Showing papers on "Cellulose published in 1993"
Book•
01 Jan 1993
TL;DR: In this article, the authors bring together accepted concepts on the molecular structure, fine structure and morphology of cellulose, and examine the interrelation between the structure and the accessibility of fibrous cellulose substrates.
Abstract: This text aims to bring together accepted concepts on the molecular structure, fine structure and morphology of cellulose, and to examine the interrelation between the structure and the accessibility of fibrous cellulose substrates.
506 citations
417 citations
TL;DR: Woody tissues are composed mainly of three biopoly- mers: cellulose; hemicellulose; and lignin, a highly irregular aromatic polymer which serves to pro- vide strength and structure to the tissue.
360 citations
TL;DR: The results are discussed on the basis of a kinetic isotope effect on the fructose-1,6-bisphosphate aldolase reaction and of metabolic branching on the level of the triose phosphates with varying substrate fluxes to determine the relative carbon isotope ratio of primary and secondary products from different compartments of annual plants, pine needles, wood, and decomposing Basidiomycets.
Abstract: Relative carbon isotope ratio ([delta]13C values) of primary and secondary products from different compartments of annual plants, pine needles, wood, and decomposing Basidiomycetes have been determined. An enrichment in 13C was found for storage tissues of annual plants, because of the high level of the primary storage products sucrose and starch; however, the enrichment was even greater in leaf starch. All of these compounds had the same relative 13C enrichment in positions 3 and 4 of glucose. Secondary products in conifer needles (lignin, lipids) were depleted in 13C by 1 to 2 [per mille (thousand) sign] relative to carbohydrates from the same origin. Air pollution caused a small decrease in [delta]13C values; however, the relative content of plant products, especially of the soluble polar compounds, was also affected. Decomposing fungi showed a global accumulation of 13C by 4[per mille (thousand) sign] relative to their substrates in wood. Their chitin was enriched by 2[per mille (thousand) sign] relative to the cellulose of the wood. Hence, Basidiomycetes preferentially metabolize “light” molecules, whereas “heavy” molecules are preferentially polymerized. Our results are discussed on the basis of a kinetic isotope effect on the fructose-1,6-bisphosphate aldolase reaction and of metabolic branching on the level of the triose phosphates with varying substrate fluxes.
337 citations
TL;DR: The model was regressed to the collected data to determine the values of the enzyme parameters and was found to satisfactorily predict the kinetics of cellulose hydrolysis, and Cellobiose and glucose were identified as the strongest inhibitors of cellulase and β‐glucosidase, respectively.
Abstract: The biochemical conversion of cellulosic biomass to ethanol, a promising alternative fuel, can be carried out efficiently and economically using the simultaneous saccharification and fermentation (SSF) process. The SSF integrates the enzymatic hydrolysis of cellulose to glucose, catalyzed by the synergistic action of cellulase and beta-glucosidase, with the fermentative synthesis of ethanol. Because the enzymatic step determines the ethanol. Because the enzymatic step determines the availability of glucose to the ethanologenic fermentation, the kinetic of cellulose hydrolysis by cellulase and beta-glucosidase and the susceptibility of the two enzymes to inhibition by hydrolysis and fermentation products are of significant importance to the SSF performance and were investigated under realistic SSF conditions. A previously developed SSF mathematical model was used to conceptualize the depolymerization of cellulose. The model was regressed to the collected data to determine the values of the enzyme parameters and was found to satisfactorily predict the kinetics of cellulose hydrolysis. Cellobiose and glucose were identified as the strongest inhibitors of cellulase and beta-glucosidase, respectively. Experimental and modeling results are presented in light of the impact of enzymatic hydrolysis on fuel ethanol production.
319 citations
TL;DR: Sophorolipid had the greatest effect on cellulose hydrolysis when it was present from the beginning of the experiment and when the enzyme/cellulose ratio was low.
Abstract: The effect of surfactants on the heterogeneous enzymatic hydrolysis of Sigmacell 100 cellulose and of steam-exploded wood was studied. Certain biosurfactants (sophorolipid, rhamnolipid, bacitracin) and Tween 80 increased the rate of hydrolysis of Sigmacell 100, as measured by the amount of reducing sugar produced, by as much as seven times. The hydrolysis of steam-exploded wood was increased by 67% in the presence of sophorolipid. At the same time, sophorolipid was found to decrease the amount of enzyme adsorbed onto the cellulose at equilibrium. Sophorolipid had the greatest effect on cellulose hydrolysis when it was present from the beginning of the experiment and when the enzyme/cellulose ratio was low.
