Showing papers on "Cellulose published in 1983"

Wood: chemistry, ultrastructure, reactions.

Abstract: The anatomy and chemistry of wood are described in detail, and with extensive reference to the literature, under the following headings: Introduction; Structure and ultrastructure; Chemical composition and analysis of wood; Cellulose; Polyoses (hemicelluloses); Lignin; Extractives; Distribution of the components within the wood cell wall; Constituents of bark; Reactions in acidic medium; Reactions in alkaline medium; Influence of temperature; Degradation by light and ionizing rays; Microbial and enzymatic degradation; Aging and fossilization; Pulping processes; Derivatives of cellulose; and Utilization of wood and wood components for chemicals and energy. -- AATA

Microfibrillated cellulose, a new cellulose product: properties, uses, and commercial potential

Abstract: A new form of cellulose, which is expanded to a smooth gel when dispersed in polar liquids, is produced by a unique, rapid, physical treatment of wood cellulose pulps. A 2% suspension of microfibrillated cellulose (MFC) in water has thixotropic viscosity properties and is a stable gel on storage, or when subjected to freeze-thaw cycles. At this concentration, MFC is an excellent suspending medium for other solids and an emulsifying base for organic liquids. In laboratory tests, microfibrillated cellulose has been demonstrated to have wide utility in the preparation of foods such as low-calorie whipped toppings, cake frostings, salad dressings, gravies, and sauces. At 0.3% cellulose concentration in ground meats, MFC helps retain juices during cooking. Tests were also conducted in formulating paints, emulsions, and cosmetics and in the use of MFC as a binder for nonwoven textiles and as a mineral suspending agent. From economic studies, it is estimated that a 2% MFC dispersion can be produced for about 1.5 cents/lb, total cost. 6 references, 9 figures, 2 tables.

Microfibrillated cellulose: morphology and accessibility

Abstract: Microfibrillated cellulose (MFC) is prepared by subjecting dilute slurries of cellulose fibers to repeated high-pressure homogenizing action. A highly microfibrillated product will have a gel-like appearance at 2% concentration in water. Such gels have pseudoplastic viscosity properties and are very fluid when stirred at high shear rate. The relative viscosity of 2% MFC dispersions may be used as a measure of the degree of homogenization or microfibrillation of a given wood cellulose pulp. The water retention value of an MFC product can also be used as an indicator for degree of homogenization. Structurally, MFC appears to be a web of interconnected fibrils and microfibrils, the latter having diameters in the range 10-100 nm as observed in scanning and transmission electron micrographs. Chemical studies have revealed that MFC is only moderately degraded, while being greatly expanded in surface area. The accessibility of cellulose in MFC is only moderately degraded, while being greatly expanded in surface area. The accessibility of cellulose in MFC toward chemical reagents is greatly increased. Higher reactivity was demonstrated in dilute cupriethylenediamine solubility, triphenylmethylation, acetylation, periodate oxidation, and mineral acid and cellulase enzyme hydrolysis rates. 16 references, 8 figures, 7 tables.

Role of bacterial cellulose fibrils in Agrobacterium tumefaciens infection.

Abstract: During the attachment of Agrobacterium tumefaciens to carrot tissue culture cells, the bacteria synthesize cellulose fibrils. We examined the role of these cellulose fibrils in the attachment process by determining the properties of bacterial mutants unable to synthesize cellulose. Such cellulose-minus bacteria attached to the carrot cell surface, but, in contrast to the parent strain, with which larger clusters of bacteria were seen on the plant cell, cellulose-minus mutant bacteria were attached individually to the plant cell surface. The wild-type bacteria became surrounded by fibrils within 2 h after attachment. No fibrils were seen with the cellulose-minus mutants. Prolonged incubation of wild-type A. tumefaciens with carrot cells resulted in the formation of large aggregates of bacteria, bacterial fibrils, and carrot cells. No such aggregates were formed after the incubation of carrot cells with cellulose-minus A. tumefaciens. The absence of cellulose fibrils also caused an alteration in the kinetics of bacterial attachment to carrot cells. Cellulose synthesis was not required for bacterial virulence; the cellulose-minus mutants were all virulent. However, the ability of the parent bacterial strain to produce tumors was unaffected by washing the inoculation site with water, whereas the ability of the cellulose-minus mutants to form tumors was much reduced by washing the inoculation site with water. Thus, a major role of the cellulose fibrils synthesized by A. tumefaciens appears to be anchoring the bacteria to the host cells, thereby aiding the production of tumors.

