications. We used several engineered CBMs to visualize Arabidopsis thaliana protoplasts with regenerated cell walls using confocal laser scanning microscopy and wide‐field fluorescence microscopy. Lastly, we also demonstrated how CBMs as probe reagents can enable in situ visualization of cellulose fibrils during cell wall regeneration in Arabidopsis protoplasts. [ABSTRACT FROM AUTHOR]

Significant efforts have been made over the past decade to facilitate the recognition of environmentally friendly packaging and promote sustainability. Yet, consumers remain confused by the excess of labels and claims used to communicate sustainability. In our previous work, we modified the appearance of recycled fibre‐based packaging by incorporating visible particles of fibre‐based waste. This strategy enabled consumers to better identify packages with a high recyclability level, enhancing their environmental perception towards sustainable products. However, the incorporation of such large waste particles proved to be detrimental to the mechanical properties of the paperboards. In this study, we further investigate the influence of the physicochemical properties of the added fibre‐based waste on packaging performance. Using a similar strategy to enhance the environmental perception, we herein studied the effect of mixed office waste (MOW), old magazines (OMG), and polylactic acid (PLA) paper cups. The presence of hydrophobic and difficult‐to‐process and difficult‐to‐disperse waste, such as the PLA paper cups, significantly altered the mechanical performance of the paperboards, whereas more hydrophilic and easy‐to‐disintegrate waste (MOW and OMG) had a lesser effect regardless of the size of the particles. Strength agents such as cationic starch (CS) and cellulose microfibrils (CMFs) successfully restored the properties of the paperboards containing MOW and OMG but were less effective for PLA paper cups. A multi‐ply strategy overcame the limitations of CS and CMFs using the redesigned paperboard as an outer ply for aesthetic purposes and a 100% recycled inner ply for restoring strength. [ABSTRACT FROM AUTHOR]

This study investigates eco-friendly membrane biocomposites derived from biomass, utilizing cellulose microfibrils (CMF) as the main membrane material. Cellulose nanocrystals (CNC), isolated from rice husk, were added as reinforcing fillers in CMF flat sheet membranes. CNC with concentrations of 0%, 10%, 20%, and 30% were employed. Scanning electron microscopy images revealed that CNC influenced the surface profile and the pore structure of the membranes, reducing the porosity by 23%. The empty areas formed by CMF interaction were effectively filled by CNC. This modified membrane resulted in an increase in NaCl rejection of up to 16%. Dynamic water contact angle demonstrated the role of CNC in enhancing permeability, with a shorter spreading time of 13 min. It was also confirmed by the highest flux of 351 L/m − 2h−1 under pure water flux conditions. Mechanical properties were significantly improved, with a 125% increase in tensile strength and a modulus of 329 MPa. The distribution of CNC within the membranes filled pores and enhanced CMF interaction, facilitated by abundant hydroxyl groups in CNC. Overall, this study highlights the potential of eco-friendly membrane biocomposites derived from biomass, offering valuable insights for the development of sustainable and efficient membrane materials.

The pursuit of an environmentally sustainable manufacturing process requires the substitution of less damaging and recyclable solutions for harmful reagents. This study aims to assess the effectiveness of using cellulose microfibrils synthesized via different hydrolysis reactions as reinforcing agents in polyvinyl alcohol (PVA) at varying concentrations. The investigation explores the morphology, thermal properties, and chemical behavior of the cellulose particles. The cellulose microfibrils (CMFs) produced using citric acid exhibited the highest yield and aspect ratio. Notably, particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles displaying the maximum thermal degradation temperature. Subsequently, cast films of PVA reinforced with the cellulose microfibrils underwent comprehensive analyses, including Fourier transfer infrared (FTIR) spectroscopy, thermal degradation temperature (Td), differential scanning calorimetry (DSC), and tensile strength tests. The thermal behavior of cast films experienced notable changes with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures, along with a rise in the degree of crystallinity. The incorporation of cellulose particles led to a substantial improvement in mechanical properties. Films containing CMF displayed higher Young’s modulus, and the sample incorporating 5% CMF derived from citric acid exhibited the most significant increase in modulus.

