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PubMed2005

The cellulose/lignin assembly assessed by molecular modeling. Part 1: adsorption of a threo guaiacyl beta-O-4 dimer onto a Ibeta cellulose whisker.

The assembly of the two major cell wall components, cellulose and lignin, were investigated at the atomistic scale using molecular dynamics simulations. To this end, a molecular model of a cellulose crystal corresponding to the allomorph Ibeta and exhibiting different surfaces was considered to mimic the carbohydrate matrix present in native wood cell wall. The lignin model compound considered here is a threo guaiacyl beta-O-4 dimer. The dynamical process of adsorption of the lignin dimer onto the different surfaces of the cellulose crystal was examined. The modes of association between the two constituents were analyzed; energies of adsorption of the dimer are calculated favorable and of the same order of magnitude on all sides of the cellulosic model, suggesting that the deposition of lignin precursors onto cellulose fibers is non-specific from an enthalpic point of view. Interestingly, geometrical characteristics and energetical details of the adsorption are surface-dependent. Computed data have underlined the predominant contribution of van der Waals interactions for adsorption onto the (200) face, as well as the major influence of H-bonding interactions in the dynamical process of adsorption onto (110) and (1-10) faces. A large number of adsorption sites have been identified and a noticeable "flat" geometry of adsorption of the lignin dimer has been observed, as a consequence of the stacking interactions between lignin aromatic rings and C-H groups of cellulose. Importantly, these dispersive interactions lead to a preferential parallel orientation of lignin aromatic rings relative to the cellulose surface, notably on the (200) face. Such a parallel orientation is consistent with previously reported experimental observations.

Adsorption↗
PubMed1992

Comparison of the peritoneal cells elicited by oxidized regenerated cellulose (Interceed) and expanded polytetrafluoroethylene (Gore-Tex Surgical Membrane) in a murine model.

OBJECTIVE: The peritoneal fluid cell responses to the available barriers used to prevent postoperative adhesions, oxidized regenerated cellulose (interceed) and expanded polytetrafluoroethylene (Gore-Tex Surgical Membrane), were compared. STUDY DESIGN: Oxidized regenerated cellulose and expanded polytetrafluoroethylene were inserted into the peritoneal cavity of mice and the peritoneal fluid cell number, differential cell count, morphologic type, adherence to plastic, and phorbol-12,13-myristate acetate-stimulated hydrogen peroxide production evaluated. Peritoneal fluid cell attachment to oxidized regenerated cellulose and expanded polytetrafluoroethylene was evaluated by electron microscopy. RESULTS: Oxidized regenerated cellulose promptly elicited increased numbers of large, morphologically activated peritoneal fluid macrophages that adhered more rapidly and produced more hydrogen peroxide than controls. Expanded polytetrafluoroethylene gradually increased the number of normal-appearing peritoneal fluid macrophages with increased hydrogen peroxide production but normal adherence. Macrophages rapidly attached to both materials in vivo, with oxidized regenerated cellulose being rapidly degraded. CONCLUSION: Oxidized regenerated cellulose, to a greater extent than expanded polytetrafluoroethylene, elicits an acute peritoneal fluid inflammatory exudate in the mouse, which may contribute to the oxidized regenerated cellulose-induced peritoneal injury and de novo adhesions observed in this model.

Animals↗
PubMed1997

Interaction of Interceed oxidized regenerated cellulose with macrophages: a potential mechanism by which Interceed may prevent adhesions.

OBJECTIVE: The objective of the study was to determine whether Interceed oxidized regenerated cellulose (Johnson & Johnson Medical, Arlington, Tex.), because of its polyanionic nature, may compete for the macrophage scavenger receptor. STUDY DESIGN: RAW macrophages were incubated with Interceed oxidized regenerated cellulose and known scavenger receptor ligands. The production of interleukin-1beta by mouse peritoneal macrophages was measured in the presence of Interceed cellulose. RESULTS: When macrophages were incubated with Interceed cellulose, increasing concentrations inhibited the uptake of fluorescent acetyl low-density lipoprotein. In the presence of Interceed cellulose there was a decrease in the production of interleukin-1beta by mouse macrophages. CONCLUSION: These results suggest that the interaction of Interceed oxidized regenerated cellulose with macrophages with scavenger receptors may result in a decreased secretion of matrix components, inflammatory mediators, and cellular growth factors. Thus Interceed cellulose may function as a biologic barrier in preventing adhesions.

