Showing papers on "Cellulose published in 1986"

Oxygen Isotope Exchange between Metabolites and Water during Biochemical Reactions Leading to Cellulose Synthesis.

Abstract: Cellulose was produced heterotrophically from different carbon substrates by carrot tissue cultures and Acetobacter xylinum (a cellulose-producing bacterium) and by castor bean seeds germinated in the dark, in each case in the presence of water having known concentration of oxygen-18 (18O). We used the relationship between the amount of 18O in the water and in the cellulose that was synthesized to determine the number and 18O content of the substrate oxygens that exchanged with water during the reactions leading to cellulose synthesis. Our observations support the hypothesis that oxygen isotope ratios of plant cellulose are determined by isotopic exchange occurring during hydration of carbonyl groups of the intermediates of cellulose synthesis.

Enhancement of enzymatic hydrolysis of cellulose by surfactant

Abstract: Effects of surfactants on enzymatic saccharification of cellulose have been studied. Nonionic, amphoteric, and cationic surfactants enhanced the saccharification, while anionic surfactant did not. Cationic and anionic surfactants denatured cellulase in their relatively low concentrations, namely, more than 0.008 and 0.001%, respectively. Using nonionic surfactant Tween 20, which is most effective to the enhancement (e.g., the fractional conversion attained by 72 h saccharification of 5 wt % Avicel in the presence of 0.05 wt % Tween 20 is increased by 35%), actions of surfactant have been examined. As the results, it was suggested that Tween 20 plays an important role in the hydrolysis of crystalline cellulose and that Tween 20 disturbs the adsorption of endoglucanase on cellulose, i.e., varies the adsorption balance of endo- and exoglucanase, resulting in enhancing the reaction. The influence of Tween 20 to the saccharification was found to remain in simultaneous saccharification and fermentation of Avicel.

Cellulose: Structure, Modification and Hydrolysis

Abstract: CELLULOSE STRUCTURE AND BIOSYNTHESIS: Natural Celluloses Recent X-Ray Crystallographic Studies of Celluloses Structure of Cellulose - Solvent Complexes Pea Cellulose and Xyloglucan: Biosynthesis and Biodegradation The Primary Cell Wall: A New Model Structure, Swelling and Bonding of Cellulose Fibers Cellulose Carbamate Description and Analysis of Cellulose Ethers Novel Methods for Accelerating Photografting of Monomers to Cellulose Anionic Graft Polymerizatoin onto Cellulose Economic Analysis of an Innovative Process for Cellulose Acetate Production Lyotropic Liquid Crystal Solutions of Cellulose Derivates Structkural Investigations on Some Cellulose Derivtives in the Crystalline and Liquid Crystaline State Appendixes Index.

Influence of lignin on digestibility of forage cell wall material.

Abstract: One-hundred-ninety-four grass samples, representing eight species, were used to determine the relationships of in vitro forage dry matter, cell wall, hemicellulose and cellulose digestibilities with lignin concentration Linear regressions indicated that dry matter digestion was inhibited to a lesser degree (P less than 05) by lignin concentration than was cell wall digestion Results for linear regressions of hemicellulose and cellulose digestibilities as functions of lignin concentration showed a greater (P less than 05) effect of lignin on cellulose digestion Smooth bromegrass and switchgrass were collected at both Clay Center and Mead, NE; for all digestibility measures, the Clay Center samples gave stronger (P less than 05) negative correlations with lignin A comparison of linear and curvilinear models indicated that, for all digestion measurements, the curvilinear model was a better (P less than 05) description of relationships with lignin concentration For all digestibility measures, lignin's inhibiting effect declined at higher lignin concentrations The curvilinear models did not show significant differences among the digestibility measures for effect of lignin The demonstration that the forage digestibility response to lignin's inhibitory effect is curvilinear in nature suggests that the mechanism of lignin's inhibition is complex

A highly active extracellular cellulase from the anaerobic rumen fungus Neocallimastix frontalis

Abstract: An extracellular cellulase which was highly active in solubilizing the highly hydrogen bond-ordered cellulose in cotton fibre was found in a culture filtrate of the anaerobic fungus, Neocallimastix frontalis, isolated from the rumen of a sheep. The cellulase was several-fold more active in solubilizing cotton fibre per unit of endo-1,4-β-glucanase than the cellulase of the aerobic fungus Trichoderma reesei mutant strain C-30, which is one of the most active cellulases isolated so far.