Shaped cellulose article prepared from a solution containing cellulose dissolved in a tertiary amine N-oxide solvent and a process for making the article

Abstract: A solution containing cellulose dissolved in a tertiary amine N-oxide solvent containing a nonsolvent for cellulose such as water is shaped by extrusion or other shaping process to form a shaped cellulose fiber, rod, plate, tubing or film. The extruded shaped article is stretched in air while still a solution to impart improved physical properties thereto and the cellulose is precipitated from the shaped solution to set the properties without additional drawing. The solution may be prepared by dissolving cellulose in the tertiary amine N-oxide solvent in the barrel of an extrusion apparatus, extending the solution, orienting by stretching the resulting product in air while still a solution and then precipitating the cellulose from the shaped article before significant degradation of the cellulose. The cellulose and tertiary amine N-oxide may be ground to substantially the same particle size before charging the extruder barrel. The tertiary amine N-oxide is recovered and recycled to avoid environmental pollution problems. The resulting cellulose fibers or films can be used to make fabrics, wrapping or packaging materials or non-woven products.

Bioconversion of waste cellulose by using an attrition bioreactor.

Abstract: A new type of reactor, an attrition bioreactor, was tested to achieve a higher rate and extent of enzymatic saccharification of cellulose than is possible with conventional methods. The reactor consisted of a jacketted stainless-steel vessel with shaft, stirrer, and milling media, which combined the effect of the mechanical action of wet milling with cellulose hydrolysis. The substrates tested were newsprint and white-pine heartwood. The performance of the reactor was excellent. The extent and rate of enzymatic hydrolysis could be markedly improved over other methods. The power consumption of the attrition bioreactor was also measured. The cellulase enzyme deactivation during attrition milling was not significant.

Effects of reactor severity on the gas-phase pyrolysis of cellulose- and kraft lignin-derived volatile matter

Abstract: Yields of permanent gases evolved by the gas-phase pyrolysis of cellulose- and lignin-derived voltatile matter cannot be correlated with a commonly used kinetic severity function. Instead, engineers explained the dependence of gas yields on temperature and residence time by a global mechanism composed of two competing reactions. The first creates permanent gases by cracking the volatile matter, whereas the second creates refractory condensable materials. For cellulose, the cracking reaction has an apparent activation energy of 49 kcal/g-mol, and the competing reaction 15 kcal/g-mol. The gas-phase cracking of cellulosic volatile matter involves competition between the dehydration (resulting in methane and ethylene formation) and decarboxylation reactions; the fraction of carbon atoms dedicated to carbon monoxide formation by the cracking reaction is not influenced by temperature. For lignin, competition exists between ethylene and carbon dioxide formation; the fraction of carbon atoms dedicated to carbon monoxide and methane formation is not influenced by temperature.

Adsorption of cellulase from Trichoderma viride on cellulose.

Abstract: The adsorption of cellulase from Trichoderma viride (Meicelase CEP) on the surface of pure cellulose was studied. The adsorption was found to obey apparently the Langmuir isotherm. From the data concering the effects of temperature and the crystallinity of cellulose on the Langmuir adsorption parameters, the characteristics of the adsorption of the individual cellulase components, namely CMCase (endoglucanase) and Avicelase (exoglucanase), were discussed. While beta-glucosidase also adsorbed on the surface of cellulose at 5 degrees C, it did not at 50 degrees C.

Bioconversion of hemicellulose: aspects of hemicellulase production by Trichoderma reesei QM 9414 and enzymic saccharification of hemicellulose.