Animals↗
PubMed2001

Anticoagulant potential of regioselective derivatized cellulose.

Regioselective derivatization was carried out introducing sulfate, phosphate or quaternary ammonia groups in C2-, C3- and C6-position of the anhydroglycose unit of cellulose. The anticoagulant potential of these derivatives was estimated with common clotting assays, such as thrombin time and partial thromboplastin time. It was found that a pronounced anticoagulant activity of cellulose derivatives could be achieved if the degree of substitution (DS) with sulfate was above 1.0. The anticoagulant activity was maximal at a DS of about 1.5 and then decreased again. Further, it was detected that particularly sulfation in C2-position resulted in a pronounced anticoagulant activity of cellulose derivatives. Development and application of assays specific for thrombin and factor Xa indicated that the anticoagulant potential of these cellulose derivatives was mainly due to anti-thrombin activity. The comparison of cellulose sulfates and cellulose derivatized with phosphate and quaternary ammonium groups demonstrated that the negative charge and type of the substituent is an important prerequisite for the anticoagulant activity of cellulose derivatives. Indeed, derivatization with sulfate produced superior activity in comparison with phosphate.

Anticoagulants↗
PubMed1996

Interaction of polysaccharides with the N-terminal cellulose-binding domain of Cellulomonas fimi CenC. 1. Binding specificity and calorimetric analysis.

The carbohydrate-binding specificity of the N-terminal cellulose-binding domain (CBDN1) from Cellulomonas fimi beta-1,4-glucanase C (CenC) was investigated using affinity electrophoresis, binding assays and microcalorimetry in parallel with NMR and difference ultraviolet absorbance spectroscopy [Johnson, P.E., Tomme, P., Joshi, M.D., & McIntosh, I., P. (1996) Biochemistry 35, 13895-13906]. Binding of CBDN1 on insoluble cellulose is distinctly different from other cellulose-binding domains. CBDN1 binds amorphous cellulose (phosphoric acid-swollen) with high affinity (Kr = 5.1 L g-1), binds Avicel weakly and does not bind highly crystalline bacterial or tunicin cellulose. Moreover, CBDN1 binds soluble cellooligosaccharides and beta-1,4-linked oligomers of glucose such as hydroxyethycellulose, soluble beta-1,3-1,4-glucans from barley and oat, but has no affinity for alpha-1,4-, beta-1,3-, or beta-1,6-polymers of glucose. This is the first report of a cellulose-binding domain with strong and specific affinity for soluble glycans. The thermodynamics for binding of CBDN1 to oligosaccharides, soluble glycans, and phosphoric acid-swollen cellulose were investigated by titration microcalorimetry. At least four beta-1,4-linked glucopyranosides are required to detect binding. For larger glucans, with five or more glucopyranoside units, the binding constants and standard free energy changes are virtually independent of the glucan chain length, indicating that cellopentaose completely fills the binding site. Binding is moderately strong with binding constants ranging from 3,200 +/- 500 M-1 for cellotetraose, to 25,000 +/- 3,000 M-1 for the larger sugars. The reactions are controlled by favorable standard free enthalpy changes which are compensated in a linear fashion by a significant decrease in entropy. A predominance of polar interactions such as hydrogen bonding together with van der Waals interactions provide the major driving forces for the binding event.

Actinomycetales↗
PubMed2001

"Nematic ordered cellulose": a concept of glucan chain association.

Native cellulose consists of a set of parallel chains composed of glucose. Most of the time, these chains are highly ordered and form a structure that is known as a microfibril. On the other hand, highly crystalline forms of cellulose are more difficult to process and often are unpredictable in their behavior. If an ordered but noncrystalline form of cellulose could be produced, this would greatly extend the possibilities of usage of cellulose to new areas. In this paper, we have produced such a new supermolecular structure of cellulose, called nematic ordered cellulose. The unique characteristics of this supermolecular structure of cellulose have been clarified using various kinds of physicochemical analyses. Using a high-resolution transmission electron microscopic approach, we have also imaged the single glucan chains, demonstrating the close but nonprecise association usually found in crystalline biopolymers.