Kinetic, inhibition, and stability properties of a commercial β‐D‐glucosidase (cellobiase) preparation from aspergillus niger and its suitability in the hydrolysis of lignocellulose

Abstract: The rate and extent of cellulose conversion into glucose is dependent upon the amount of active ..beta..-glucosidase enzyme present in the cellulase preparation used for saccharification. This is because cellobiose produced during celluloysis is inhibitory to both exo- and endocellulases and, hence retards saccharification. The highly cellulytic fungus Trichoderma reesei and its mutant strains have been demonstrated to have potential for use in the practical saccharification of cellulosic materials. Although cellulase preparations derived from this fungus contain a very active cellulase complement of enzymes (i.e. both exo- and endo-cellulases) they are, nevertheless, deficient in ..beta..-glucosidase activity. Cellulase preparations of T. reesei containing higher levels of ..beta..-glucosidase activity can be obtained by supplementing with exogenous ..beta..-glucosidase preparations derived from another microorganism, which has been demonstrated to increase the rate and extent of saccharification of cellulose. Fungi belonging to the genus Aspergillus (e.g. A. niger and A. phoenicus) produce ..beta..-D-glucosidases in high yields which are compatible with T. reesei cellulases and promote saccharification of cellulose. Previous studies have shown that T. reesei cellulase preparations supplemented with Novozym 188 (Novo Industri A/S Denmark) were very effective in saccharifying pretreated sugarcane bagasse. The rather high cellulose conversions into glucose obtained in those studies promptedmore » an examination of the physicochemical and kinetic properties of the Novozym 188 ..beta..-glucosidase preparation which is described in this communication. Novo has provided some technical information on the pH and temperature properties of the enzyme. 15 references.« less

Absorbent structure containing individualized, crosslinked fibers

Abstract: Absorbent structures containing individualized, crosslinked fibers. The individualized, crosslinked fibers preferably have between about 0.5 mole % and about 3.5 mole % crosslinking agent, calculated on a cellulose anhydroglucose molar basis, reacted with the fibers in the form of intrafiber crosslink bonds, wherein the crosslinking agent is selected from the group consisting of C 2 -C 8 dialdehydes, C 2 -C 8 dialdehyde acid analogues having at least one aldehyde functionality, and oligomers of such C 2 -C 8 dialdehydes and dialdehyde acid analogues. More preferably, the crosslinking agent is glutaraldehyde, and between about 0.75 mole % and about 2.5 mole % crosslinking agent react to form the intrafiber crosslink bonds. Also preferably, the absorbent structures have actual dry densities greater than their corresponding equilibrium wet densities, and expand upon wetting. The absorbent structures may also contain hydrogel-forming material.

Chain modulus and intramolecular hydrogen bonding in native and regenerated cellulose fibers

Abstract: The respective values of the chain modulus of elasticity in cellulose I and II were used to determine the conformation of the cellulose chain in the native and regenerated fibers, and the number of intramolecular hydrogen bonds in the monomeric unit. -- AATA

Microcrystalline cellulose stabilizedemulsions

Abstract: Miorocrystalline cellulose stabilized emulsions (o/w) were evaluated by means of brightfield and polarized light microscopy, freeze-etch electron microscopy, droplet size analyses and rheologic measurements. These studies indicated that miorocrystalline cellulose (Avicel RC591 ) forms a network around emulsified oil droplets. This structure provides a mechanical barrier at the o/w interface which stabilizes the emulsion without the necessity for decreasing interfacial tension, as in conventional surfactant-stabilized emulsions. Rheologic studies indicated that emulsions containing Avicel RC591 had a considerable degree of thlxotropy which contributed to their stability. When Tween 80 was incorporated in this system, oil droplets coalesced indicating that the stability of the emulsion was affected adversely.