272 citations
TL;DR: Acetobacter xylinum 1FO 13693 was selected as the best cellulose-producing bacterium among 41 strains belonging to the genus Acetobacteria and Agrobacterium because it was found to be produced at the liquid surface in static liquid cultivation.
251 citations
TL;DR: Investigation of changes in cell wall chemical composition and polymer size in the root tip of intact cotton seedlings grown in saline environments found a significant increase in the cell wall uronic acid content, but a reduction in cellulose content on a per unit dry weight basis.
Abstract: The aim of this study was to investigate changes in cell wall chemical composition and polymer size in the root tip of intact cotton seedlings (Gossypium hirsutum L. cv. Acala SJ-2) grown in saline environments, in order to relate the interaction between high salinity and root growth to possible changes in cell wall metabolism. Cotton seedlings were grown in modified Hoagland nutrient solution with various combinations of NaCl and CaCl 2 . Cell walls were fractionated into four fractions (pectin, hemicellulose 1 and 2, cellulose), and analysed for their total sugar content, neutral sugar composition and size of polysaccharides. At 1 mol m −3 Ca, 150 mol m −3 NaCl resulted in a significant increase in the cell wall uronic acid content, but a reduction in cellulose content on a per unit dry weight basis
223 citations
TL;DR: The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution.
Abstract: Two separate assay systems were used to evaluate the biodegradation potential of cellulose acetate: an in vitro enrichment cultivation technique (closed batch system), and a system in which cellulose diacetate (CDA) films were suspended in a wastewater treatment system (open continuous feed system). The in vitro assay employed a stable enrichment culture, which was initiated by inoculating a basal salts medium containing cellulose acetate with 5% (v/v) activated sludge. Microscopic examination revealed extensive degradation of CDA (DS = 2.5) fibers after 2–3 weeks of incubation. Characterization of the CA fibers recovered from inoculated flasks demonstrated a lower average degree of substitution and a change in the mol wt profiles. In vitro enrichments with CDA (DS = 1.7) films were able to degrade > 80% of the films in 4–5 days. Cellulose acetate (DS = 2.5) films required 10–12 days for extensive degradation. Films prepared from cellulose triacetate remained essentially unchanged after 28 days in the in vitro assay. The wastewater treatment assay was less active than the in vitro enrichment system. For example, approximately 27 days were required for 70% degradation of CDA (DS = 1.7) films to occur while CDA (DS = 2.5) films required approximately 10 weeks before significant degradation was obtained. Supporting evidence for the biodegradation potential of cellulose acetate was obtained through the conversion of cellulose [1-14C]-acetate to 14CO2 in the in vitro assay. The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution. © 1993 John Wiley & Sons, Inc.
205 citations
TL;DR: It is evident that the presence of a functional CBD is increasingly important for CBH I toward higher enzyme to cellulose ratios and the putative hinge removed by the first deletion facilitates CBD-driven binding and dense packing of the wild type enzyme on the cellulose surface.
202 citations
TL;DR: In this paper, the crystal transformation of Valonia cellulose induced in a dilute alkaline solution at high temperatures has been examined by high-resolution 13 C NMR spectroscopy.
Abstract: The crystal transformation of Valonia cellulose induced in a dilute alkaline solution at high temperatures has been examined by high-resolution 13 C NMR spectroscopy. The C1 and C4 resonance lines, which are characteristic triplets for the celluloses from primitive organisms, markedly undergo changes in relative intensities of the constituent lines with increasing annealing temperature, and those lines are finally converted to doublets with almost equivalent intensities. Such results were successfully analyzed interms of the composite crystal model in which native cellulose crystals are assumed to be composites of two allomorphs, celluloses I α and I β , resulting in confirmation of the validity of the composite crystal model
TL;DR: In this paper, the effect of added powdered cellulose and methyl cellulose on oil uptake during deep-fat frying of donuts and falafel balls was determined, and a new criterion, UR, expressing the oil uptake ratio between the weight of oil uptake and the water removed was introduced.
Abstract: The effect of added powdered cellulose and methyl cellulose on oil uptake during deep-fat frying of donuts and falafel balls was determined. A new criterion, UR, expressing the oil uptake ratio between the weight of oil uptake and the weight of water removed was introduced. This criterion was valuable in assessing effectiveness of reducing oil uptake during deep-fat frying. Methocel was significantly more effective than powdered cellulose in reducing oil uptake.