All plant cells are surrounded by a cell wall that provides cohesion, protection, and a means of directional growth to plants. Cellulose microfibrils contribute the main biomechanical scaffold for most of these walls. The biosynthesis of cellulose, which typically is the most prominent constituent of the cell wall and therefore Earth's most abundant biopolymer, is finely attuned to developmental and environmental cues. Our understanding of the machinery that catalyzes and regulates cellulose biosynthesis has substantially improved due to recent technological advances in, for example, structural biology and microscopy. Here, we provide a comprehensive overview of the structure, function, and regulation of the cellulose synthesis machinery and its regulatory interactors. We aim to highlight important knowledge gaps in the field, and outline emerging approaches that promise a means to close those gaps. Cellulose forms the primary biomechanical scaffold of plant cell walls, making it the most abundant biopolymer on Earth. This review provides a comprehensive summary of important biochemical structures and protein dynamics, as well as emerging challenges and questions concerning cellulose synthesis. [ABSTRACT FROM AUTHOR]

It is an interesting research topic to study the interfacial interactions between hemicellulose and cellulose, specifically how hemicellulose's structure affects its binding to cellulose nanofibers. Our research proposes that dispersion interaction play an important role in this interfacial interaction, more so than electrostatic forces when considering the adherence of cellulose to xylan. To quantify these interactions, the Atomic Force Microscope (AFM) colloidal probe technique is applied to measure the intermolecular forces between cellulose nanofibers, which are attached to the probe and xylan. These measured forces are then analyzed in relation to the length, diameter and functional groups of the nanocellulose, as well as the molecular weight and side chains of the xylan. Moreover, the predominance of dispersion forces by contrasting the adhesive forces before and after the grafting of a large nonpolar group onto xylan. This modification significantly reduces contact between the cellulose and xylan backbone, thereby markedly diminishing the dispersion interactions. Parallel to the AFM experiments, molecular dynamics (MD) simulations corroborate the experimental results and support our hypotheses. Collectively, these findings contribute to a deeper understanding of polysaccharide interactions within lignocellulose. Description:The experimental results were also validated using molecular dynamics simulations, indicating that dispersion interactions play an integral role between cellulose microfibrils and xylan. [Display omitted] • Colloidal probe technique and MD simulation to study cellulose-xylan interaction • Experiments and simulations prove dispersion interactions to be dominant. • The side chains of xylan have little effect on xylan-cellulose interactions. [ABSTRACT FROM AUTHOR]

Plant cell deformation is a mechanical process that is driven by differences in the osmotic pressure inside and outside of the cell and is influenced by cell wall properties. Legume leaf movements result from reversible deformation of pulvinar motor cells. Reversible cell deformation is an elastic process distinct from the irreversible cell growth of developing organs. Here, we begin with a review of the basic mathematics of cell volume changes, cell wall function, and the mechanics of bending deformation at a macro scale. Next, we summarize the findings of recent molecular genetic studies of pulvinar development. We then review the mechanisms of the adaxial/abaxial patterning because pulvinar bending deformation depends on the differences in mechanical properties and physiological responses of motor cells on the adaxial versus abaxial sides of the pulvinus. Intriguingly, pulvini simultaneously encompass morphological symmetry and functional asymmetry along the adaxial/abaxial axis. This review provides an introduction to leaf movement and reversible deformation from the perspective of mechanics and molecular genetics. [ABSTRACT FROM AUTHOR]

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Research on new conservation treatments for historical wood requires considerable amounts of appropriate wood material, which is hard to acquire. Thus, we produced biologically and chemically degraded model wood that could be used as a representative material in future research on consolidating agents. Using chemical composition determinations, we found that fungal decay targeted mainly polysaccharides, while alkaline treatment mostly reduced hemicelluloses and lignin content. X-ray and neutron scattering showed that all decayed samples had increased disorder in microfibril alignment and larger elementary fibril cross-sections, and alkaline-treated samples had much larger elementary fibril spacing compared to those decayed by fungi. These nanoscale and chemical differences correlate with physical property changes. For example, decreased cellulose crystallinity and increased disorder of the microfibrils in degraded cell walls likely contribute to the lower elastic moduli measured for these cell walls. The obtained data improves understanding of how degradation alters wood structures and properties across length scales and will be valuable for future studies focusing on archeological wood. Moreover, it leads to the conclusion that it is more appropriate to develop treatments that consider not only spatial variability and degree of wood degradation but also the corresponding molecular and nanoscale changes in the cell walls. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal treatment can improve the dimensional stability of wood, but it also decreases wood's toughness, or increases its brittleness. In this paper, combining FTIR spectroscopy and mechanical analysis were used to monitor wood molecular straining and deepen the micromechanical understanding of thermally-treated wood. The degradation of hemicellulose increased as the thermal treatment temperature increase, and the 220 °C treatment also led to cellulose microfibrils reorientation. The results of static tension FTIR spectra of thermally-treated wood indicated that the absorption peak of cellulose glycosidic bond underwent a substantial bandshift to lower wave numbers as the tensile strain increase, but the characteristic peak position of the lignin was no obvious change during stretching. For the 160–200 °C treated samples, the bandshift ratios of cellulose C–O–C glycosidic bond increased upon increasing the temperature; Furthermore, the intensities of the two split peaks of cellulose at 1169 cm−1 and 1435 cm−1 in 0° polarization dynamic FTIR spectra decreased upon increasing the treatment temperature, indicating the elastic-like response of cellulose for thermally-treated wood decrease. For the 220 °C treated sample, the bandshift ratio of cellulose glycosidic bond decreased compared with other thermal treatment samples, but the intensities of the two split peaks of cellulose increased again. Those results indicated that the shear slipping between cellulose microfibrils decrease and microfibrils reorientation due to hemicellulose degradation after thermal treatment may cause the toughness of the thermally-treated wood decrease, or the brittleness increase. [ABSTRACT FROM AUTHOR]