Biochemical changes associated with the ripening of hot pepper fruit

Abstract: Hot pepper (Capsicum annuum L. cv. Chooraehong) fruit underwent a respiratory climacteric during ripening. However, the rate of ethylene production was low, reaching a maximum of approximately 0.7 μl kg−1 h−1 at the climacteric peak when the surface color was 30 to 40% red. Ripening was accompanied by a loss of galactose and arabinose residues from the cell wall. The content of uronic acid and cellulose in the wall changed only slightly during ripening. The average molecular weight of a cell wall hemicellulosic fraction shifted progressively toward a lower molecular weight during ripening. Total β-galactosidase (EC 3.2.1.23) activity increased 50-fold from the immature green to the red ripe stage. No polygalacturonase (EC 3.2.1.15) activity was detected at any stage of ripeness. Thus, the loss of galactose and arabinose residues from the cell wall, as well as the observed modification of hemicelluloses during ripening, seem to be unrelated to active polygalacturonase. Soluble polyuronide content remained relatively constant at approximately 60 μg (g fresh weight)−1 as fruit ripended.

Dilute acid hydrolysis of wheat straw hemicellulose at moderate temperature: a simplified kinetic model.

Abstract: Wheat straw has been hydrolized with sulfuric acid at 34 and 90 degrees C. The treatment at 90 degrees C yields complete solubilization of hemicellulose to xylose and arabinose without significant amounts of furfural. The influence of acid concentration was studied and the kinetics of the acid-catalyzed hydrolysis has been modeled suggesting a two-consecutive reactions mechanism. This model is useful to explain the different behavior of the concentration of the two main sugars produced. The enhanced cellulose accessibility to enzymatic attack is also reported. 26 references.

Optical Resolution of β-Blockers by HPLC on Cellulose Triphenylcarbamate Derivatives

Abstract: Optical resolution of five β-adrenergic blocking agents (β-blockers) alprenolol, oxyprenolol, propranolol, pindolol, and atenolol was examined by HPLC on 13 chiral stationary phases composing of cellulose triphenylcarbamate derivatives. All β-blockers were completely resolved on a cellulose tris(3,5-dimethylphenylcarbamate) column.

Kinetic modeling of hardwood prehydrolysis. part iii. water and dilute acetic acid prehydrolysis of southern red oak

Abstract: The hemicelluloses in wood are more readily hydrolyzed than is cellulose. Because it is advantageous to process the hemicellulose sugars separately from the glucose obtained from the cellulose, most processes for utilizing wood as a source of chemicals and liquid fuels include a prehydrolysis step to remove the hemicelltdose prior to the main hydrolysis of the cellulose to glucose. Kinetic data are required to model the reactions that occur during prehydrolysis so that optimum conditions and product mixes can be predicted. Two promising prehydrolysis methods, the Iotech steam explosion process and the Stake process, are based on water prehydrolysis (autohydrolysis). The kinetics of water and of dilute (5%) acetic acid prehydrolysis of southern red oak wood over the temperature range of 170 to 240 C were investigated. Kinetic parameters were determined that permitted modeling not only of xylan removal from the wood but also of the occurrence of xylan oligosaccharides, free xylose, furfural, and further degradation products in the prehydrolyzate. At lower temperatures (approximately 170 to 200 C), xylan removal could be modeled as the sum of two parallel reactions (one for an easily hydrolyzed portion and one for a more resistant portion of xylan) using the equation derived in Part I. At the highest temperature studied (236.9 C), the removal of xylan from the wood was best modeled as a single reaction with a small fraction of the xylan being essentially nonreactive. The occurrence of xylan oligosaccharides, xylose, furfural, and further degradation products in the prehydrolyzate was modeled as consecutive, irreversible pseudo first-order reactions. A timelag associated with the depolymerization of the xylan oligosaccharides to xylose was accounted for in the model by allowing the apparent rate constant for the formation of xylose to increase exponentially with time to a maximum value. Increasing the temperature decreased the time required for the overall reactions to occur, increased the portion of xylan removed from the wood, and increased the yield of total anhydroxylose units (xylose + xylan oligosaccharides) that were recovered in the prehydrolyzate. Prehydrolysis with dilute acetic acid does not greatly affect the maximum yields of products in the prehydrolyzate over those observed with water prehydrolysis; however, the time to maximum yield decreased. The data presented in this report indicate that, at higher temperatures, water or dilute acetic acid prehydrolysis gives yields comparable to those for dilute sulfuric acid prehydrolysis at 170 C recently reported in the literature. Preliminary results with lignin isolated from the water and acetic acid prehydrolysis residues confirm recent reports that lignins of this type are useful as phenol substitutes in phenolformaldehyde adhesives.

