Cellulose Crystals Research Articles

Enzymatic synthesis of cellulose in space: gravity is a crucial factor for building cellulose II gel structure

We previously reported in vitro synthesis of highly ordered crystalline cellulose II by reverse reaction of cellodextrin phosphorylase from the cellulolytic bacterium Clostridium (Hungateiclostridium) thermocellum (CtCDP), but the formation mechanism of the cellulose crystals and highly ordered structure has long been unclear. Considering the specific density of cellulose versus water, the formation of crystalline and highly ordered structure in an aqueous solution should be affected by gravity. Thus, we synthesized cellulose with CtCDP stable variant at the International Space Station, where sedimentation and convection due to gravity are negligible. Optical microscopic observation suggested that cellulose in space has a gel-like appearance without apparent aggregation, in contrast to cellulose synthesized on the ground. Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) indicated that cellulose synthesized in space has a more uniform particle distribution in the ~ 100 nm scale region than cellulose synthesized on the ground. Scanning electron microscopy (SEM) showed that both celluloses have a micrometer scale network structure, whereas a fine fiber network was constructed only under microgravity. These results indicate that gravity plays a role in cellulose II crystal sedimentation and the building of network structure, and synthesis in space could play a role in designing unique materials.Graphical abstract

A scientific approach for evaluating extremely caked paper manuscript kept in Al-Azhar Library in Cairo

PurposePaper aims to determinate caking paper manuscript cause through studying of the manuscript components, bio-deterioration and physio-chemical deterioration factor. It will facilitate manuscripts and paper conservators to understand paper blocking and caking phenomenon.Design/methodology/approachThe manuscript condition has been diagnosed by focusing on adhesion and fossilization regions. To achieve this, some methods of analysis and examination were used, such as visual examination, digital microscopy and scanning electron microscope were used to studying surface changes. X-ray diffraction and Fourier transform infrared microscopy were used to determinate of cellulose crystallinity, ink composition and identify the binding medium.FindingsThe results revealed the use of cotton pulp, and calcium carbonate was among the fillers that were used to improve the properties of paper. The crystallization of cellulose was lower in the first and last papers than the papers located in the heart of the manuscript. The most important reasons that led to the papers caking was the presence of fungi A. niger, Cladosporium sp, Chaetomium sp, by secreting some enzymes in combination with some other factors such as difference variation in temperature and moisture.Originality/valueAll deterioration factors participate with each other until rule the damage circle of the papers because one factor alone cannot stick the papers. It was inferred from the examinations and analyzes that were conducted for the samples.

Cellulose dissolution and gelation in NaOH(aq) under controlled CO2 atmosphere: supramolecular structure and flow properties.

We investigate the interplay between cellulose crystallization and aggregation with interfibrillar interactions, shear forces, and the local changes in the medium's acidity. The latter is affected by the CO2 chemisorbed from the surrounding atmosphere, which, combined with shear forces, explain cellulose gelation. Herein, rheology, nuclear magnetic resonance (NMR), small and wide-angle X-ray scattering (SAXS/WAXS), and focused ion beam scanning electron microscopy (FIB-SEM) are combined to unveil the fundamental factors that limit cellulose gelation and maximize its dissolution in NaOH(aq). The obtained solutions are then proposed for developing green and environmentally friendly cellulose-based materials.

Chiral Nematic Cellulose Nanocrystal Films Cooperated with Amino Acids for Tunable Optical Properties.

The exploration of functional materials relies greatly on the understanding of material structures and nanotechnologies. In the present work, chiral nematic cellulose nanocrystal (CNC) films were prepared by incorporation with four types of amino acids (AAs, glycine, histidine, phenylalanine, and serine) via evaporation-induced self-assembly. The films present ideal iridescence and birefringence that can be tuned by the amount of AAs added. The intercalation of AAs enlarged the pitch values, contributing to the red-shift trend of the reflective wavelength. Among the AAs, serine presented the most compatible intercalation into cellulose crystals. Interestingly, histidine and phenylalanine composite films showed high shielding capabilities of UV light in diverse wavelength regions, exhibiting multi-optical functions. The sustainable preparation of chiral nematic CNC films may provide new strategies for materials production from biocompatible lignocellulose.