Wood is complex in its chemical composition that has an important influence on its chemical behavior and mechanical strength. The complexity is reflected in the ultrastructure of the wood cell wall. In particular, the concentration of main components (cellulose, hemicelluloses and lignin) changes depending on many factors such as the different type or parts of wood, and varies in different cell wall layers. From an ultrastructural standpoint, we describe the current level of knowledge about chemical characteristics of the wood cell walls. The information of distribution of main components in the cell walls of normal wood, reaction wood and water-logged archaeological wood, the cellulose microfibrils orientation, and the interactions between main components were presented based on the use of advanced techniques including transmission electron microscopy, scanning electron microscopy, spectral imaging and nuclear magnetic resonance. In addition, the chemical changes of the wood cell wall during pretreatment are discussed. This mini-review not only provides a better understanding of wood chemistry, but also brings new insights into cell wall recalcitrance. [ABSTRACT FROM AUTHOR]

Cellulose is the most abundant polysaccharide produced by plants. In the form of rigid microfibrils surrounding the cells, cellulose constitutes the load-bearing cell wall element that controls cell growth and shape. Cellulose microfibrils are laid down outside the cell by the multimeric plasma membrane-inserted cellulose synthase complexes (CSCs), which move along underlying cortical microtubules (CMTs). In plants, CSCs are shaped as rosettes with six lobes symmetrically arranged in a hexagonal structure. In Arabidopsis, the CSC is composed of at least three functionally non-redundant cellulose synthase (CESA) glycosyltransferases in both primary and secondary cell walls. The number, organization, and interactions of CESA proteins within the CSC have been debated for many years on the basis of numerous lines of evidence provided by electron microscopy, biochemical and genetic approaches, spectroscopic techniques, as well as computational modeling. The Arabidopsis thaliana model was extremely useful in elucidating the molecular composition of CSC and enabled to elucidate the specialized functions of distinct AtCESA isoforms. Several additional, non-CESA proteins involved in cellulose synthesis and its regulation were also identified in Arabidopsis. This review outlines the latest findings on CSC organization, trafficking, and plant-specific proteins directly associated with the complex and interconnecting CESAs with CMTs.

Wild oat (Avena sterilis) is a very common annual plant species. Successful seed dispersion support its wide distribution in Africa, Asia and Europe. The seed dispersal units are made of two elongated stiff awns that are attached to a pointy compartment containing two seeds. The awns bend and twist with changes in humidity, pushing the seeds along and into the soil. The present work reveals the material structure of the awns, and models their functionality as two-link robotic arms. Based on nano-to-micro structure analyses the bending and twisting hygroscopic movements are explained. The coordinated movements of two sister awns attached to one dispersal unit were followed. Our work shows that sister awns intersect typically twice every wetting-drying cycle. Once the awns cross each other, epidermal silica hairs are suggested to lock subsequent movements, resulting in stress accumulation. Sudden release of the interlocked awns induces jumps of the dispersal unit and changes in its movement direction. Our findings propose a new role to epidermis silica hairs and a new facet of wild oat seed dispersion. Reversible jumping mechanism in multiple-awn seed dispersal units may serve as a blueprint for reversibly jumping robotic systems. The seed dispersal unit of wild oats carries two elongated stiff awns covered by unidirectional silica hairs. The awns bend and twist with changes in humidity, pushing the seed capsule along and into the ground. We studied structures constructing the movement mechanism and modeled the awn as a two-link robotic arm. We show that sister awns, attached to the same seed capsule, intersect twice every drying cycle. Once the awns cross each other, the epidermal silica hairs are suggested to lock any subsequent movements, causing stress accumulation. Sudden release of the interlocked awns may cause the dispersal unit to jump and change its direction. Our findings suggest a new role to silica hairs and a new dispersal mechanism in multiple-awn seed dispersal units. [Display omitted] [ABSTRACT FROM AUTHOR]