Abstract: The growth of Trichoderma reesei QM9414 in shake flasks at 28 degrees C on hemicellulose substrates and bagasse resulted in rather low yields of hemicellulolytic enzymes (1.0-1.5 units/mL xylanase and 0.05-0.08 units/mL beta-xylosidase). The influence of pH on the synthesis of beta-xylosidase was greater than on the synthesis of xylanase. Both xylanase and beta-xylosidase showed optimal activity at pH 4-5 and 55-60 degrees C. Xylanase was stable at pH 2-10 but was heat labile and totally inactivated after 1 h at 65 degrees C. Enzyme stability towards heat could be increased in the presence of bovine serum albumin. The beta-xylosidase was more tolerant to heat, but stable over a pH range 2.5-6.0. The D-xylose inhibited both enzymes in a competitive manner. Hemicellulose (heteroxylan) was degraded to the extent of 30-40%within 24 h. The degree of hydrolysis decreased as the substrate concentration increased and increased with increased amounts of enzyme. Multiple enzyme doses resulted in increased saccharification in reduced times. The degree of hydrolysis was influenced by the amount of beta-xylosidase present in the hemicellulolytic enzyme preparation. The -;xylosidase was demonstrated to play an important role in the overall conversion of heteroxylan into xylose that is analogous to the role of beta-glucosidase in the saccharification of cellulose by cellulases.

Degradation of 14C-labelled poplar wood lignin by selected white-rot fungi

Abstract: Of eight white-rot fungi examined, seven fungi grew on nitrogen-limited poplar wood meal medium and degraded 14C-lignin in wood meal to 14CO2. Increased oxygen enhanced both the rate and extent of degradation. However, whereas Pleurotus ostreatus, Pycnoporus cinnabarinus 115 and Pycnoporus cinnabarinus A-360 degraded 12–17% of 14C-(U)-lignin of poplar wood to 14CO2 also in an air atmosphere, Sporotrichum pulverulentum, Phlebia radiata 79 and Phanerochaete sordida 37 degraded only 1–5% under these conditions. Addition of cellulose and glucose to the poplar wood medium stimulated degradation of 14C-(RING)-lignin of poplar wood by Phlebia radiata 79 but repressed degradation by Polyporus versicolor and Pleurotus ostreatus. Cellulose added to the wood meal medium had no effect on the degradation of lignin by Phanerochaete sordida 37 and Sporotrichum pulverulentum but glucose slightly repressed lignin degradation by these fungi. Those white-rot fungi which were considered as preferentially lignin attacking fungi could degrade 14C-(RING)-lignin of poplar wood efficiently under 100% oxygen. They did not require an extra energy source in addition to wood meal polysaccharides for rapid ring cleavage and they degraded up to 50–60% of the 14C-lignin to 14CO2 in 6–7 weeks at a maximum rate of 3–4% per day.

Effect of soluble carbohydrates on digestion of cellulose by pure cultures of rumen bacteria. [Ruminococcus flavefaciens, R. albus, Bacteroides succinogenes]

Abstract: The rate of cellulose digestion in the presence of either glucose or cellobiose was studied for the three predominant species of cellulolytic rumen bacteria: Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes. When a soluble carbohydrate was added to cellulose broth, the lag phase of cellulose digestion was shortened. Presumably, this was due to greater numbers of bacteria, because increasing the size of the inoculum had a similar effect. Cellulose digestion occurred simultaneously with utilization of the soluble carbohydrate. The rate of cellulose digestion slowed markedly for B. succinogenes and R. flavefaciens and slowed less for R. albus after the cellobiose or glucose had been utilized, and was accompanied by a decrease in pH. Both the rate and the extent of cellulose digestion were partially inhibited when the initial pH of the medium was 6.3 or below. R. albus appeared to be less affected by a low-pH medium than were B. succinogenes and R. flavefaciens. When a soluble carbohydrate was added to the fermentation during the maximum-rate phase of cellulose digestion, the rate of cellulose digestion was not affected until after the soluble carbohydrate had been depleted and the pH had decreased markedly. Prolonged exposure of the bacteria to a lowmore » pH had little if any effect on their subsequent ability to digest cellulose. Cellulase activity of intact bacterial cells appeared to be constitutive in nature for these three species of rumen bacteria. 30 references.« less

Kinetic studies of enzymatic hydrolysis of insoluble cellulose: (II). Analysis of extended hydrolysis times.