Developing Edible Starch Film Used for Packaging Seasonings in Instant Noodles.

Edible starch-based film was developed for packaging seasoning applied in instant noodles. The edible film can quickly dissolve into hot water so that the seasoning bag can mix in the soup of instant noodles during preparation. To meet the specific requirements of the packaging, such as reasonable high tensile properties, ductility under arid conditions, and low gas permeability, hydroxypropyl cornstarch with various edible additives from food-grade ingredients were applied to enhance the functionality of starch film. In this work, xylose was used as a plasticizer, cellulose crystals were used as a reinforcing agent, and laver was used to decrease gas permeability. The microstructures, interface, and compatibility of various components and film performance were investigated using an optical microscope under polarized light, scanning electron microscope, gas permeability, and tensile testing. The relationship was established between processing methodologies, microstructures, and performances. The results showed that the developed starch-based film have a modulus of 960 MPa, tensile strength of 36 Mpa with 14% elongation, and water vapor permeability less than 5.8 g/m2.h under 20% RH condition at room temperature (25 °C), which meets the general requirements of the flavor bag packaging used in instant noodles.

Facile Post-Carboxymethylation of Cellulose Nanofiber Surfaces for Enhanced Water Dispersibility.

To improve the water dispersibility of cellulose nanofibers without deteriorating the physical properties, it is necessary to develop methods that can selectively modify fiber surfaces. Herein, the reaction conditions for carboxymethylation of the surface of nanofibrillated bacterial cellulose were optimized using chloroacetic acid as an etherification agent. Carboxymethylation in a high-concentration alkaline solution (>5 wt %) in the presence of isopropanol caused the mercerization and carboxymethylation of not only the nanofiber surface but also the cellulose crystals within the nanofiber, resulting in nanofiber swelling and an increase in fiber width. In contrast, with a dilute alkaline aqueous solution (3 wt %), the nanofiber surface was successfully carboxymethylated without changing the inner structure. Furthermore, the morphology was not affected by the carboxymethylation reaction, and no fiber swelling occurred under these reaction conditions. When the substitution reaction proceeded only on the nanofiber surface, the maximum degree of substitution (i.e., the average number of carboxymethyl groups substituted per anhydroglucose residue in cellulose) was 0.091. After surface modification, the nanofibers became more negatively charged, which improved the dispersibility in water through electrostatic repulsion, resulting in a drastic increase in the transparency of the nanofiber dispersion. This method provides a general approach for the surface modification of cellulose nanofibers to increase water dispersibility.

Hybrid fibroin-nanocellulose composites for the consolidation of aged and historical silk

Silk artifacts are a valuable artistic and historical heritage, but are prone to degradation that makes the fibers fragile, hindering the preservation of precious collections. Dispersions of self-regenerated silk fibroin (SRSF) can be used to cast films on aged fibers and recover their mechanical properties, but there appears to be a limit to the fibroin concentration in the dispersions, as too concentrated systems produce highly crystalline but mechanically brittle films. Alternatively, we propose here hybrid dispersions of SRSF and cellulose nanocrystals (CNC) with the aim to grant the aged fibers improved strength, taking advantage of the SRSF structuration induced by CNC, and of the intrinsic mechanical properties of the cellulose crystals. We demonstrate that CNC speeds up the assembly of fibroin in the hybrid dispersions, leading to the formation of more compact colloidal structures at the nanoscale than the sole SRSF. When the hybrid dispersions film, the presence of CNC favors the formation of crystalline structures (most notably α-helices) even at low fibroin concentration, and the films confer optimal axial strength to aged silk fibers, surpassing the performance of single-component (SRSF or CNC) dispersions at the same concentration of consolidant, and of pure crystalline SRSF. Overall, the hybrid formulations candidate as new sustainable tools for the preservation of historical textiles, employing renewable materials (cellulose and silk scraps) to restore artifacts.