Influence of Forage Phenolics on Ruminal Fibrolytic Bacteria and In Vitro Fiber Degradation

Abstract: In vitro cultures of ruminal microorganisms were used to determine the effect of cinnamic acid and vanillin on the digestibility of cellulose and xylan. Cinnamic acid and vanillin depressed in vitro dry matter disappearance of cellulose 14 and 49%, respectively, when rumen fluid was the inoculum. The number of viable Bacteroides succinogenes cells, the predominant cellulolytic organism, was threefold higher for fermentations which contained vanillin than for control fermentations. When xylan replaced cellulose as the substrate, a 14% decrease in the digestibility of xylan was observed with vanillin added; however, the number of viable xylanolytic bacteria cultured from the batch fermentation was 10-fold greater than that of control fermentations. The doubling time of B. succinogenes was increased from 2.32 to 2.58 h when vanillin was added to cellobiose medium, and absorbance was one-half that of controls after 18 h. The growth rate of Ruminococcus albus and Ruminococcus flavefaciens was inhibited more by p-coumaric acid than by vanillin, although no reduction of final absorbance was observed in their growth cycles. Vanillin, and to a lesser extent cinnamic acid, appeared to prevent the attachment of B. succinogenes cells to cellulose particles, but did not affect dissociation of cells from the particles. B. succinogenes, R. albus, R. flavefaciens, and Butyrivibrio fibrisolvens all modified the parent monomers cinnamic acid, p-coumaric acid, ferulic acid, and vanillin, with B. fibrisolvens causing the most extensive modification. These results suggest that phenolic monomers can inhibit digestibility of cellulose and xylan, possibly by influencing attachment of the fibrolytic microorganisms to fiber particles. The reduced bacterial attachment to structural carbohydrates in the presence of vanillin may generate more free-floating fibrolytic organisms, thus giving a deceptively higher viable count.

Effects of Differing Purified Cellulose, Pectin, and Hemicellulose Fiber Diets on Fecal Enzymes in 1,2-Dimethylhydrazine-induced Rat Colon Carcinogenesis

Abstract: The fecal microflora enzymes, β-glucuronidase and β-glucosidase, as well as fecal bacterial counts, were examined during colon carcinogenesis in rats administered parenteral 1,2-dimethylhydrazine and fed nutritionally equivalent diets free of fiber or containing one of three single sources of dietary fiber (cellulose, hemicellulose, and pectin). Whereas pectinfed animals had increased fecal β-glucuronidase activities, those fed cellulose and hemicellulose, two fibers protective in dimethylhydrazine colon neoplasia, had decreased activities. Although fecal bacterial counts were not significantly changed, similar differential changes in fecal β-glucosidase activity were noted: cellulose but not pectin or hemicellulose feeding was associated with reduced activity. Although cellulose fiber may cause differing physiological effects resulting in a reduction in colonic neoplasia development in this experimental animal model, decreased bacterial metabolic enzyme activation of carcinogens or cocarcinogens may lead to diminished exposure of colonic cells to exogenous or endogenous mutagens.

Specificity of cellulase and β-xylanase induction in Trichoderma reesei QM 9414

Abstract: Cellulose- and xylan-degrading enzymes of Trichoderma reesei QM 9414 induced by, sophorose, xylobiose, cellulose and xylan were analyzed by isoelectric focusing. The sophorose-induced enzyme system contained two types of endo-1,4-β-glucanases (EC 3.2.1.4), one specific for cellulose and the other non-specific, hydrolyzing both cellulose and xylan, and exo-1,4-β-glucanases (cellobiohydrolases I, EC 3.2.1.91), i.e. all types of glucanases that are produced during growth on cellulose. Specific endo-1,4-β-xylanases (EC 3.2.1.8) present in the cellulose-containing medium were less abundant in the sophorose-induced enzyme system. Xylobiose and xylan induced only specific endo-1,4-β-xylanases. It is concluded that syntheses of cellulases and β-xylanases in T. reesei QM 9414 are under separate control and that the non-specific endo-1,4-β-glucanases are constituents of the cellulose-degrading enzyme system.

Effects of pH on Lignin and Cellulose Degradation by Streptomyces viridosporus.