Abstract: The kinetics of enzymatic hydrolysis of pure insoluble cellulose by means of unpurified culture filtrate of Trichoderma reesei was studied, emphasizing the kinetic characteristics associated with the extended hydrolysis times. The changes in the hydrolysis rate and extent of soluble protein adsorption during the progress of reaction, either apparent or intrinsic, were investigated. The hydrolysis rate declined drastically during the initial hours of hydrolysis. The factors causing the reduction in the hydrolysis rate were examined; these include the transformation of cellulose into a less digestible form and product inhibition. The structural transformation can be partially explained by changes in the crystallinity index and surface area. The product inhibition was caused by the deactivation of the adsorbed soluble protein by the products, which essentially represents the so-called "un-competitive" inhibition. The kinetics of beta-glucosidase were also studied. The result has shown that the action of beta-glucosidase is competitively inhibited by glucose. It has been found that the integrated form of the initial rate expression cannot be used in predicting the progress of reaction because the digestibility of cellulose changes drastically as the hydrolysis proceeds, and that the rate expression for enzymatic hydrolysis of cellulose cannot be simplified or approximated by resorting to the pseudo-steady-state assumption. A mechanistic kinetic model of cellulose hydrolysis should include the following major influencing factors: (1)mode of action of enzyme, (2) structure of cellulose, and (3) mode of interaction between the enzyme and cellulose molecules.

Pretreatment of wheat straw by white-rot fungi for enzymatic saccharification of cellulose

Abstract: SummaryOf 19 white-rot fungi tested, Pleurotus ostreatus, Pleurotus sp. 535, Pycnoporus cinnabarinus 115 and Ischnoderma benzoinum 108 increased the susceptibility of straw to enzymic saccharification, thus indicating that these organisms degraded or modified the lignin component. After pretreatment cultivation with Pycnoporus cinnabarinus 115, as much as 54.6% of the residue was converted to reducing sugars in the enzymic saccharification process. Phanerochaete sordida 37, Phlebia radiata 79 and two unidentified fungi also gave better results than Polyporus versicolor, a non-selective reference fungus. After 5 weeks pretreatment with Pleurotus ostreatus, 35% of the original straw was convertable to reducing sugars, 74% of which was glucose; compared with this, only 12% of the untreated control straw was convertable to reducing sugars, 42% of which was glucose. After an alkali pretreatment (2% NaOH, 0.4 g NaOH/g straw, 10 min at 115°C) enzymic saccharification converted 41% of the straw to reducing sugars, of which only 50% was glucose. In the best cases the efficiency of biological pretreatment was comparable with that of alkali treatment, but resulted in a higher proportion of glucose in the hydrolysates. Pretreatment by the fungi Phanerochaete sordida 37 and Pycnoporus cinnabarinus 115 in an oxygen atmosphere reduced the treatment time by approximately 1 week. However, the economic feasibility of a non-optimized biological pretreatment process is still poor due to the long cultivation times required.

Effect of soluble carbohydrates on digestion of cellulose by pure cultures of rumen bacteria.

Abstract: The rate of cellulose digestion in the presence of either glucose or cellobiose was studied for the three predominant species of cellulolytic rumen bacteria: Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes. When a soluble carbohydrate was added to cellulose broth, the lag phase of cellulose digestion was shortened. Presumably, this was due to greater numbers of bacteria, because increasing the size of the inoculum had a similar effect. Cellulose digestion occurred simultaneously with utilization of the soluble carbohydrate. The rate of cellulose digestion slowed markedly for B. succinogenes and R. flavefaciens and slowed less for R. albus after the cellobiose or glucose had been utilized, and was accompanied by a decrease in pH. Both the rate and the extent of cellulose digestion were partially inhibited when the initial pH of the medium was 6.3 or below. R. albus appeared to be less affected by a low-pH medium than were B. succinogenes and R. flavefaciens. When a soluble carbohydrate was added to the fermentation during the maximum-rate phase of cellulose digestion, the rate of cellulose digestion was not affected until after the soluble carbohydrate had been depleted and the pH had decreased markedly. Prolonged exposure of the bacteria to a low pH had little if any effect on their subsequent ability to digest cellulose. Cellulase activity of intact bacterial cells appeared to be constitutive in nature for these three species of rumen bacteria.