TL;DR: In this article, the authors describe the noncatalytic conversion of cellulose in supercritical and subcritical water and demonstrate that even without any acid catalyst, cellulose was rapidly converted to water soluble species with a relatively high glucose yield in near critical water and glucose yield increased with elevating temperature.
Abstract: This paper describes the noncatalytic conversion of cellulose in supercritical and subcritical water. First, it was demonstrated that even without any acid catalyst, cellulose was rapidly converted to water soluble species with a relatively high glucose yield in near critical water and glucose yield increased with elevating temperature. Then the rate constants for cellulose decomposition and glucose decomposition were evaluated at a pressure of 25 MPa over a temperature ranging from 473 K to 673 K by using semi-batch reactor and a flow reactor, respectively. From the reported cellulose pyrolysis rate constant and the evaluated cellulose decomposition rate constant, cellulose hydrolysis rate constant was evaluated. By using the cellulose hydrolysis rate, cellulose pyrolysis rate and the glucose decomposition rate, glucose yield obtained in the semi-batch experiment was reasonably explained.
TL;DR: This CBD is of particular interest because it is the first CBD from a completely sequenced nonenzymatic protein shown to be an independently functional domain and suggests that the CBD recognition site is larger than a simple cellobiose unit or more complex than a repeatingcellobiose moiety.
Abstract: Cellulose-binding protein A (CbpA), a component of the cellulase complex of Clostridium cellulovorans, contains a unique sequence which has been demonstrated to be a cellulose-binding domain (CBD). The DNA coding for this putative CBD was subcloned into pET-8c, an Escherichia coli expression vector. The protein produced under the direction of the recombinant plasmid, pET-CBD, had a high affinity for crystalline cellulose. Affinity-purified CBD protein was used in equilibrium binding experiments to characterize the interaction of the protein with various polysaccharides. It was found that the binding capacity of highly crystalline cellulose samples (e.g., cotton) was greater than that of samples of low crystallinity (e.g., fibrous cellulose). At saturating CBD concentration, about 6.4 mumol of protein was bound by 1 g of cotton. Under the same conditions, fibrous cellulose bound only 0.2 mumol of CBD per g. The measured dissociation constant was in the 1 microM range for all cellulose samples. The results suggest that the CBD binds specifically to crystalline cellulose. Chitin, which has a crystal structure similar to that of cellulose, also was bound by the CBD. The presence of high levels of cellobiose or carboxymethyl cellulose in the assay mixture had no effect on the binding of CBD protein to crystalline cellulose. This result suggests that the CBD recognition site is larger than a simple cellobiose unit or more complex than a repeating cellobiose moiety. This CBD is of particular interest because it is the first CBD from a completely sequenced nonenzymatic protein shown to be an independently functional domain.
TL;DR: It is proposed that hemicelluloses may be primary moderators of the tertiary structure of cell wall celluloses, allowing the development of a wide range of properties.
TL;DR: All enzymes produced new reducing end groups on both substrates, and thus none of them is a true exo-cellulase, and both the rate of formation and the amount was considerably higher for the EG enzymes than for the CBH's, which may justify the classification of cellulases into two groups, although the difference is quantitative rather than qualitative.
TL;DR: The enzymatic hydrolysis of cellulose was initially investigated using the alkaline peroxide-treated fraction derived from steam-exploded Eucalyptus viminalis chips and a cellulase mixture of the commercial Celluclast and Novozym preparations and most of the cellulase activity was shown to be associated with the undydrolyzed residue.
TL;DR: The use of whole P .
Abstract: Publisher Summary This chapter describes physicochemical and biological treatments for enzymatic or microbial conversion of LignocelIulosic Biomass. Microbial utilization of the inexhaustible lignocellulosic biomass for the production of industrial chemicals, liquid fuels, protein-rich food and feed, and the preparation of cellulose polymers is an attractive approach to help meet energy and food demands. Lignocelluloses contain cellulose, hemicellulose, and lignin as the major components. Lignocellulosic raw materials by the virtue of their structure are relatively refractory to direct bioconversion. Cellulose in lignocellulosic substrates has the regions of a highly resistant crystalline structure and the lignin surrounding cellulose forms a physical barrier that allows only limited sites available for enzymatic attack. The use of whole P . chrysosporium cells and lignolytic enzymes in the pulp and paper industry appears to hold promise in processes designed for biopulping and biobleaching and in decolorizing bleach plant effluents. This can have a favorable impact on the world economy, sparing scarce energy sources and alleviating the current environmental problems with waste effluents.