A recent paper by Chan and Coen (March, 2020) proposes a dual mechanism hypothesis for the orientation of cellulose microfibrils in plant cell walls. One of these is an autonomous mechanism, which takes place outside the plasma membrane, within the cell wall itself (a). The other is the more complex microtubule-guided cellulose alignment process, where the orientation of microfibrils is directed by microtubules within the cell, via trans-membrane protein complexes (rosettes) (b). This mechanism can override the autonomous process and, it is argued, can explain how the production of complex detailed multi-layer alignment patterns of secondary walls is orchestrated. This paper concerns the latter process. It pushes the model one stage further back, by proposing a mechanism for the initial alignment of microtubules, in terms of the liquid crystalline state of the cortex. Justification for the hypothesis is given in terms of the in-vitro observations of the liquid crystalline mesophase formed by microtubules, and of the self-ordering properties of liquid crystalline systems in general. As an example, the production of a plant cell wall with a helicoidal array of cellulose microfibrils is pictured in some detail. [ABSTRACT FROM AUTHOR]

Plant cell deformation is a mechanical process that is driven by differences in the osmotic pressure inside and outside of the cell and is influenced by cell wall properties. Legume leaf movements result from reversible deformation of pulvinar motor cells. Reversible cell deformation is an elastic process distinct from the irreversible cell growth of developing organs. Here, we begin with a review of the basic mathematics of cell volume changes, cell wall function, and the mechanics of bending deformation at a macro scale. Next, we summarize the findings of recent molecular genetic studies of pulvinar development. We then review the mechanisms of the adaxial/abaxial patterning because pulvinar bending deformation depends on the differences in mechanical properties and physiological responses of motor cells on the adaxial versus abaxial sides of the pulvinus. Intriguingly, pulvini simultaneously encompass morphological symmetry and functional asymmetry along the adaxial/abaxial axis. This review provides an introduction to leaf movement and reversible deformation from the perspective of mechanics and molecular genetics.

A modified TEMPO-catalyzed oxidation of the solvent-exposed glucosyl units of cellulose to uronic acids, followed by carboxyl reduction with NaBD4 to 6-deutero- and 6,6-dideuteroglucosyl units, provided a robust method for determining relative proportions of disordered amorphous, ordered surface chains, and anhydrous core-crystalline residues of cellulose microfibrils inaccessible to TEMPO. Both glucosyl residues of cellobiose units, digested from amorphous chains of cellulose with a combination of cellulase and cellobiohydrolase, were deuterated, whereas those from anhydrous chains were undeuterated. By contrast, solvent-exposed and anhydrous residues alternate in surface chains, so only one of the two residues of cellobiosyl units was labeled. Although current estimates indicate that each cellulose microfibril comprises only 18 to 24 (1 → 4)-β-d-glucan chains, we show here that microfibrils of walls of Arabidopsis leaves and maize coleoptiles, and those of secondary wall cellulose of cotton fibers and poplar wood, bundle into much larger macrofibrils, with 67 to 86% of the glucan chains in the anhydrous domain. These results indicate extensive bundling of microfibrils into macrofibrils occurs during both primary and secondary wall formation. We discuss how, beyond lignin, the degree of bundling into macrofibrils contributes an additional recalcitrance factor to lignocellulosic biomass for enzymatic or chemical catalytic conversion to biofuel substrates. [ABSTRACT FROM AUTHOR]