Biomass pretreatment with water and high-pressure oxygen. The wet-oxidation process

Abstract: A biomass pretreatment process called wet oxidation that utilized water, oxygen (240-480 psi), and temperatures above 120 degrees C was applied to loblolly pine, black oak, and a mixture of low-grade hardwoods. The process was found to be effective for fractionating the hemicellulose, lignin, and cellulose components of wood. Acid hydrolysis studies showed that the wet oxidation also enhanced the rate at which cellulose was hydrolyzed by acids to glucose. (Refs. 28).

Chemical modification of wood

Abstract: After millions of years of evolution, wood was designed to perform in a wet environment, and nature is programmed to recycle it, in a timely way, back to the basic building blocks of carbon dioxide and water through biological, thermal, aqueous, photochemical, chemical, and mechanical degradation. The properties of wood are, for the most part, a result of the chemistry of its cell wall components. The polysaccharides (cellulose and hemicelluloses) are mainly responsible for (i) moisture uptake and release in changing environments that result in changes in wood volume (dimensional instability), (ii) recognition mechanisms for biological degradation (attack by fungi, termites, etc.), (iii) thermal instability (pyrolysis and burning), (iv) chemical degradation (by acids and bases), and, to some degree, (v) degradation due to ultraviolet radiation (weathering, lignin degradation).

Solid-state 13C-NMR study of conformations of oligosaccharides and cellulose: Conformation of CH2OH group about the exo-cyclic C-C bond

Abstract: CP/DD/MAS 13C NMR spectra have been obtained for different monosaccharides, oligosaccharides, and cellulose. It has been found that a simple linear relationship exists between the chemical shift of the CH2OH carbon and the torsion angle χ about the exo-cyclic C-C bond. The chemical shifts fall into three groups of 60–62.6 ppm, 62.5–64.5 ppm, and 65.5–66.5 ppm, which are related to gauche-gauche, gauche-trans, and trans-gauche conformations, respectively. On the basis of these results the conformation of the CH2OH carbon of cellulose is also discussed.

Structural properties of cellulose and cellulase reaction mechanism

Abstract: The effects of structural properties and their changes during cellulose hydrolysis on the enzymatic hydrolysis rate have been studied from the reaction mechanism point of view. Important findings are the following: (1) The crystallinity index (CrI) of partially crystalline cellulose increases as the hydrolysis reaction proceeds, and a significant slowing down of the reaction rate during the enzymatic hydrolysis is, in large part, attributable to this structural change of cellulose substrate. (2) The crystallinity of completely disordered cellulose, like phosphoric-acid-treated cellulose, does not change significantly, and a relatively high hydrolysis rate is maintained during hydrolysis. (3) The specific surface area (SSA) of partially crystalline cellulose decreases significantly during enzymatic hydrolysis while the change in SSA of regenerated cellulose is found to be negligible. (4) The value of degree of polymerization (DP) of highly ordered crystalline cellulose remains practically constant whereas the change in DP of disordered regenerated cellulose is found to be very significant. (5) Combination of these structural effects as well as cellulase adsorption, product inhibition, and cellulase deactivation all have important influence on the rate of cellulase reaction during cellulose hydrolysis. More experimental evidence for a two-phase model, which is based on degradation of cellulose by simultaneous actions of cellulase complex on the crystalline and amorphous phases, has been obtained. Based on experimental results from this study and other results accumulated, the mode of cellulase action and a possible reaction mechanism are proposed.

Enzymic saccharification of sugarcane bagasse pretreated by autohydrolysis-steam explosion.