Carbohydrate Conformation↗
PubMedDate not supplied

Preparation of ultrafine oxidized cellulose mats via electrospinning.

Ultrafine oxidized cellulose (OC) mats were prepared by oxidation of ultrafine cellulose mats produced by electrospinning and subsequent deacetylation of cellulose acetate for potential applications in nonwoven adhesion barriers. When ultrafine cellulose mats were oxidized with a mixture of HNO3/H3PO4 - NaNO2 (2/1/1.4 v/v/wt %), their ultrafine mat structure remained unchanged. The yield and carboxyl content of OC mats were 86.7% and 16.8%, respectively. OC showed lower crystallinity than cellulose because the oxidation of cellulose proceeded via disruption of hydrogen bonds between cellulose chains. The swelling behaviors of ultrafine OC mats were dependent on the type of swelling solution. In a physiological salt solution, their degree of swelling was approximately 230%.

Absorption↗
PubMedDate not supplied

Covalent immobilization of cellulose layers onto maleic anhydride copolymer thin films.

Thin films of cellulose are advantageous for analytical studies in aqueous environments to investigate various factors determining the performance of cellulose-based products. However, the weak fixation of cellulose layers on common carrier materials often limits this approach. To address this problem, we suggest a novel maleic anhydride copolymer precoating technique which allows for the covalent attachment of cellulose thin films through esterification. Maleic anhydride copolymers were deposited and covalently bound onto planar, aminosilane-modified glass or silicon oxide surfaces. Cellulose was subsequently immobilized on top of the copolymer precoatings by spin coating from N-methylmorpholine-N-oxide/dimethyl sulfoxide solutions. The resulting cellulose films were thoroughly characterized with respect to layer thickness, morphology, chemical constitution, and electrical charging. The stability of the layers against shear stress was demonstrated in aqueous solutions and the covalent attachment of the cellulose to the copolymer films was proven by means of dissolution experiments followed by ellipsometry and high-resolution X-ray photoelectron spectroscopy.

Cellulose↗
PubMed2007

The future prospects of microbial cellulose in biomedical applications.

Microbial cellulose has proven to be a remarkably versatile biomaterial and can be used in wide variety of applied scientific endeavors, such as paper products, electronics, acoustics, and biomedical devices. In fact, biomedical devices recently have gained a significant amount of attention because of an increased interest in tissue-engineered products for both wound care and the regeneration of damaged or diseased organs. Due to its unique nanostructure and properties, microbial cellulose is a natural candidate for numerous medical and tissue-engineered applications. For example, a microbial cellulose membrane has been successfully used as a wound-healing device for severely damaged skin and as a small-diameter blood vessel replacement. The nonwoven ribbons of microbial cellulose microfibrils closely resemble the structure of native extracellular matrices, suggesting that it could function as a scaffold for the production of many tissue-engineered constructs. In addition, microbial cellulose membranes, having a unique nanostructure, could have many other uses in wound healing and regenerative medicine, such as guided tissue regeneration (GTR), periodontal treatments, or as a replacement for dura mater (a membrane that surrounds brain tissue). In effect, microbial cellulose could function as a scaffold material for the regeneration of a wide variety of tissues, showing that it could eventually become an excellent platform technology for medicine. If microbial cellulose can be successfully mass produced, it will eventually become a vital biomaterial and will be used in the creation of a wide variety of medical devices and consumer products.

Acetobacter↗
PubMed1981

The action on cellulose and its derivatives of a purified 1,4-beta-glucanase from Trichoderma koningii.