Exploding seed pods of the common weed Cardamine hirsuta have the remarkable ability to launch seeds far from the plant. The energy for this explosion comes from tension that builds up in the fruit valves. Above a critical threshold, the fruit fractures along its dehiscence zone and the two valves coil explosively, ejecting the seeds. A common mechanism to generate tension is drying, causing tissues to shrink. However, this does not happen in C. hirsuta fruit. Instead, tension is produced by active contraction of growing exocarp cells in the outer layer of the fruit valves. Exactly how growth causes the exocarp tissue to contract and generate pulling force is unknown. Here we show that the reorientation of microtubules in the exocarp cell cortex changes the orientation of cellulose microfibrils in the cell wall and the consequent cellular growth pattern. We used mechanical modeling to show how tension emerges through growth due to the highly anisotropic orientation of load-bearing cellulose microfibrils and their effect on cell shape. By explicitly defining the cell wall as multi-layered in our model, we discovered that a cross-lamellate pattern of cellulose microfibrils further enhances the developing tension in growing cells. Therefore, the interplay of cell wall properties with turgor-driven growth enables the fruit exocarp to generate sufficient tension to power explosive seed dispersal. [Display omitted] • Growth generates contractility and pulling force in the fruit exocarp • Switch in microtubule orientation underlies change in cellular growth patterns • Crossed pattern of cellulose microfibrils enhances contraction of growing cells • Multi-layered growth framework used to model cross-lamellate cell walls How growth—a stress relaxation process—produces tension in exploding seed pods is puzzling. Mosca et al. find that a specific pattern of cell expansion, regulated by microtubule-dependent cellulose deposition, leads to contractile tension. Growth also has an active role in increasing tension on cellulose fibers in a cross-lamellate cell wall. [ABSTRACT FROM AUTHOR]

In this study, cellulose microfibril (CMF) suspensions were imaged during pipe flow at consistencies of 0.4%, 1.0%, and 1.6% with optical coherence tomography (OCT) to obtain images of the structure and the local velocity of the suspension. The viscosities obtained by combining pressure loss measurement with the OCT velocity data showed typical shear thinning behavior and were in excellent agreement with viscosities obtained with ultrasound velocity profiling. The structural OCT images were used to calculate the radial and the axial floc sizes of the suspension. A fit of power law to the geometrical floc size–shear stress data gave the same power law index for all consistencies, suggesting that floc rupture dynamics is independent of consistency. The dependence of viscosity and floc size on shear stress was similar, indicating that the shear thinning behavior of CMF suspensions is closely related to the rupture dynamics of flocs. The results also showed that an apparent attenuation coefficient of the OCT signal can be used to determine the consistency of CMF suspensions. [ABSTRACT FROM AUTHOR]

Wood is complex in its chemical composition that has an important influence on its chemical behavior and mechanical strength. The complexity is reflected in the ultrastructure of the wood cell wall. In particular, the concentration of main components (cellulose, hemicelluloses and lignin) changes depending on many factors such as the different type or parts of wood, and varies in different cell wall layers. From an ultrastructural standpoint, we describe the current level of knowledge about chemical characteristics of the wood cell walls. The information of distribution of main components in the cell walls of normal wood, reaction wood and water-logged archaeological wood, the cellulose microfibrils orientation, and the interactions between main components were presented based on the use of advanced techniques including transmission electron microscopy, scanning electron microscopy, spectral imaging and nuclear magnetic resonance. In addition, the chemical changes of the wood cell wall during pretreatment are discussed. This mini-review not only provides a better understanding of wood chemistry, but also brings new insights into cell wall recalcitrance.

Cellulose, a polysaccharide of β (1–4) linked D-glucose units, is a cheap, eco-friendly and most abundant natural polymer on this planet. Among various cellulosic materials, cotton cellulose is readily available, lignin-free, FDA approved, and widely used in the medical field because of its higher degree of biocompatibility and non-cytotoxic nature. Though cotton cellulose showed essential material properties for scaffold design, the least priority had been given to this material. The present study aimed at exploring the fabrication of scaffold using cotton microfibers for bone tissue engineering application. The study also aimed at improving the mechanical, physio-chemical and osteogenic properties of the microfibrous scaffold by crosslinking with citric acid and further modified with gelatin. FTIR indicated some interactions between cellulose, citric acid and gelatin within the scaffolds, while XRD results demonstrated the crystalline nature of scaffolds. Porosity and swelling studies demonstrated that all scaffolds are hydrophilic and porous. The microporous interconnected network of scaffolds was confirmed by FESEM. FESEM micrographs and MTT assay confirmed that all scaffolds were nontoxic to MG 63. Based on findings, it was concluded that gelatin coated cotton cellulose microfibers crosslinked with citric acid scaffold would be a potential template for bone tissue engineering. [ABSTRACT FROM AUTHOR]