Abstract: Pretreatment of bagasse by autohydrolysis at 200 degrees C for 4 min and explosive defibration resulted in the solubilization of 90% of the hemicellulose (a heteroxylan) and in the production of a pulp that was highly susceptible to hydrolysis by cellulases from Trichoderma reesei C-30 and QM 9414, and by a comercial preparation, Meicelase. Saccharification yields of 50% resulted after 24 h at 50 degrees C (pH 5.0) in enzymic digests containing 10% (w/v) bagasse pulps and 20 filter paper cellulase units (FPU). Saccharifications could be increased to more than 80% at 24 h by the addition of exogenous beta-glucosidase from Aspergillus niger. The crystallinity of cellulose in bagasse remained unchanged following autohydrolysis-explosion and did not appear to hinder the rate or extent of hydrolysis of cellulose. Autohydrolysis-exploded pulps extracted with alkali or ethanol to remove lignin resulted in lowere conversions of cellulose (28-36% after 25 h) than unextracted pulps. Alkali extracted pulps arising from autohydrolysis times of more than 10 min at 200 degrees C were less susceptible to enzymic hydrolysis than unextracted pulps and alkali-extracted pulps arising from short autohydrolysis times (e.g., 2 min at 200 degrees C). Autohydrolysis-explosion was as effective a pretreatment method as 0.25M NaOH (70 degrees C/2 h) both yielded pulps that resulted in high cellulose conversions with T. reesei cellulase preparations and Meicelase. Supplementation of T. reesei C-30 cellulose preparations with A. niger beta-glucosidases was effective in promoting the conversion of cellulose into glucose. A ration of FPU to beta-glucosidase of 1:1.25 was the minimum requirement to achieve more than 80% conversion of cellulose into glucose within 24 h. Other factors which influenced the extent of saccharification of autohydrolysis-exploded bagasse pulps were the enzyme-substrate ratio, the substrate concentration, and the saccharification mode.

Hydrothermolysis -- a new process for the utilization of biomass.

Abstract: In the present paper a hydrothermolysis apparatus is described. The reaction vessel is of the percolator type with a volume of 560 cm3 and permits the hydrolysis of biomass materials up to 100 g. The optimum degradation conditions of pure cellulose (filter paper) were determined in dependence on temperature, flow rate of the eluting water and influence of stirring on the reaction mixture. Up to 52% glucose can be obtained by hydrolysing cellulose with pure water at 265°C at a flow rate of 12 cm3/min.

Redispersible microfibrillated cellulose

Abstract: Redispersible microfibrillated cellulose is prepared by the addition to a liquid dispersion of the microfibrillated cellulose, an additive compound capable of substantially inhibiting hydrogen bonding between the cellulose fibrils. The microfibrillated cellulose, upon drying, is characterized by having a viscosity when redispersed in water of at least 50% of the viscosity of an equivalent concentration of the original dispersion.

Removal of Uranium(VI) from Solution by Fungal Biomass and Fungal Wall-Related Biopolymers.

Abstract: Penicillium digitatum mycelium can accumulate uranium from aqueous solutions of uranyl chloride. Azide present during the uptake tests does not inhibit the process. Killing the fungal biomass in boiling water or by treatment with alcohols, dimethyl sulfoxide, or potassium hydroxide increases the uptake capability to about 10,000 parts per million (dry weight). Formaldehyde killing does not enhance the uranium uptake. The inference that wall-binding sites were involved led to the testing of uranium uptake by chitin, cellulose, and cellulose derivatives in microcolumns. All were active, especially chitin.

The nature of inhibitory materials present in pretreated lignocellulosic substrates which inhibit the enzymatic hydrolysis of cellulose

Abstract: Wheat straw and aspen wood chips were pretreated by steam explosion and the various fractions were assayed for the presence of materials which inhibited the enzymatic hydrolysis of the cellulose component of the lignocellulosic substrates to glucose. The inhibitory material could be removed from all of the fractions by simple water extraction. The inhibitory substances were shown to primarily inhibit the B-glucosidase component of the cellulase complex of Trichoderma harzianum E58. The furan derivatives, furfural and hydroxymethyl furfural were not inhibitory at concentrations normally found in steam exploded lignocellulosic substrates.