Abstract: Lignocellulose degradation by Streptomyces viridosporus results in the oxidative depolymerization of lignin and the production of a water-soluble lignin polymer, acid-precipitable polymeric lignin (APPL). The effects of the culture pH on lignin and cellulose metabolism and APPL production by S. viridosporus are reported. Dry, ground, hot-water-extracted corn (Zea mays) lignocellulose was autoclaved in 1-liter reagent bottles (5 g per bottle) and inoculated with 50-ml volumes of S. viridosporus cells suspended in buffers of specific pH (pH 6.0 to 9.2 at 0.4 pH unit intervals). Four replicates of inoculated cultures and of uninoculated controls at each pH were incubated as solid-state fermentations at 37°C. After 6 weeks of incubation the percent loss of lignocellulose, lignin, and carbohydrate and the amount of APPL produced were determined for each replicate. Optimal lignocellulose degradation, as shown by substrate weight loss, was observed in the pH range of 8.4 to 8.8. Only minor differences were seen in the Klason lignin, carbohydrate, protein, and ash contents of the APPLS produced by cultures at each pH. The effects of pH on the degradation of a spruce (Picea pungens) [14C-lignin]lignocellulose and a Douglas fir (Pseudotsuga menziesii) [14C-glucan]-lignocellulose were also determined at pH values between 6.5 and 9.5 (0.5 pH unit intervals). The incubations were carried out for 3 weeks at 37°C with bubbler-tube cultures. The percentage of initial 14C recovered as 14CO2, 14C-labeled water-soluble products, and [14C]APPL was then determined. The mineralization of lignin and cellulose to CO2 was optimal at pHs 6.5 and 7.0, respectively. However, the optimum for lignin and cellulose solubilization was pH 8.5, which correlated with the pH 8.5 optimum for APPL production. Overall, the data show that, whereas lignin mineralization is optimal at neutral to slightly acidic pHs, lignocellulose degradation with lignin solubilization and APPL production is promoted by alkaline pHs. These findings indicate that lignin-solubilizing actinomycetes may play an important role in the metabolism of lignin in neutral to alkaline soils in which ligninolytic fungi are not highly competitive.

Dilute acid pretreatment of biomass at high solids concentrations

Abstract: The dilute acid pretreatment of biomass (aspen wood and wheat straw) at high solids concentrations (up to 40 weight percent) has been investigated. It produces a concentrated monomeric soluble sugar stream (mainly xylose) with little degradation of the available sugars and a solid residue containing cellulose and lignin. The cellulose remaining in the residue from both aspen and straw pretreated at either 140 degrees or 160 degrees was highly digestible with commercial available enzymes. A somewhat higher acid consumption for wheat straw compared with that for aspen can be alleviated by a cation-removal step.

Determination of cellulose accessibility by differential scanning calorimetry

Abstract: The thermal behavior of various cellulose samples with different degrees of crystallinity as measured by X-ray diffraction techniques was studied with a differential scanning calorimeter (DSC). The broad endothermic peak which appears between 110 and 160°C is due to loss of absorbed (bound) water. Since a direct relationship was observed between the area of this peak and the crystallinity of the sample, a new procedure for estimating cellulose accessibility (which is related to crystallinity) was proposed and developed. DSC curves obtained on cellulose samples preconditioned at certain constant relative humidities were used to determine sample accessibilities by the proposed method. The accessibility values obtained by DSC showed excellent agreement with crystallinity values determined by more traditional techniques. Completely amorphous cellulose was obtained by anhydrous deacetylation of cellulose triacetate and was used as the standard amorphous cellulose material.

Alkaline peroxide treatment of agricultural byproducts

Abstract: Nonwoody lignocellulosic portions of plant fruits, roots, and tubers, such as sugar beet pulp, citrus pulp, seed hulls, and cereal bran are treated with hydrogen peroxide under alkaline conditions thereby delignifying the materials and rendering the cellulose and hemicellulose highly available for subsequent use. The products are characterized by enhanced water-binding capacity of the cellulose as indicated by high water swellability. The products are also nontoxic and thereby useful as carbohydrate sources in ruminant feeds, as microbial feedstocks, and as sources of dietary fiber for humans and other monogastrics.

Utilization of Xylan by Yeasts and Its Conversion to Ethanol by Pichia stipitis Strains.