Cellulose aerogels with variable specific surface areas were prepared by freeze-drying cellulose microfibrillar suspensions dispersed in mixtures of water and tert-butyl alcohol (TBA). Varying the composition of solvent used for the suspensions and the origin and composition of the microfibrils allowed to extensively tune the specific surface area of these aerogels, with values ranging from 32 to 280 m2/g. Depending on the solvent mixture composition, these aerogels presented substantial morphological differences, attributed to the templating power of the various crystals obtained during the freezing of the solvent mixtures. The aerogels were hydrophobized with sebacoyl chloride in a gas-phase reaction operated under conditions of either full or partial derivatization of the accessible surface. For fully grafted specimens, a linear correlation could be established between the overall degree of substitution of the grafted samples and the specific surface area of the aerogels before grafting. From the slope of this correlation line, an average number of grafted molecules per surface area of approximately 3 molecules/nm² could be calculated. Atomic-scale models gave a plausible overview of the full surface coverage of the aerogel microfibrils in good agreement with the experimental data. Contact angle measurements confirmed the hydrophobicity of the grafted aerogels, as well as the presence of heterogeneities for the partially grafted samples. [ABSTRACT FROM AUTHOR]

While the raw material type and the production method of cellulose micro- and nanofibrils (CMNFs) strongly affect the absolute values of the rheological parameters of their aqueous suspensions, the dependence of these parameters on consistency, c, is found to be uniform. The consistency index and yield stress of CMNF suspensions follow generally the scaling laws K ∼ c 2.43 and τ y ∼ c 2.26 , respectively, and a decent approximation for flow index is n = 0.30 × c - 0.43 . The variability of reported scaling exponents of these materials is likely mainly due to experimental uncertainties and not so much due to fundamentally different rheology. It is suggested that the reason behind the apparently universal rheological behavior of CMNF suspensions is the strong entanglement of fibrils; the flow dynamics of typical CMNF suspensions is dominated by interactions between fibril flocs and not by interactions between individual fibrils. [ABSTRACT FROM AUTHOR]

Saharan aloe vera cactus leaves fibers (SACLFs) are a biodegradable and renewable agro textile fiber enriched with cellulose polysaccharides. The isolation of cellulose nanocrystals (CNCs) from SACLFs is an alternative approach to reinforcement for bio-composites applications. In this study, we show that standard chemical methods for the extraction of cellulose microfibrils and sulfuric acid hydrolysis (64 wt%) will result in usable CNCs. The resulting CNCs were characterized by XRD, FTIR, TGA and TEM. Fourier Transform Infrared Spectroscopy (FT-IR) confirms that the maximum amount of noncellulosic materials is removed from SACLFs. High yield content (32%) of CNCs is achieved by sulfuric acid hydrolysis and sonication process. It also enhances the crystalline size and crystallinity index of CNCs, which are confirmed by XRD. TEM analysis of CNCs shows a rod-like structure with diameter (10–14 nm), length (200–255 nm) and high aspect ratio of 18–20, which confers good reinforcing properties. These were tested in biodegradable agar film, whose tensile strength is increased by 27% when 5 wt% of CNCs from SACLFs was incorporated into the matrix. The SACLFs represent an interesting source of cellulosic reinforcing materials. [ABSTRACT FROM AUTHOR]

In the current study, a mixture of formic acid (FA), acetic acid (AA), and acetone was used, for the first time, as a ternary solvent system to dissolve poly(ɛ-caprolactone) (PCL). In addition, as a biomaterial reinforcement, various amounts of cellulose microfibrils (CMF) (1.5, 3, and 5 wt.%), extracted from rice husk, were added to PCL solution, and subsequently the prepared suspensions were individually electrospun. Adding acetone to FA/AA solvent system led to fabrication of uniform electrospun nanofibers with the average diameter of 178 ± 38 nm. Upon CMF incorporation, the mean electrospun fiber diameter was increased to 320 ± 132 nm at 5 wt.% CMF mostly due to the solution viscosity rise. In addition, scanning electron microscopy (SEM) confirmed wider diameter distribution in the presence of CMF. The electrospun fibers were also analyzed via wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) to study the supermolecular structure and thermal behavior of fibrous bionanocomposites, respectively. Both the characterizations positively affect the PCL crystallinity as a result of CMF incorporation. The DSC measurements showed the highest crystallinity (70.11%) at 1.5 wt.% CMF incorporation. The effect of CMF addition on the hydrophilicity of PCL was also investigated by contact angle measurement, where a decreasing trend in contact angle was observed upon CMF loading. Moreover, in vitro degradability of the bionanocomposite nonwoven mats was studied in PBS solution. The rate of degradation was enhanced in the presence of CMF. Moreover, tensile mechanical analysis was carried out and CMF inclusion had a reinforcing impact on electrospun PCL. The highest modulus (19.17 ± 0.8 MPa) and ultimate tensile strength (UTS) (4.45 ± 0.32 MPa) were achieved at 1.5 wt.% CMF addition to PCL. [ABSTRACT FROM AUTHOR]