TL;DR: In this article, the surface properties of cellulose fibers have been modified by heat treatment, by silane coupling agents, and by maleated polypropylene grafts, which yielded information on the fibers' acid/base interaction potential.
Abstract: The surface properties of cellulose fibers have been modified by heat treatment, by silane coupling agents, and by maleated polypropylene grafts. The effectiveness of these methods has been evaluated by electron spectroscopy (ESCA), by contact angle measurements, and by inverse gas chromatography. The latter analyses yielded information on the fibers' acid/base interaction potential. Cellulose was found to be amphoteric, with prevalent acidic properties. Heat and chloro-silane treatments accentuated acidity, while amino-silane treatment produced net basicity in the fiber surface. Modification with maleated polypropylene reduced specific interactions and converted the fiber to a predominantly dispersion-force solid. The modified fibers were used in composites with polypropylene (neutral), polystyrene (base), and chlorinated polyethylene (acid) as matrix. Stress/strain and dynamic mechanical parameters were found to vary with acid/base interactions between polymer and fiber, significant improvements being noted in elastic and storage moduli, in tensile strength and elongation. In polypropylene, properties were unaffected by acid/base considerations. Acid/base forces, not necessarily dominant, merit consideration in the design of surface modification strategies intended to optimize composite mechanical properties.
TL;DR: A third cellulase, endoglucanase V, is reported, structurally distinct from the previously determined cellulases but is similar to a recently characterized plant defence protein, despite the lack of structural similarity between these two enzymes.
Abstract: CELLULOSE is the major polysaccharide component of plant cell walls and is the most abundant organic compound on the planet. A number of bacterial1 and fungal2 organisms can use cellulose as a food source, possessing cellulases (cellobiohydrolases and endoglucanases) that can catalyse the hydrolysis of the β-(1,4) glycosidic bonds. They can be classified into seven distinct families3. The three-dimensional structures of members of two of these families are known4,5. Here we report the structure of a third cellulase, endoglucanase V, whose sequence is not represented in any of the above families. The enzyme is structurally distinct from the previously determined cellulases but is similar to a recently characterized plant defence protein6. The active site region resembles that of lysozyme, despite the lack of structural similarity between these two enzymes.
TL;DR: In this article, the action of Trichoderma cellulases on the various characteristics of cellulosic fractions obtained from pretreated eucalyptus chips was investigated, and a screened fraction derived from a fully bleached kraft pulp (FBEP-48 fraction) was shown to consist of fibers with an average fiber length and an average degree of polymerization (DP) considerably higher than that obtained for the screened fraction obtained from SO2-impregnated steam-exploded EucalyPTus chips which had been post-treated with alkaline hydrogen peroxide
TL;DR: The entire Cex exoglucanase from Cellulomonas fimi and the Cex Cellulose Binding Domain were expressed as fusions to an Lpp-OmpA hybrid which had been shown earlier to direct a heterologous protein to the cell surface.
Abstract: The entire Cex exoglucanase from Cellulomonas fimi and the Cex Cellulose Binding Domain (CBDCex) were expressed in Escherichia coli as fusions to an Lpp-OmpA hybrid which had been shown earlier to direct a heterologous protein to the cell surface. Both Cex and CBDCex were readily localized on the cell surface and could be detected by immunofluorescence microscopy, whole cell ELISAs and functional assays. In cells expressing the entire Cex, about 90% of the total cellobiose hydrolase activity was anchored on the external side of the outer membrane and was susceptible to protease (papain) added in the extracellular fluid. Cells expressing either Cex or CBDCex bound tightly and rapidly to cellulosic materials such as cotton fibers. This property can be exploited for the preparation of immobilized microbial biocatalysts via adsorption to cellulose and for cell separation through specific agglutination on inexpensive cellulosic materials. In addition, our results demonstrate the general utility of fusions to lpp-ompA for the efficient display of proteins and the engineering of the surface topology of Gram-negative bacteria.
TL;DR: Although xylanase was produced efficiently on cellulose as well as on xylan as the carbon source, significant production of cellulose was observed only on the cellulose-based medium and best production was at lower pH (4.0 minimum).