Influence of torrefaction on the heating values and energy densities of hardwood and softwood

Lumber manufacturing facilities generate large amounts of wood residues as a by-product of processing. In this study, the torrefaction characteristics of the Cryptomeria japonica and Acacia confusa residues were evaluated and compared to microcrystalline cellulose. The torrefied products also were analyzed. The results showed that the higher heating value (HHV) of the C. japonica and A. confusa residues increased to 5,993 and 5,576 kcal/kg after 20 min of torrefaction at 310 °C, which was higher than the microcrystalline cellulose (4,340 kcal/kg). The energy densification of the torrefied biomass could rise to 1.17 to 1.20 times higher than the raw biomass. The condensable gaseous product was an organic acid liquid. The liquid product consisted of some alkanes, alcohols, esters, and amides. The exothermic temperature would be reduced after torrefaction. Additionally, the thermal treatment of the biomass destroyed the cellulose crystals and reduced the cellulose crystallinity index. In order to reduce the usage of fossil fuels, the torrefied solid biomass could be mixed with coal in power plants directly.

Pretreatment of corn cobs and corn stalks with tetrabutyl phosphate hydroxide ionic liquid to enhance enzymatic hydrolysis process

The abundant lignocellulosic biomass used to produce biofuels was considered the most promising alternative to fossil fuels. In view of this, many studies directly use ionic liquids (ILs) to pretreat lignocellulose for subsequent fermentation. Herein, the strong proton acceptor tetrabutyl phosphorus hydroxide (TBPH) aqueous solution was employed to pretreat corn cobs and corn stalks. The effects of pretreatment time (0.5–2 h), temperature (20–80 ℃), TBPH aqueous solution concentration (10–40 wt%) and liquid to solid ratio (4 wt/wt-9 wt/wt) on the components and sugar yield were investigated. For the pretreatment of corn cob and corn stalk, the sugar yield was 90.75% and 80.84%, which were about 4 and 4.6 folds of the raw materials (unpretreated corn cob: 22.5% and unpretreated corn stalk: 17.7%). Characterization results confirmed that the lignin and hemicellulose were significantly removed, and the cellulose crystals remained intact. Before and after pretreatment, the two raw materials changed from the initial dense surface morphology to porous and therefore contributed to enhancing the accessibility of cellulose during enzymatic hydrolysis. Furthermore, the sugar yield could still be maintained above 70% after the TBPH aqueous solution was reused 5 times. These results provide guidance for the conversion of other biomass to sugar and further fermentation to prepare the essential products.

Atherogenic index and lipid profiles in albino rats fed with surface modified Hibiscus sabdariffa cellulose

Despite the several applications of modified cellulose, there is limited information on their safety, and antidyslipidemic functions, which are the focus of this study. To address this, cellulose isolated from Hibiscus sabdariffa cellulose was surface modified using nitrilotriacetic acid to produce nitrilotriacetic acid modified Hibiscus sabdariffa cellulose (HSNT). It was characterized using Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TGA) analysis, scanning electron microscopy (SEM) and carbon, hydrogen, nitrogen, sulfur/oxygen (CHNS/O) analyzer. The study further investigated the safety of HSNT at the doses of 50, 100, and 150 mg kg−1 body weight in albino rats after a 7-day uninterrupted oral gavage. Histology of cardiac and hepatic tissues was observed, in addition to estimation of clinico-biochemical parameters such as atherogenic index of plasma (AIP), Castelli's risk index (CRI-1), total cholesterol, high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), albumin (ALB), aspartate aminotransferase (AST) and alanine aminotransferase (ALT). FTIR revealed peaks corresponding to the synthesis of HSNT, while XRD showed HSNT to have a crystallinity index of 53.20% with a type I cellulose crystal. HSNT had no significant effect on the absolute heart and liver weights, heart and liver organo-somatic indices, TG, AST, and ALB. Exposure to HSNT-50 caused a significant decrease in AIP levels. However, administration of HSNT-100 and 150 significantly reduced ALT, total cholesterol, and CRI-1 levels but caused a significant elevation in HDL-C levels. Cardiac histology revealed mild inflammatory and fatty infiltration of the myocardium, while the significant indications of the hepatic morphology included congestion of vessels and mild focal periportal infiltration at the HSNT-100 and HSNT-150 doses. Our preliminary data seem to indicate the potential of HSNT modification to resolve blood lipid abnormalities and make a case for an expanded study on its cardio-hepatic effects as well as study to understand the causes of congestion in hepatic vessels.

Off-axis photoelasticity by anisotropic molecular deformation of uniaxially aligned cellulose nanofiber films

We report the angle dependence of the photoelasticity for unidirectionally aligned films of bacterial cellulose nanofibers (CNFs) by applying the off-axis stress at 0°–90° with respect to the CNF orientation. The photoelastic coefficient was positive when the stress direction was close to the CNF axial direction, and it was negative when the stress was applied close to the lateral direction. The positive to negative photoelasticity was also observed in the off-axis photoelasticity of the cellophane film and in the density functional theory (DFT) calculations for the stretching between two atoms in the cellobiose model. On the other hand, unlike the cellophane film, the CNF film showed a positively and negatively asymmetric photoelasticity of 5 to −10 TPa−1, reflecting the anisotropy of the crystal modulus tensor. We found that the presence or absence of cellulose crystals controls the anisotropy of photoelasticity by constraining the molecular deformation.

Lignin enhances cellulose dissolution in cold alkali

Aqueous sodium hydroxide solutions are extensively used as solvents for lignin in kraft pulping. These are also appealing systems for cellulose dissolution due to their inexpensiveness, ease to recycle and low toxicity. Cellulose dissolution occurs in a narrow concentration region and at low temperatures. Dissolution is often incomplete but additives, such as zinc oxide or urea, have been found to significantly improve cellulose dissolution. In this work, lignin was explored as a possible beneficial additive for cellulose dissolution. Lignin was found to improve cellulose dissolution in cold alkali, extending the NaOH concentration range to lower values. The regenerated cellulose material from the NaOH-lignin solvents was found to have a lower crystallinity and crystallite size than the samples prepared in the neat NaOH and NaOH-urea solvents. Beneficial lignin-cellulose interactions in solution state appear to be preserved under coagulation and regeneration, reducing the tendency of crystallization of cellulose.

Effect of mechano-chemical pretreatment on valorizing plant waste for 5-hydroxymethylfurfural under microwave hydrothermal treatment

Plant waste (PW) is a common and abundant renewable biomass resource whose total amount is constantly increasing and accounts for up to 50% of municipal solid waste. This study aims to develop a valorization method for PW. A two-stage treatment method combining mechanical ball milling (BM) and microwave hydrothermal treatment (MHT) was investigated. BM can effectively destroy the crystallization of cellulose and reduce the particle size to increase the specific surface area and improve the MHT efficiency. The BM-MHT process could improve the 5-hydroxymethylfurfural (HMF), which is significantly higher than physical methods like grinding, ultrasonic and liquid nitrogen treatment. The BM conditions were further optimized by using a Box-Behnken Design with response surface methodology. The model showed that the highest HMF yield could reach 1.8% at 150 °C in MHT process after BM. An economic analysis indicated that BM-MHT offers a green treatment method with great economic benefits. It provides a novel valorization strategy for organic waste like PW.

Orientation of Cellulose Nanocrystals Controlled in Perpendicular Directions by Combined Shear Flow and Ultrasound Waves Studied by Small-Angle X-ray Scattering

The combined effect of shear flow and ultrasound (US) waves on the dynamical structural orientations of cellulosic cholesteric liquid crystals was investigated by time-resolved, in situ small-angle X-ray scattering (SAXS). A dedicated channel-type shear flow/ultrasound cell for SAXS characterization was developed to simultaneously generate a shear flow-induced horizontal stress force and a US-induced vertical acoustic radiation force. The control of the alignment of anisometric cellulose nanocrystals (CNCs), with their director parallel to the ultrasonic wave direction of propagation, was revealed at an unprecedented nanometer scale. Concurrently, the application of shear flow induced a horizontal orientation of CNCs with their directors aligned along the velocity direction. By adjusting the level of simultaneously applied shear flow and US intensity to the CNC suspensions, it was possible to tune the direction and the level of orientation of the CNCs during a period of time. For a specific ratio of the applied shear rate to acoustic power, some transient orientation of the CNCs at an intermediate angle between horizontal and vertical directions was evidenced. Relaxation of these orientations’ phenomena upon cessation of flow and/or US was also highlighted.

Factors Affecting the Catalytic Efficiency and Synergism of Xylanase and Cellulase During Enzymatic Hydrolysis of Birch Wood.

Understanding factors that affect the catalytic efficiency and synergism of enzymes is helpful to enhance the process of bioconversion. In this study, birch wood (BW) was sequentially treated by delignification (DL), deacetylation (DA), and decrystallization (DC) treatments. The physiochemical structures of treated BW were characterized. Moreover, the influences of sequential treatments on the catalytic efficiency and synergism of xylanase and cellulase were studied. DL treatments efficiently improved the conversion of cellulose and xylan. A high degree of synergy (DS) between xylanase and cellulase was produced during hydrolysis of DL-treated BW. DA treatments enhanced xylan conversion but reduced the DS between xylanase and cellulase for xylan hydrolysis, whereas DC treatments enhanced cellulose conversion but reduced the DS between xylanase and cellulase for cellulose hydrolysis. The cellulose conversion of lithium chloride/N,N-dimethylacetamide (LiCl/DMAc)-treated BW (89.69%) was higher than the cellulose conversion of ball milling (BM)-treated BW (81.63%), whereas the xylan conversion of LiCl/DMAc-treated BW (83.77%) was lower than the xylan conversion of BM-treated BW (87.21%). This study showed that the catalytic efficiency and synergism of xylanase and cellulase are markedly affected by lignin hindrance, hemicellulose acetylation, and cellulose crystallization.

Effect of oxidation on cellulose and water structure: a molecular dynamics simulation study

Enzymatic cleavage of glycocidic bonds is an important, green and biocompatible means to refine lignocellulosic biomass. Here, the effect of the resulting oxidation point defects on the structural and water interactions of crystalline cellulose {100} surface are explored using classical molecular dynamics simulations. We show that even single oxidations reduce the connections within cellulose crystal significantly, mostly via local interactions between the chains along the surface plane but also via the oxidation defects changing the structure of the crystal in direction perpendicular to the surface. Hydrogen bonding on the surface plane of cellulose is analyzed to identify onset of desorption of glucose chains, and the desorption probed. To assess the actual soluble product profile and their fractions resulting from lytic polysaccharide monooxygenase (LPMO) enzyme oxidation on real cellulose crystal samples, we employ High-Performance Anion-Exchange Chromatography with Pulsed Amperometric-Detection (HPAEC-PAD) technique. The findings demonstrate the LPMO oxidation results in soluble glucose fragments ranging from 2 to 8 glucose units in length. Additionally, significantly more oxidized oligosaccharides were released in LPMO treatment of AaltoCell than Avicel, the two studied microcrystalline cellulose species. This is likely to result from the large reactive surface area preserved in AaltoCell due to manufacturing process. Furthermore, as can be expected, the oxidation defects at the surfaces lead to the surfaces binding a larger amount of water both via direct influence by the defect but also the defect induced protrusions and fluctuations of the glucose chain. We quantify the enhancement of water interactions of cellulose crystals due to the oxidation defects, even when no desorption takes place. The molecular simulations indicate that the effect is most pronounced for the C1-acid oxidation (carboxylic acid formation) but present also for the other defects resulting from oxidation. The findings bear significance in understanding the effects of enzymatic oxidation on cellulose nanocrystals, the difference between cellulose species, and cleavage of soluble products from the cellulosic material.

Moisture induced straining of the cellulosic microfibril

Moisture absorption in the cell wall structure of wood is well known to induce considerable swelling of the wood exerting high expansion forces. This swelling is mainly induced by the sorptive action of the hydroxyl groups of the carbohydrate wood polymers; cellulose and hemicelluloses. On the ultrastructural level, there are, however, still questions with regard to the detailed deformations induced by this moisture absorption. Here, FTIR spectroscopy and synchrotron-radiation-based X-ray diffraction were used on paper samples to study the deformation of the cellulose crystals as a consequence of moisture absorption and desorption. Both techniques revealed that the moisture absorption resulted in a transverse contraction of the cellulose crystals accompanied by a somewhat smaller elongation in the cellulose chain direction. The deformations were found to be a direct response to the increased moisture content and were also found to be reversible during moisture desorption. It is hypothesised that these deformations are a consequence of the swelling forces created by the combined longitudinal and lateral expansions of the non-crystalline cellulose molecules and the glucomannan hemicellulose aligned along the cellulose crystals. These forces will impose a lateral contraction of the cellulose crystals, as well as a longitudinal extension of it.Graphic abstract

Conductive Cellulose Bio‐Nanosheets Assembled Biostable Hydrogel for Reliable Bioelectronics

AbstractBiostable electronic materials that can maintain their super mechanical and conductive properties, even when exposed to biofluids, are the fundamental basis for designing reliable bioelectronic devices. Herein, cellulose‐derived conductive 2D bio‐nanosheets as electronic base materials are developed and assembled into a conductive hydrogel with ultra‐high biostability, capable of surviving in harsh physiological environments. The bio‐nanosheets are synthesized by guiding the in situ regeneration of cellulose crystal into a 2D planar structure using the polydopamine‐reduced‐graphene oxide as supporting templates. The nanosheet‐assembled hydrogel exhibits stable electrical and mechanical performances after undergoing aqueous immersion and in vivo implantation. Thus, the hydrogel‐based bioelectronic devices are able to conformally integrate with the human body and stably record electrophysiological signals. Owing to its tissue affinity, the hydrogel further serves as an “E‐skin,” which employs electrotherapy to aid in the faster healing of chronic wounds in diabetic mice through transcutaneous electrical stimulation. The nanosheet‐assembled biostable, conductive, flexible, and cell/tissue affinitive hydrogel lays a foundation for designing electronically and mechanically reliable bioelectronic devices.

The colloidal structure of a cellulose fiber

We present a small angle X-ray scattering (SAXS) study of the colloidal structure of regenerated cellulose fibers, air-gap spun from an ionic liquid solution. Based on the data, and a different interpretation of the anisotropic SAXS pattern, we propose a slightly different colloidal structure of the fibers, than what is commonly assumed for regenerated cellulose fibers. Fibers with two different degrees of orientation, as produced by different draw ratios, DR = 2 and 15, respectively, are analyzed. The 2D SAXS pattern is highly anisotropic with striking cross-like pattern, having scattering predominantly perpendicular and parallel to the fiber axis. This cross-like pattern suggest a colloidal structure with oriented crystalline lamellae of ca. 10 nm thickness, embedded within a continuous matrix of amorphous cellulose. The lamellae are oriented with their normal parallel with the fiber axis. Complementary wide angle X-ray diffraction data confirm that the lamellae normal direction corresponds to the cellulose chain direction (c-direction) in the monoclinic cellulose crystal (Cellulose II).Graphic abstract

Cell wall configuration and ultrastructure of cellulose crystals in green seaweeds

Green seaweeds (Chlorophyta) are often considered a nuisance, but may in fact constitute a potential climate-friendly renewable resource in the new bioeconomy. Utilization of green seaweed polysaccharides could in particular enable a new type of green growth in coastal regions in developing countries e.g. in West Africa. The carbohydrate constituents, including cellulose, are lignin-free, but only limited knowledge is available on the cellulose ultrastructure and cellulose crystallinity in commonly occurring green seaweeds. Abundantly available green seaweeds along the coast in West Africa include Chaetomorpha linum, Caulerpa taxifolia, Ulva fasciata and Ulva flexuosa. Here, using X-ray diffraction (XRD), on cellulose gently purified from the green seaweeds, we determined that mainly cellulose Iα was present in both C. linum and U. flexuosa. We also found that the crystallite diameter was particularly large, 16 nm, in both the Ghanaian and the Danish C. linum samples, especially compared to the crystallite diameter of 2.5–5 nm in most terrestrial vascular plants (Tracheophytes), which mainly contain cellulose Iβ. For U. flexuosa, increasing crystallinity of the cellulose was achieved during purification. Cellulose purification was not achievable for C. taxifolia, indicating that in this species the glucose is mainly a constituent of other carbohydrates, presumably notably of starch. Transmission electron microscopy (TEM) confirmed the large size of the crystallites of C. linum showing the cellulose forming a multi-lamellar structure with alternating perpendicular and parallel layers along the fibre axis. The cell wall nano-structure appeared amorphous in C. taxifolia and as a network in U. fasciata and U. flexuosa. As glucose was most abundant in C. linum and its cellulose was crystalline, this green seaweed species appears particularly promising as a source for manufacturing of novel cellulose-based materials, e.g. specialized paper or cellulose-based composite materials.