The cellulose microfibril-precipitated calcium carbonate (CMF–PCC) composite filler has been studied in improving the printing and optical properties of ordinary paper. However, the effect of CMF–PCC composite filler on the properties of Xuan paper, especially the ink diffusion properties, has rarely been investigated. In this study, the CMF–PCC composite filler was prepared by double-exchange reaction. The effects of CMF–PCC composite filler on the physical properties and ink diffusion properties of Xuan paper were detailedly studied. The results showed that the PCC particles in the CMF–PCC composite filler were rhombohedral calcite, with a uniform particle size and high adhesion rate, under the optimum reaction conditions. The Xuan paper filled with the CMF–PCC composite filler had higher tensile strengths and opacity than the conventional PCC or GCC loading. Notably, the CMF–PCC composite filler can effectively improve and regulate the Chinese ink diffusion properties of Xuan paper. [ABSTRACT FROM AUTHOR]

Cellulose is the most abundant polysaccharide produced by plants. In the form of rigid microfibrils surrounding the cells, cellulose constitutes the load-bearing cell wall element that controls cell growth and shape. Cellulose microfibrils are laid down outside the cell by the multimeric plasma membrane-inserted cellulose synthase complexes (CSCs), which move along underlying cortical microtubules (CMTs). In plants, CSCs are shaped as rosettes with six lobes symmetrically arranged in a hexagonal structure. In Arabidopsis, the CSC is composed of at least three functionally non-redundant cellulose synthase (CESA) glycosyltransferases in both primary and secondary cell walls. The number, organization, and interactions of CESA proteins within the CSC have been debated for many years on the basis of numerous lines of evidence provided by electron microscopy, biochemical and genetic approaches, spectroscopic techniques, as well as computational modeling. The Arabidopsis thaliana model was extremely useful in elucidating the molecular composition of CSC and enabled to elucidate the specialized functions of distinct AtCESA isoforms. Several additional, non-CESA proteins involved in cellulose synthesis and its regulation were also identified in Arabidopsis. This review outlines the latest findings on CSC organization, trafficking, and plant-specific proteins directly associated with the complex and interconnecting CESAs with CMTs. [ABSTRACT FROM AUTHOR]

In this paper, lignocellulosic fibers and cellulose microfibrils (CMFs) were extracted from palmyra fruit peduncle waste and investigated as naturally derived cellulosic materials for their potential use as reinforcement materials in composite applications. The physicochemical, mechanical, and thermal properties of the extracted fiber were studied. Physical and morphological analysis results revealed an extracted fiber diameter of 82.5 μm with a very rough surface, providing excellent interfacial bonding performance with the polymer matrix. Chemical, mechanical, and thermal results showed that the fibers consist mainly of cellulose as their crystallized phase, with a cellulose content of 56.5 wt% and a tensile strength of 693.3 MPa, along with thermal stability up to 252 °C. The chemically extracted CMFs exhibit a short, rough-surfaced, cylindrical cellulose structure with a diameter range of 10–15 μm. These CMFs demonstrate excellent thermal stability, withstanding temperatures up to 330 °C. Furthermore, the formation of CMFs is evident from a substantial increase in the crystallinity index, which increased from 58.2 % in the raw fibers to 78.2 % in the CMFs. FT-IR analysis further confirms the successful removal of non-cellulosic materials through chlorine-free chemical treatments. These findings strongly support the potential use of extracted fibers and CMFs as reinforcement materials in polymers. [ABSTRACT FROM AUTHOR]

