Cellulose Microcrystals Research Articles

Dynamics of Cellulose Whiskers in Agarose Gels. 1. Polarized Dynamic Light Scattering

The dynamics of cotton cellulose microcrystals (“whiskers”) trapped in agarose hydrogels of varying concentrations was studied by polarized dynamic light scattering. The rigid agarose network strongly heterodynes the signal of the mobile whiskers, thereby enabling the measurement of their diffusion coefficient D and their fluctuating scattered intensity Rθ. For low agarose gel concentrations, i.e., when the mesh size of the agarose network is larger than the length of the whiskers, the dynamics does not depend on the whisker content. The product of D and Rθ, which is inversely proportional to the friction coefficient, is independent of the gel concentration, indicating that the network does not hinder the whiskers. When the mesh size of the network is smaller than the length of the whiskers, the whisker content influences the dynamics and the product RθD becomes dependent on the gel concentration; i.e., frictional effects arise. Also in this condition domains with different whisker contents may develop in the gel.

Improved Structural Data of Cellulose IIII Prepared in Supercritical Ammonia

Highly crystalline cellulose IIII samples were prepared by subjecting oriented films consisting of an assembly of Cladophora cellulose microcrystals to supercritical ammonia. Diffraction data recorded on these specimens indicated that the crystals of cellulose IIII could be fully described with a one-chain unit cell and a P21 space group, with the cellulose chain axis on one of the 21 screw axes of the cells. The new cell had the following parameters: a = 0.448 nm, b = 0.785 nm, c (chain axis) = 1.031 nm, γ = 105.1°. In this cell, which is half of the one proposed so far for cellulose IIII, one glucosyl residue becomes the asymmetric unit. A good agreement between the diffraction analysis and spectroscopic data was observed. 13C CP/MAS spectra of the samples presented only six sharp resonance peaks, attributed to the six carbons of the asymmetric glucosyl residue. In these spectra, the occurrence of the C6 signal at 62.3 ppm is a clear indication that the hydroxymethyl moiety is in the gt conformation. F...

Preparation of Activated Carbon Pellets without Binder and Their Methane Adsorption Propertie

Activated carbon pellets were prepared from cellulose microcrystals without binder. The column form of activated carbon pellets was maintained after heat treatment by use of compressed cellulose microcrystals. The bulk density of the activated carbon pellets increased with increasing compression pressure of the raw materials. On the other hand the total pore volume decreased.The bulk density of the activated carbon pellets is 2.5 times greater than that of activated carbon powder under the same sintering conditions. The amount of methane adsorption at 30°C is 82 mg/g at 0.86MPa. The total methane storage efficiency of adsorbed gas is 280 cm3 in 1 cm3 volume of the activated carbon pellet prepared in this work, being 1.7 times higher than that of the methane compressed at 13.0 MPa.

Localization of Iα and Iβ phases in algal cellulose revealed by acid treatments

Highly crystalline Iα-rich type Cladophora cellulose, which had been kept in never-dried condition, was treated in 60wt% sulfuric acid at 100°C, for 1–48h. The cellulose microcrystals thus obtained were analysed by X-ray diffractometry, FT-IR, and transmission electron microscopy. The Iα component was found to be more degraded than the Iβ component. The cellulose Iα/Iβ ratios of the samples acid-treated for 0, 24, and 48 h were about 8:2, 6:4, and 4:6, respectively. After the acid treatment, the microcrystals became narrower in width, and very sharp at their ends. These results indicate that the Iα phase is mostly located at the surface of the microcrystals, which is morphologically more susceptible to the acid treatment.

Steric Stabilization of a Cellulose Microcrystal Suspension by Poly(ethylene glycol) Grafting

A sterically stabilized aqueous suspension of rodlike cellulose microcrystals was prepared by the combination of acid hydrolysis of native cellulose, oxidative carboxylation of microcrystals, and grafting of poly(ethylene glycol) having a terminal amino group on one end (PEG-NH2, MW = 1000) using water-soluble carbodiimide. Chemical binding of PEG to the microcrystals was confirmed by weight increase, diminishment of carboxyl groups, thermogravimetry, and infrared spectroscopy, resulting in consumption of 20−30% of the initially introduced carboxyl groups. The amount of bound PEG was 0.2−0.3 g/g of cellulose. The PEG-grafted cellulose microcrystals showed drastically enhanced dispersion stability, that is, resistance to addition of 2 M sodium chloride, and ability to redisperse into either water or chloroform from the freeze-dried state. The concentrated aqueous suspension of PEG-grafted microcrystals formed a chiral nematic mesophase through a phase separation similar to that of the ungrafted sample, but with a reduced spacing of the fingerprint pattern.