Abstract: Trichoderma reesei VTT-D-86271 (Rut C-30) was cultivatedon media based on cellulose and xylan as the main carbon source in fermentors with different pH minimum controls. Production of xylanase was favoured by a rather high pH minimum control between 6.0 and 7.0 on both cellulose- and xylan-based media. Although xylanase was produced efficiently on cellulose as well as on xylan as the carbon source, significant production of cellulose was observed only on the cellulose-based medium and best production was at lower pH (4.0 minimum). Production of xylanase at pH 7.0 was shown to be dependent on the nature of the xylan in the cultivation medium but was independent of other organic components. Best production of xylanase was observed on insoluble, unsubstituted beech xylan at pH 7.0. Similar results were obtained in laboratory and pilot (200-l) fermentors. Downstream processing of the xylanase-rich, low-cellulose culture filtrate presented no technical problems despite apparent autolysis of the fungus at the high pH. Enzyme produced in the 200-l pilot fermentor was shown to be suitable for use in enzyme-aided bleaching of kraft pulp. Due to the high xylanase/cellulase ratio of enzyme activities in the culture filtrate, pretreatment for removal of cellulase activity prior to pulp bleaching was unnecessary.
TL;DR: In this article, the thermal decomposition of Avicel cellulose was studied by non-isothermal differential scanning calorimetry in hermetically sealed sample holders and the experimental results showed a marked catalytic effect of the water on the cellulose decomposition.
Patent•
09 Mar 1993
TL;DR: In this paper, a process for the production of anhydrosugars such as levoglucosan (1,6-anhydro-β-Dglucopyranose), from liquids obtained by the fast thermal pyrolysis of pretreated lignocellulosics or celluloses is described.
Abstract: A process is described for the production of anhydrosugars such as levoglucosan (1,6-anhydro-β-D-glucopyranose), from liquids obtained by the fast thermal pyrolysis of pretreated lignocellulosics or celluloses. In this process, the pyrolytic liquids containing the anhydrosugars are produced with a substantially reduced amount of lignin-derived components by using as feedstock materials which have been previously delignified and then pretreated, or by preferential oxidation of the lignin fraction of a pretreated biomass during pyrolysis. The preparation from pretreated biomass of pyrolytic liquors from which the lignin derived chemical products of fast pyrolysis are absent or in low concentrations permits simpler and more economical recovery of crystalline levoglucosan and other anhydrosugars, or a more economical preparation of readily fermentable aqueous sugar solutions therefrom. A new procedure for the recovery of crystalline levoglucosan from such solutions is described.
TL;DR: The performance and the efficiency of several cellulose derivatives as a molecular sieving agent for the capillary electrophoretic separation of DNA restriction fragments were investigated and guidelines are presented for choosing these parameters, depending on the size of the DNA fragments being separated.
TL;DR: In this paper, the authors used N,N-dicyclohexylcarbodiimide (DCC) and 4-pyrrolidinopyridine (PP) activators for cellulose propionates to stearates with DS ranging between <0·1 and 2·5.
TL;DR: In this paper, the mechanism of esterification of cotton cellulose by a polycarboxylic acid was investigated using Fourier transform infrared spectroscopy (FT-IR).
Abstract: The mechanism of esterification of cotton cellulose by a polycarboxylic acid was investigated using Fourier transform infrared spectroscopy (FT-IR). The infrared spectroscopic data indicate that a polycarboxylic acid esterifies with cotton cellulose through the formation of an acid anhydride intermediate. A five-member cyclic anhydride intermediate was identified in the cotton fabric treated with poly(maleic acid). The five-member cyclic anhydride is a reactive intermediate and readily esterifies when reaction sites are available. We also found that those polycarboxylic acids, which form five-member cyclic anhydride intermediates, crosslink cotton cellulose more effectively than those polycarboxylic acids which form six-member cyclic anhydride intermediates. © 1993 John Wiley & Sons, Inc.
TL;DR: A new substrate for mammalian cell culture was developed using a cellulose membrane produced by acetobacter aceti through modification of the ionic charge of the membrane and adsorption of collagen to it, which promoted cellular adhesion to the membrane surface.
Abstract: A new substrate for mammalian cell culture was developed using a cellulose membrane produced by Acetobacter aceti Modification of the ionic charge of the membrane and adsorption of collagen to it promoted cellular adhesion to the membrane surface The growth of eight kinds of cells on the membrane, was comparable to that achieved in plastic Petri dishes The membrane was tested for use in the production of recombinant Erythroid Differentiation Factor (EDF)/activin A using genetically engineered Chinese hamster ovary cells Both the viability of the cells and production of EDF/activin A were maintained for about 1 month, while cultures on plastic dishes lasted only 12 days It was considered that the mechanism of improved cell viability was related to the ultrastructure of the cellulose membrane
TL;DR: In this article, the influence of inorganic ion content on the thermal decomposition of cellulose was studied by using X-ray scattering, elemental analysis, TGA and FT-IR.