The specific properties have been examined of the 1,4-beta-glucanase component of Trichoderma koningii that participates in an early and effective stage of random breakdown of native cellulose to short fibres. The enzyme was purified and freed from associated components of the cellulase complex (particularly beta-glucosidase) that interfere with, and complicate interpretation of, the action of such enzymes. Purification increased the specific activity 25-fold over culture filtrates; the enzyme hydrolysed CM-cellulose faster than the purified beta-glucosidase from the same organism hydrolysed any of its substrates (cellobiose or cellodextrins). The specificity of the glucanase was directed towards soluble derivatives of cellulose, CM-cellulose and cellodextrins, and not to insoluble cellulose or alpha-linked polymers. The approximate Km was 2.5 mg of CM-cellulose . ml-1 at 37 degrees C at the optimum pH, 5.5, where enzymic activity was maximal with 6--7 mg of CM-cellulose . ml-1 and inhibited by higher concentrations. The temperature optimum was 60 degrees C. The glucanase attacked larger cellodextrins (cellohexaose to cellotetraose, in that order) much more readily than smaller dextrins (cellobiose and cellotriose) and released a mixture of products, glucose up to cellopentaose, which was quantitatively determined after chromatography on charcoal. Similar examination of hydrolysates of the reduced cellodextrins showed clearly the high specificity of the enzyme for the central bond of its natural substrates (the cellodextrins), whatever their chain length, and indicated the nature of the enzyme as an endoglucanase. Outer bonds shared a weaker, but similar, susceptibility to enzymic cleavage. Transferase activity was absent and no larger dextrins than the initial substrate were formed.

Carboxymethylcellulose Sodium↗
PubMed1994

Changes in the molecular-size distribution of insoluble celluloses by the action of recombinant Cellulomonas fimi cellulases.

Specific patterns of attacks of cotton, bacterial cellulose and bacterial microcrystalline cellulose (BMCC) by recombinant cellulases of Cellulomonas fimi were investigated. Molecular-size distributions of the celluloses were determined by high-performance size-exclusion chromatography. Chromatography of cotton and bacterial celluloses revealed single major peaks centered over progressively lower molecular-mass positions during attack by endoglucanase CenA. In advanced stages, a second peak appeared at very low average size (approx. 11 glucosyl units); ultimate weight losses were approximately 30%. The isolated catalytic domain of CenA, p30, gave results very similar to those with complete CenA. CenA did not effectively depolymerize or solubilize BMCC significantly. Molecular-size distributions of cotton and bacterial cellulose incubated with endoglucanases CenB or CenD exhibited one major peak regardless of incubation time; low-molecular-mass fragments did not accumulate. Weight losses were 40 and 35% respectively. The single peak shifted to lower-molecular-mass positions as incubation continued, but high-molecular-mass material persisted. CenB and CenD readily attacked and solubilized BMCC (approx. 70%). We conclude that CenA attacks cellulose by preferentially cleaving completely through the cellulose microfibrils at the amorphous sites, and much more slowly by degrading the crystalline surfaces. Conversely, CenB and CenD cleave the amorphous regions much less efficiently while vigorously degrading the surfaces of the crystalline regions of the microfibrils.

Cellulase↗
PubMed1998

Pseudomonas cellulose-binding domains mediate their effects by increasing enzyme substrate proximity.

To investigate the mode of action of cellulose-binding domains (CBDs), the Type II CBD from Pseudomonas fluorescens subsp. cellulosa xylanase A (XYLACBD) and cellulase E (CELECBD) were expressed as individual entities or fused to the catalytic domain of a Clostridium thermocellum endoglucanase (EGE). The two CBDs exhibited similar Ka values for bacterial microcrystalline cellulose (CELECBD, 1.62x10(6) M-1; XYLACBD, 1.83x10(6) M-1) and acid-swollen cellulose (CELECBD, 1.66x10(6) M-1; XYLACBD, 1.73x10(6) M-1). NMR spectra of XYLACBD titrated with cello-oligosaccharides showed that the environment of three tryptophan residues was affected when the CBD bound cellohexaose, cellopentaose or cellotetraose. The Ka values of the XYLACBD for C6, C5 and C4 cello-oligosaccharides were estimated to be 3.3x10(2), 1.4x10(2) and 4.0x10(1) M-1 respectively, suggesting that the CBD can accommodate at least six glucose molecules and has a much higher affinity for insoluble cellulose than soluble oligosaccharides. Fusion of either the CELECBD or XYLACBD to the catalytic domain of EGE potentiated the activity of the enzyme against insoluble forms of cellulose but not against carboxymethylcellulose. The increase in cellulase activity was not observed when the CBDs were incubated with the catalytic domain of either EGE or XYLA, with insoluble cellulose and a cellulose/hemicellulose complex respectively as the substrates. Pseudomonas CBDs did not induce the extension of isolated plant cell walls nor weaken cellulose paper strips in the same way as a class of plant cell wall proteins called expansins. The XYLACBD and CELECBD did not release small particles from the surface of cotton. The significance of these results in relation to the mode of action of Type II CBDs is discussed.