Nonflocculating and Chiral-Nematic Self-ordering of Cellulose Microcrystals Suspensions in Nonpolar Solvents

Nonflocculating and Chiral-Nematic Self-ordering of Cellulose Microcrystals Suspensions in Nonpolar Solvents

Imaging the enzymatic digestion of bacterial cellulose ribbons reveals the endo character of the cellobiohydrolase Cel6A from Humicola insolens and its mode of synergy with cellobiohydrolase Cel7A.

Dispersed cellulose ribbons from bacterial cellulose were subjected to digestion with cloned Cel7A (cellobiohydrolase [CBH] I) and Cel6A (CBH II) from Humicola insolens either alone or in a mixture and in the presence of an excess of beta-glucosidase. Both Cel7A and Cel6A were effective in partially converting the ribbons into soluble sugars, Cel7A being more active than Cel6A. In combination, these enzymes showed substantial synergy culminating with a molar ratio of approximately two-thirds Cel6A and one-third Cel7A. Ultrastructural transmission electron microscopy (TEM) observations indicated that Cel7A induced a thinning of the cellulose ribbons, whereas Cel6A cut the ribbons into shorter elements, indicating an endo type of action. These observations, together with the examination of the digestion kinetics, indicate that Cel6A can be classified as an endo-processive enzyme, whereas Cel7A is essentially a processive enzyme. Thus, the synergy resulting from the mixing of Cel6A and Cel7A can be explained by the partial endo character of Cel6A. A preparation of bacterial cellulose ribbons appears to be an appropriate substrate, superior to Valonia or bacterial cellulose microcrystals, to visualize directly by TEM the endo-processivity of an enzyme such as Cel6A.

Birefringent Glassy Phase of a Cellulose Microcrystal Suspension

We prepared a stable and highly viscous suspension of cellulose microcrystals by postsulfating the HCl-hydrolyzed cellulose microcrystals. The neutralized suspension was isotropic and showed flow birefringence at low solid content (ca. <1%). At a solid content of approximately 2−3%, the suspension was still flowing but showed intricate birefringent patterns, which remained after the flow had ceased. At high solid content (7.1%), the suspension became too viscous to flow and showed a frozen-in birefringent pattern with a microscopic crosshatch texture. These features show that this postsulfated suspension forms a “birefringent glassy phase”, similar to that observed for a boehmite rod suspension, being distinctly different from the behavior of the suspension prepared by direct hydrolysis of cellulose with concentrated sulfuric acid.

Shear-Induced Orientation Phenomena in Suspensions of Cellulose Microcrystals, Revealed by Small Angle X-ray Scattering

The alignment of cellulose microcrystals in a 6.9% (w/w) colloidal aqueous suspension under shear was characterized using small angle synchrotron radiation scattering. Prior to shearing, the microcrystals appeared randomly oriented and went through a two-step alignment process with increasing shear rate. At shear rates lower than 5 s-1, the X-ray scattering patterns indicated little or no preferential alignment in the shear direction; however, in the plane perpendicular to the shear direction, the microcrystals were preferentially oriented in the vertical direction. At shear rates of 5 s-1 and higher, the microcrystals were aligned horizontally along the shear direction. These orientation phenomena were found to be dependent on shear rate and completely reversible. They are likely due to the presence of planar domains of randomly oriented microcrystals which align at low shear rates and are broken up at higher shear rates enabling alignment of the individual microcyrstals.

