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Wood-pulp fibres are recognized asconcentrically-layered, laminated composite tubes of structuralreinforcing material, the cellulose microfibrils, embedded in acementing matrix of hemicellulose and lignin. When the singlefibres are subjected to cyclic mechanical action, theirmorphological behaviour is characterized by the fatigue growth ofmicro-voids and surface damage which individually andcollectively...
Because cellulases are finding more applicationsin the textile and detergent industries, their effect on cottonfibres must be evaluated. For this purpose, the action of arecombinant cellulase, endoglucanase V from the fungus Humicolainsolens, has been followed by scanning electron microscopy (SEM)in classical longitudinal views as well as in cross-sections ofcotton fibres. The experiments were conducted...
More than ten β-glycosyltransferases are now recognized that have limited similarity to the amino acid sequence of cellulose synthase from Acetobacter xylinum. Using hydrophobic cluster analysis (HCA), we recently identified two domains and putative catalytic residues in the processive β-glycosyltransferases. In this study, we have found expressed sequence tags (ESTs) from higher plants (Arabidopsis...
An optimized ethanol/water processhas been employed for the pulping of fibres from sugar canebagasse. After pretreatment with aqueous NaOH, unbleached pulpswere subjected to benzylation at 110 °C for differentperiods of time. The resulting purified products werecharacterized by thermogravimetric analysis (TGA), differentialscanning calorimetry (DSC), gel permeation chromatography (GPC)and infrared...
More than ten β-glycosyltransferases are now recognized that have limitedsimilarity to the amino acid sequence of cellulose synthase fromAcetobacter xylinum. Using hydrophobic cluster analysis (HCA), werecently identified two domains and putative catalytic residuesin the processive β-glycosyltransferases. In this study, wehave found expressed sequence tags (ESTs) from higher plants(Arabidopsis thaliana,...
Because cellulases are finding more applications in the textile and detergent industries, their effect on cotton fibres must be evaluated. For this purpose, the action of a recombinant cellulase, endoglucanase V from the fungus Humicola insolens, has been followed by scanning electron microscopy (SEM) in classical longitudinal views as well as in cross-sections of cotton fibres. The experiments were...
Wood-pulp fibres are recognized as concentrically-layered, laminated composite tubes of structural reinforcing material, the cellulose microfibrils, embedded in a cementing matrix of hemicellulose and lignin. When the single fibres are subjected to cyclic mechanical action, their morphological behaviour is characterized by the fatigue growth of micro-voids and surface damage which individually and...
An optimized ethanol/water process has been employed for the pulping of fibres from sugar cane bagasse. After pretreatment with aqueous NaOH, unbleached pulps were subjected to benzylation at 110 °C for different periods of time. The resulting purified products were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and infrared...
Medical tablet forming ability of microcrystalline cellulose (MCC) was investigated in relation to the mobility of water molecules in MCC particles. For this purpose, the spin-lattice relaxation time T1 of water in the system was measured by 1H-NMR. Over a wide range of water contents (0.02 ≤ H2O/cellulose (g/g) ≤ 1.79), two different T1 (T1,l and T1,s) values were observed for water in each MCC sample...
Structural changes in never- dried, disintegrated bacteria l cellulose by treatment with aqueous NaOH were examined by electron microscopy, X-ray diffractometry and acid hydrolysis behaviour and compared with those of cotton cellulose. The microfibril kept its fibrillar morphology after treatment with NaOH solutions of less than 9% (w/w), but changed into irregular aggregates when treated with NaOH...
Novel cellobiose derivatives, 6-O-methyl, 6′-O-methyl, 6,6′-di-O-methyl- β-cellobiosyl fluorides, have been prepared and their hydrolytic behaviour as well as polymerizability by a purified cellulase from Trichoderma viride were investigated. Among these compounds, 6-O-methyl-β-cellobiosyl fluoride was found to polymerize by the cellulase catalysis in a mixed solvent of acetonitrile and acetate buffer...
Two homologous series of regio- selectively sub stituted cellulose: 3-O-benzyl-2, 6-di-O-pivaloyl derivatives (Series 1) and 2,3,6-tri-O-acetyl derivatives (Series 2) up to an eicosamer (DP = 20), were synthesized for the first time by elongation of the carbohydrate chain from cellooctaose derivative 5 and subsequent deprotection. Some changing properties of the homologous series with increasing DP...
Cellulose alkyl esters, CELL- OCOCnH2n+1(n = 1 ∼ 6), were synthesized by a homogeneous reaction of cotton cellulose with different acyl chlorides in N,N-dimethylacetamide--lithium chloride solution. The miscibility of the esterified celluloses with poly(∈-caprolactone) (PCL) was investigated, mainly through thermal analysis by differential scanning calorimetry (DSC). A polymer pair, cellulose butyrate...
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;...
Low molecular weight cellulose (degree of polymerization = ca 15) was dissolved in 4-- 30% NaOD/D2O, and relationships between 1H- and 13C-chemical shifts of the cellulose and NaOD concentrations were studied in terms of the dissociation of three hydroxyl groups of cellulose in aqueous NaOH solutions. All C---H proton resonances were shifted upfield linearly with an increase in the NaOD concentration,...
Comb-shaped, amphiphilic O-(2- hydroxy-3-butoxypropyl) cellulose (HBPC) was prepared by a homogeneous reaction of cellulose with butyl glycidyl ether (BGE) in a 10% (w/w) LiCl--DMAc solution. It was found that: (a) the molar substitution (MS) of water-soluble HBPC ranges from 0.4 to 1.0, and is nearly equal to its degree of substitution (DS), indicating that the HBPC derivatives obtained are comb-shaped...
Triethylamine-mediated carboxymethylation of ethyl cellulose using monochloroacetic acid produced a hydroxymethyl acetate derivative (I). The derivative (I) was subsequently converted to a phthalimidoethyl-ethyl cellulose ether derivative by reacting it with β-hydroxyethyl phthalimide using concentrated sulphuric acid as the catalyst. The elemental analysis agreed with the calculated values using...
Atomic force microscopy (AFM), tapping mode atomic force microscopy (TM-AFM) and transmission electron microscopy (TEM) have been used to image the cell wall, ultrathin sections of whole cells and cellulose microfibrils prepared from the green alga Micrasterias denticulata. Measurements of the microfibril dimensions are in agreement with earlier observations carried out by electron microscopy. Images...
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