Bacterial Proteins↗
PubMed2003

Fermentation of cellulose to acetic acid by Clostridium lentocellum SG6: induction of sporulation and effect of buffering agent on acetic acid production.

AIMS: To determine the growth, correlation between sporulation and acetic acid production and effect of buffering agent at high substrate cellulose concentrations of the strain Clostiridium lentocellum SG6. METHODS AND RESULTS: The strain SG6 was grown in cellulose mineral salt medium containing cellulose (Whatman No. 1 filter paper, Whatmore International Ltd., Maidstone, UK) or cellobiose. The strain fermented cellulose even after several transfers on cellobiose medium. The formation of endospores on third day onwards indicated the lowering of pH in the medium because of the formation of acetic acid. Maintaining the pH 7.2 at higher substrate concentrations resulted in increase of biomass, cellulose fermentation, acetic acid production, etc. CONCLUSIONS: The strain SG6, with its high fermentation yields and sporulating character can become a potential strain for acetic acid production and also as a probiotic strain in animal nutrition. SIGNIFICANCE AND IMPACT OF THE STUDY: The direct conversion of cellulosic biomass to acetic acid can eliminate expensive three-step saccharification, fermentation processes. The strain SG6 can ferment cellulose at high substrate concentrations.

Acetic Acid↗
PubMed2005

Cellulose utilization by Clostridium thermocellum: bioenergetics and hydrolysis product assimilation.

The bioenergetics of cellulose utilization by Clostridium thermocellum was investigated. Cell yield and maintenance parameters, Y(X/ATP)True = 16.44 g cell/mol ATP and m = 3.27 mmol ATP/g cell per hour, were obtained from cellobiose-grown chemostats, and it was shown that one ATP is required per glucan transported. Experimentally determined values for G(ATP)P-T (ATP from phosphorolytic beta-glucan cleavage minus ATP for substrate transport, mol ATP/mol hexose) from chemostats fed beta-glucans with degree of polymerization (DP) 2-6 agreed well with the predicted value of (n-2)/n [corrected] (n = mean cellodextrin DP assimilated). A mean G(ATP)(P-T) value of 0.52 +/- 0.06 was calculated for cellulose-grown chemostat cultures, corresponding to n = 4.20 +/- 0.46. Determination of intracellular beta-glucan radioactivity resulting from 14C-labeled substrates showed that uptake is different for cellulose and cellobiose (G2). For 14C-cellobiose, radioactivity was greatest for G2; substantially smaller but measurable for G1, G3, and G4; undetectable for G5 and G6; and n was approximately 2. For 14C-cellulose, radioactivity was greatest for G5; lower but substantial for G6, G2, and G1; very low for G3 and G4; and n was approximately 4. These results indicate that: (i) C. thermocellum hydrolyzes cellulose by a different mode of action from the classical mechanism involving solubilization by cellobiohydrolase; (ii) bioenergetic benefits specific to growth on cellulose are realized, resulting from the efficiency of oligosaccharide uptake combined with intracellular phosphorolytic cleavage of beta-glucosidic bonds; and (iii) these benefits exceed the bioenergetic cost of cellulase synthesis, supporting the feasibility of anaerobic biotechnological processing of cellulosic biomass without added saccharolytic enzymes.

Adenosine Triphosphate↗
PubMed1997

Surface diffusion of cellulases and their isolated binding domains on cellulose.

The surface diffusion rate of bacterial cellulases from Cellulomonas fimi on cellulose was quantified using fluorescence recovery after photobleaching analysis. Studies were performed on an exo-beta-1-4-glycanase (Cex), an endo-beta-1-4-glucanase (CenA), and their respective isolated cellulose-binding domains (CBDs). Although these cellulose-binding domains bind irreversibly to microcrystalline cellulose, greater than 70% of bound molecules are mobile on the cellulose surface. Surface diffusion rates are dependent on surface coverage and range from a low of 2 x 10(-11) to a maximum of 1.2 x 10(-10) cm2/s. The fraction of mobile molecules increases only slightly with increasing fractional surface coverage density. Results demonstrate that the packing of C. fimi cellulases and their isolated binding domains onto the cellulose surface is a dynamic process. This suggests that the exclusion of potential CBD binding sites on the cellulose due to steric effects of neighboring bound CBDs may not fully explain the apparent negative cooperativity exhibited in CBD adsorption isotherms. Comparison with the kinetics of cellulase hydrolysis of crystalline substrate suggests that surface diffusion rates do not limit cellulase activity.