The plant cell wall is a dynamic network of several biopolymers and structural proteins including cellulose, pectin, hemicellulose and lignin. Cellulose is one of the main load bearing components of this complex, heterogeneous structure, and in this way, is an important regulator of cell wall growth and mechanics. Glucan chains of cellulose aggregate via hydrogen bonds and van der Waals forces to form long thread-like crystalline structures called cellulose microfibrils. The shape, size, and crystallinity of these microfibrils are important structural parameters that influence mechanical properties of the cell wall and these parameters are likely important determinants of cell wall digestibility for biofuel conversion. Cellulose–cellulose and cellulose-matrix interactions also contribute to the regulation of the mechanics and growth of the cell wall. As a consequence, much emphasis has been placed on extracting valuable structural details about cell wall components from several techniques, either individually or in combination, including diffraction/scattering, microscopy, and spectroscopy. In this review, we describe efforts to characterize the organization of cellulose in plant cell walls. X-ray scattering reveals the size and orientation of microfibrils; diffraction reveals unit lattice parameters and crystallinity. The presence of different cell wall components, their physical and chemical states, and their alignment and orientation have been identified by Infrared, Raman, Nuclear Magnetic Resonance, and Sum Frequency Generation spectroscopy. Direct visualization of cell wall components, their network-like structure, and interactions between different components has also been made possible through a host of microscopic imaging techniques including scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. This review highlights advantages and limitations of different analytical techniques for characterizing cellulose structure and its interaction with other wall polymers. We also delineate emerging opportunities for future developments of structural characterization tools and multi-modal analyses of cellulose and plant cell walls. Ultimately, elucidation of the structure of plant cell walls across multiple length scales will be imperative for establishing structure-property relationships to link cell wall structure to control of growth and mechanics.

Graphical abstract Abstract Cellulose microfibrils (CMFs) are an intensely studied soft matter system for applications in food and beverage products. CMF dispersions can contribute to products texture and stability through their ability to influence rheology and to reinforce structure of composites. Here we study CMFs dispersions from bacterial origin in the presence of hydrolyzed soy protein isolate (HSPI). Applying high energy density mechanical deagglomeration on CMF in the presence of dissolved HSPI leads to large differences in the microstructure of their aqueous dispersions. The CMF networks are becoming more homogenous as quantified by confocal scanning laser microscopy. By increasing the concentration of CMF, at constant HSPI concentration, we observed a transition from a liquid like to a soft solid like behavior. The elastic properties in all cases are dominated by CMFs. CMF-HSPI hybrid material displays highly tunable mechanical properties which can find applications in texture control of food products. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Oil-in-water Pickering emulsions at high volume fractions (50 wt % oil) are prepared using cellulose microfibrils (CMF) from plant cell wall materials as emulsifiers and stabilizer. Confocal microscopy is used to monitor the changing CMF network over time and the rate of oil droplet coalescence. Without addition of glycerol the drying emulsion quickly coalesces, and a significant oil separation ensues. The rate of coalescence and the percentage of coalescence droplets and oil separation decrease as the concentration of CMF is increased. Addition of glycerol into the emulsions decreases the extent of droplet coalescence and oil separation. At 10 wt% added glycerol, coalescence could not be prevented but oil separation is minimal: the oil is mainly contained into honeycomb shaped cells made of CMF and glycerol. The results demonstrate the influence of the aqueous phase on the coalescence and film forming properties of CMF stabilized Pickering emulsions. [ABSTRACT FROM AUTHOR]

The present work describes the production of novel highly hydrated cellulose microfibrils (CMFs) with unique morphology from coffee pulp waste using specific chemical treatments. The as-produced CMFs were successfully characterized and then used as an adsorbent for removal of methylene blue (MB) from concentrated aqueous solutions. Surprisingly, it was found that the novel CMFs display high water-uptake ability, with a maximum swelling ratio of 265%, and that they form an entangled hydrated network gel in water. The morphological observation and nitrogen adsorption measurement demonstrated that the extracted CMFs exhibit an average fibril diameter of 11.5 µm and mesoporous structure with an average pore size of 6.37 nm. These special features make the as-produced CMFs excellent candidates to be used as adsorbents for removal of MB from concentrated solutions. The performed adsorption studies determined that the adsorption equilibrium was reached within 90 min. The adsorption kinetics data were well fitted to the pseudo-second-order kinetic model, and the adsorption isotherms were well described by the Freundlich isotherm model. In addition, the maximum adsorption capacity was 182.5 mg/g, much higher than that determined for other previously reported cellulose-based adsorbents. Through this study, we have demonstrated a possible strategy to give an added value to the coffee pulp waste, a by-product of the coffee processing industry, which is rich in cellulose, inexpensive and renewable source. Indeed, the extracted CMFs are very attractive for developing a sustainable and economically viable bio-sourced material for future growth of cellulose use in advanced applications. [ABSTRACT FROM AUTHOR]