Digestion of crystalline cellulose substrates by the Clostridium thermocellum cellulosome: structural and morphological aspects

The action of cellulosomes from Clostridium thermocellum on model cellulose microfibrils from Acetobacter xylinum and cellulose microcrystals from Valonia ventricosa was investigated. The biodegradation of these substrates was followed by transmission electron microscopy, Fourier-transform IR spectroscopy and X-ray diffraction analysis, as a function of the extent of degradation. The cellulosomes were very effective in catalysing the complete digestion of bacterial cellulose, but the total degradation of Valonia microcrystals was achieved more slowly. Ultrastructural observations during the digestion process suggested that the rapid degradation of bacterial cellulose was the result of a very efficient synergistic action of the various enzymic components that are attached to the scaffolding protein of the cellulosomes. The degraded Valonia sample assumed various shapes, ranging from thinned-down microcrystals to crystals where one end was pointed and the other intact. This complexity may be correlated with the multi-enzyme content of the cellulosomes and possibly to a diversity of the cellulosome composition within a given batch. Another aspect of the digestion of model celluloses by cellulosomes is the relative invariability of their crystallinity, together with their Ialpha/Ibeta composition throughout the degradation process. Comparison of the action of cellulosomes with that of fungal enzymes indicated that the degradation of cellulose crystals by cellulosomes occurred with only limited levels of processivity, in contrast with the observations reported for fungal enzymes. The findings were consistent with a mechanism whereby initial attack by a cellulosome of an individual cellulose crystal results in its 'commitment' towards complete degradation.

Flow properties of microcrystalline cellulose suspension prepared by acid treatment of native cellulose

The properties of cellulose microcrystals and their colloidal suspensions obtained by acid treatments of native cellulose have been investigated. Bleached softwood kraft pulp was treated with 65% (w/w) sulfuric acid or 4 N hydrochloric acid and the resulting particle morphology and flow properties of the aqueous suspensions were studied. Colloidal dispersion of the HCl-treated sample was obtained by more thorough removal of acid from the hydrolysate than in the case of H 2SO 4 treatment. The H 2SO 4-treated and HCl-treated samples had similar particle sizes and shapes when observed by electron microscopy. Conductometric titration of suspensions revealed that the H 2SO 4-treated sample had a surface charge of 84 m-equiv kg −1 dry material due to the introduction of sulfate groups, while that of the HCl-treated sample was undetectable. The H 2SO 4-treated suspension showed no time dependence in viscosity, while the HCl-treated suspension was thixotropic at concentrations >0.5% (w/v) and anti-thixotropic <0.3%. The inclination of the relative viscosity–concentration plot (Einstein coefficient) for the H 2SO 4- and HCl-treated suspensions were 135 and 1380, respectively. The former value, when used in Simha's equation for rod-like particle suspension, roughly corresponds to an axis ratio of 50 estimated from the micrographs.

Unidirectional processive action of cellobiohydrolase Cel7A on Valonia cellulose microcrystals

On the basis of the `parallel-up' structure of the cellulose crystal, a crystallographic approach to study the mode of action of cellobiohydrolase Cel7A on Valonia cellulose microcrystal has been carried out. After incubation with Cel7A, most of the initially smooth and well defined Valonia microcrystals displayed fibrillation. However, as the hydrolysis reaction was rather heterogeneous, some microcrystals remained superficially intact. Close investigation on such crystals revealed polar morphology: one end was narrowed extremely or pointed. Electron microdiffraction analysis of these crystals evidenced that the narrowing of the microcrystals occurs at their reducing end side. This was also confirmed by the visualization of selective reducing end labeling at the pointed ends of microcrystals. These lines of investigation are the first demonstration that the processivity of Cel7A action against insoluble highly crystalline celluloses is unambiguously toward non-reducing ends from reducing ends.

Surface structure of native cellulose microcrystals by AFM

) and a monoclinic (Iβ) crystal form within the same microfibril; the main difference between them being a displacement of adjacent chains by a quarter of the c-axis period to give either a diagonally shifted or staggered arrangement of the cellobiose units. The most significant finding in this work is that it has been possible to image the cellobiose repeat along the chain because of topographic differences associated with the asymmetric glucose unit, and thus identify triclinic structure on the microcrystal surface. Computer modelling has been used to construct pseudo-AFM topography images from Connolly surfaces of the facets of the two different crystal forms, and the triclinic models are in excellent agreement with the real images obtained by AFM.