Cellulase↗
PubMed2002

Alpha-glucosidase I is required for cellulose biosynthesis and morphogenesis in Arabidopsis.

Novel mutations in the RSW1 and KNOPF genes were identified in a large-scale screen for mutations that affect cell expansion in early Arabidopsis embryos. Embryos from both types of mutants were radially swollen with greatly reduced levels of crystalline cellulose, the principal structural component of the cell wall. Because RSW1 was previously shown to encode a catalytic subunit of cellulose synthase, the similar morphology of knf and rsw1-2 embryos suggests that the radially swollen phenotype of knf mutants is largely due to their cellulose deficiency. Map-based cloning of the KNF gene and enzyme assays of knf embryos demonstrated that KNF encodes alpha-glucosidase I, the enzyme that catalyzes the first step in N-linked glycan processing. The strongly reduced cellulose content of knf mutants indicates that N-linked glycans are required for cellulose biosynthesis. Because cellulose synthase catalytic subunits do not appear to be N glycosylated, the N-glycan requirement apparently resides in other component(s) of the cellulose synthase machinery. Remarkably, cellular processes other than extracellular matrix biosynthesis and the formation of protein storage vacuoles appear unaffected in knf embryos. Thus in Arabidopsis cells, like yeast, N-glycan trimming is apparently required for the function of only a small subset of N-glycoproteins.

Arabidopsis↗
PubMed1978

Effects of force-feeding and dietary cellulose on liver lipid accumulation and lipid composition of liver and plasma in growing chicks.

Changes of content and composition of lipid in liver and plasma affected by force-feeding and dietary cellulose were investigated in 14-day old Single-Comb White Leghorn male chicks. They were given a purified high energy diet (starch-casein diet without fiber) supplemented with or without dietary cellulose. Chicks were fed ad libitum or force-fed the experimental diet. Force-feeding of excess food improved the growth rate of chicks and feed efficiency, but feeding of cellulose did not affect body weight gain and feed efficiency, though a slight improvement in nitrogen retention was observed. Liver weight and lipid content in liver and plasma were markedly elevated by force-feeding, and were markedly depressed by dietary cellulose in the force-fed chicks. It is suggested that changes of liver lipid by force-feeding and dietary cellulose are mainly originated from the changes of triglyceride in the liver lipid. No marked changes were observed in fatty acid composition of abdominal fat and liver lipid in the cellulose-fed chicks. These results suggest that dietary cellulose may affect lipid metabolism in growing chicks.

Animals↗
PubMed1986

Effects of dietary cellulose and xylan on absorption and tissue contents of zinc and copper in rats.

This investigation was undertaken to determine the effects of purified cellulose and xylan on the apparent absorption and tissue concentration of zinc and copper in male weanling Sprague-Dawley rats. The control group was fed a fiber-free diet and six other groups were fed a diet containing 3, 6 and 12% cellulose or xylan. All diets contained 10 ppm Zn and 4 ppm Cu. Four 14-d collections of feces were made during wk 3 and 4, 10 and 11, 17 and 18 and 24 and 25. The balance technique was used to measure the apparent absorption of zinc and copper. After 26 wk of consuming the test diets, rats were killed and plasma liver, kidney and mucosa analyzed. There were no significant differences between groups in regard to weight gain, feed intake and feed efficiency. The average amounts of ingested cellulose and xylan that survived the passage of the intestinal tract were 86 and 18%, respectively. Inclusion of 12% cellulose in the diet resulted in a significantly lower apparent absorption of both zinc and copper, whereas at 6% cellulose only the absorption of zinc was lower. The addition of cellulose also resulted in lower plasma zinc and liver and kidney copper concentrations. In contrast to cellulose, xylan did not exert a significant influence on apparent absorption and tissue concentrations of the minerals. Regardless of the type and level of fiber, the apparent absorption of zinc and copper declined as rats grew older.

Absorption↗