Abstract: Yeasts able to grow on d-xylose were screened for the ability to hydrolyze xylan. Xylanase activity was found to be rare; a total of only 19 of more than 250 strains yielded a positive test result. The activity was localized largely in the genus Cryptococcus and in Pichia stipitis and its anamorph Candida shehatae. The ability to hydrolyze xylan was generally uncoupled from that to hydrolyze cellulose; only three of the xylan-positive strains also yielded a positive test for cellulolytic activity. Of the 19 xylanolytic strains, 2, P. stipitis CBS 5773 and CBS 5775, converted xylan into ethanol, with about 60% of a theoretical yield computed on the basis of the amount of d-xylose present originally that could be released by acid hydrolysis.

Pretreatment of wheat straw for fermentation to methane

Abstract: The effects of pretreating wheat straw with gamma-ray irradiation, ammonium hydroxide, and sodium hydroxide on methane yield, fermentation rate constant, and loss of feedstock constituents were evaluated using laboratory-scale batch fermentors. Results showed that methane yield increased as pretreatment alkali concentration increased, with the highest yield being 37% over untreated straw for the pretreatment consisting of sodium hydroxide dosage of 34 g OH(-)/kg volatile solids, at 90 degrees C for 1 h. Gamma-ray irradiation had no significant effect on methane yield. Alkaline pretreatment temperatures above 100 degrees C caused a decrease in methane yield. After more than 100 days of fermentation, all of the hemi-cellulose and more than 80% of the cellulose were degraded. The loss in cellulose and hemicellulose accounted for 100% of the volatile solids lost. No consistent effect of pretreatments on batch fermentation rates was noted. Semicontinuous fermentations of straw-manure mixtures confirmed the relative effectiveness of sodium and ammonium-hydroxide pretreatments.

Application of pretreatments for the isolation of bioactive actinomycetes from marine sediments

Abstract: Actinomycetes were isolated from marine sediments collected in Sandy Hook Bay, New Jersey. A variety of pretreatments, including heat and phenol, were employed to improve the recovery of these microorganisms. In addition, plating of sediment samples on chitin agar, and filtration through cellulose membrane filters were also utilized. These pretreatments eliminated or severely curtailed the growth of contaminating microorganisms thereby facilitating the isolation of actinomycetes. A total of 120 isolates was obtained, of which 19 displayed significant antimicrobial activity. Most of the activity was directed against gram-positive bacteria, but inhibition of gram-negative species and a yeast were also evident.

In vitro binding of steroid hormones by natural and purified fibers

Abstract: The in vitro binding of estrone, estradiol-17 beta, estriol, testosterone, dihydrotestosterone, and estrone-3-glucuronide by wheat, oat, and corn brans, oat hulls, cellulose, lignin, and cholestyramine resin was measured. The extent of steroid sequestration was characteristic and reproducible for each hormone. Cholestyramine bound an average of 90% of all the steroids tested, whereas cellulose bound the least (12%). Of the other substances tested, each bound the following percentage of unconjugated hormones: lignin, 87%; wheat and oat brans, 45% each; corn bran 44%; and oat hulls, 32%. The conjugated steroid was less likely to bind than the unconjugated steroids. Lignin appeared to be an important component in the interaction with steroid hormones. The results support the hydrophobic nature of adsorption and suggest that the components of fiber in diet should be considered separately when evaluating in vivo metabolic effects.

Enhanced cellulase production from Trichoderma reesei QM 9414 on physically treated wheat straw

Abstract: Trichoderma reesei QM 9414 was grown on wheat straw as the sole carbon source. The straw was pretreated by physical and chemical methods. The particle size of straw was less than 0.177 mm. Growth of T. reesei QM 9414 was maximal with alkali-pretreated straw whereas cellulase production was optimal when physically pretreated straw was used as substrate. Cellulase yields expressed as IU enzyme activity/g cellulose present in the cultures were considerably higher when alkali pretreatment of wheat straw was omitted. Cellulase yields of 666 IU/g cellulose for filter paper activity (FPA) are the highest described for cultures of T. reesei QM 9414 carried out in analogous conditions. Crystallinity index of the cellulose contained in wheat straw increased slightly after alkali pretreatment. This increase did not decrease cellulose accessibility to the fungus. Delignification of wheat straw was not necessary to achieve the best cellulase production.