Surface structure of native cellulose microcrystals by AFM

Surface structure of native cellulose microcrystals by AFM

Thermoplastic nanocomposites filled with wheat straw cellulose whiskers. Part II: Effect of processing and modeling

AbstractThe reinforcing effect of cellulose microcrystals, or whiskers, dispersed in a thermoplastic matrix is analyzed. In Part I [Polym. Compos., 17, 604 (1996)], the preparation and the characterization of cellulose whiskers obtained from wheat straw were detailed. Composite films were processed by freeze‐drying and molding a mixture of aqueous suspension of these microcrystals and a film forming latex of poly(Styrene‐co‐ButylAcrylate). Using the same filler and latex, materials were processed by casting and evaporating the mixture of aqueous suspensions. It was found that the reinforcing effect is greater in the latter case. This behavior is ascribed to the sedimentation of the filler during evaporation, evidenced by scanning electron microscopy, wide angle X‐ray scattering, and dynamic mechanical analysis, and to the formation of a network of whiskers governed by a percolation mechanism. The behavior of the composite is modeled by subdividing the sample into layers with different whisker contents lying parallel to the film surface.

Systematic survey on crystalline features of algal celluloses

Algal cellulose from different origins has been analysed with special reference to the crystalline features, such as allomorphism (Iα/Iβ or triclinic/monoclinic two- phase model), dimension and uniplanar orientation behaviour of the specific crystallographic plane to the cell wall surface. Three types of cellulose were identified in the algal system: Iα-rich/broad microfibril/0.6 nm-oriented type; Iβ- dominant/flat-ribbon/0.53 nm-oriented type; and Iβ- dominant/small/random-oriented type. The first type appears to occur in more primitive organisms than the other types. The three types of algal cellulose correlate well with the arrangements of cellulose synthesizing complexes, i.e. multiple-row linear type, consolidated rosette type, and isolated rosette type, respectively. In Chara two types of crystals were found: an Iβ-dominant/ribbon shaped/0.6 nm-oriented type and an Iβ/narrow/random-oriented type. The former type, known to occur in some families of tunicates, was first identified in algal cellulose during this study. Reducing-end staining was successfully applied to microcrystal cellulose samples of Cladophorales and Zygnematales, showing that the cellulose microfibril has a parallel-chain structure for both cellulose Iα and cellulose Iβ

Infrared spectroscopy study of powder celluloses modified by Lewis acids

AbstractIt is shown that modified powder celluloses distinguish from microcrystal cellulose produced by a hydrolytic method by the presence of the modification of cellulose II and by a low index of crystallinity. © 1994 John Wiley &amp; Sons, Inc.

Visualization of the adsorption of a bacterial endo-β-1,4-glucanase and its isolated cellulose-binding domain to crystalline cellulose

Endo-β-1,4-glucanase A (CenA), a cellulase from the bacterium Cellulomonas fimi, is composed of two domains: a catalytic domain and a cellulose-binding domain. Adsorption of CenA and its isolated cellulose-binding domain (CBD·PT CenA) to Valonia cellulose microcrystals was examined by transmission electron microscopy using an antibody sandwich technique (CenA/CBD·PT CenA-αCenA IgG-protein A-gold conjugate). Adsorption of both CenA and CBD·PT CenA occurred along the lengths of the microcrystals, with an apparent preference for certain crystal faces or edges. CenA or CBD·PT CenA, but not the isolated catalytic domain, were shown to prevent the flocculation of microcrystalline bacterial cellulose. The cellulose-binding domain may assist crystalline cellulose hydrolysis in vitro by promoting substrate dispersion.

Comparison of agar and microcrystal cellulose as gelling agents forin vitro culture ofNicotiana tabacum stem expiants

Investigation was made on a use of microcrystal cellulose as a new and inexpensive gelling agent instead of agar. Microcrystal cellulose in concentration 20 % forms a suitable structure of nutrient medium for in vitro cultivation. The higher humidity in the culture container with microcrystal cellulose causes partial vitrification of Nicotiana tabacum L. plants, cv. Zlatna arda. It is proved by reduced chlorophyll content, changes in protein synthesis and strongly reduced isoenzyme spectrum of peroxidase.

Orientation of cellulose microcrystals by strong magnetic fields

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrientation of cellulose microcrystals by strong magnetic fieldsJ. Sugiyama, H. Chanzy, and G. MaretCite this: Macromolecules 1992, 25, 16, 4232–4234Publication Date (Print):August 1, 1992Publication History Published online1 May 2002Published inissue 1 August 1992https://doi.org/10.1021/ma00042a032RIGHTS & PERMISSIONSArticle Views1448Altmetric-Citations202LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts