Cellulose synthesized by Acetobacter xylinum in the presence of plant cell wall polysaccharides

Acetobacter xylinum was cultured in Schramm–Hestrin (SH) medium containing glucuronoxylan (xylan medium) or pectin (pectin medium). Loose bundles of cellulose microfibrils were formed in the xylan medium. In contrast the cellulose ribbons formed in the pectin medium were the same as those normally formed in SH medium.The periodic acidthiocarbohydrazidesilver proteinate method indicated that positive reacted substances located along cellulose microfibrils formed in both mediums. Freeze-fracture and deepetching electron microscopy also revealed that polysaccharides exist around cellulose microfibrils. X-ray diffractometry and Fourier Transform In-frared spectroscopy demonstrated that the addition of xylan induced a change in the ratio of cellulose I and I. Electron diffraction analysis revealed that xylan discontinuously affected the crystalline structure of cellulose microfibrils. Pectin did not have this effect. Glucuronoxylan in the medium prevented the assembly of cellulose     

Cellulose Synthesized by Acetobacter Xylinum in the Presence of Acetyl Glucomannan

Acetobacter xylinum was cultured in Hestrin-Schramm medium (control medium) and Hestrin-Schramm medium containing acetyl glucomannan (mannan medium). Loose bundles of the cellulose microfibrils are formed in the mannan medium in contrast to the normal ribbons being produced in the control medium. Rapid-freeze and substitution method followed by metal-shadowing revealed the droplet-like structures around the microfibril synthesized in the mannan medium. The cellulose synthesized in the mannan medium was stained heavily by the periodic acid-thiocarbohydrazide-silver proteinate (PATAg) method, while the cellulose synthesized in the control medium was not stained. X-ray diffractometry and FT-IR spectroscopy indicated that the addition of mannan induced a change in the crystal structure from the algal-bacterial type to the cotton-ramie type. Thus the presence of acetyl glucomannan in the medium prevents the assembly of cellulose microfibrils and changes the crystal structure of cellulose.     

Carbohydrates ofSymphytum asperum

It has been shown that the carbohydrates ofSymphytum asperum L. — a promising fodder plant — include water-soluble polysaccharides, pectin substances, protopectin, hemicelluloses, a glucomannan, and cellulose. The quantitative amounts of the polysaccharide fractions in the raw material have been established and their characteristics are given. The protopectins of the leaves and stems ofSymphytum asperum L. have been characterized. Their macromolecules are based on a fragment constructed of D-galacturonic acid residues linked by -glycosidic bonds.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–20, January–February, 1984.     

Hydrolyzability of mannan after adsorption on cellulose

During the pretreatment of lignocellulosic materials, the dissolved mannan would re-adsorb on cellulose, and then inhibited the cellulose hydrolysis by cellulases. However, the adsorption of mannan on cellulose and hydrolyzability of mannan adsorbed on cellulose were not so clear. In this work, the adsorption behavior of mannans on cellulose and the hydrolysis of adsorbed mannan by mannanase were investigated. Adsorption of 1, 4-β-D-mannan (mannan), Konjac glucomannan (GM), and Carob galactomannan (GalM) on Avicel and corn stover (CS) was increased with mannan loading. The adsorbed amount of mannan (94.4 mg/g Avicel and 85.1 mg/g CS) on cellulosic substrates at the mannan concentration of 5 mg/mL was significantly higher (p < 0.05) than that of GM (65.7 mg/g Avicel and 63.7 mg/g CS) and GalM (44.3 mg/g Avicel and 48.7 mg/g CS). Furthermore, the NMR spectra and molecular weight analysis showed that mannan with less side groups and low molecular weight might increase the adsorption. Mannan, GM, and GalM adsorbed on Avicel and CS, which was used as Avicel/CS -mannan/GM/GalM complex, could be hydrolyzed by mannanase, and the hydrolyzability of Avicel-mannan/GalM complexes was stronger than that of Avicel-GM complex. Similarly, the reducing sugars increased by 23.2 and 54.2 % for Avicel-mannan and Avicel-GalM complexes after 48 h hydrolysis by cellulase and mannanase, respectively. The results suggested that the addition of mannanase could hydrolyze the mannan adsorbed on cellulose and potentially improved hydrolysis efficiency of cellulose in lignocelluloses. Additionally, the mannanase supplementation could be extended to the removal of mannan on pulp by mannanase and finally affecting the dissolving pulps and paper quality.     

羟丙基甲基纤维素与魔芋葡甘聚糖复配体系相互作用的研究

采用黏度测试、振荡测试以及动态力学分析方法,以结构典型的羟烷基烷基纤维素醚———羟丙基甲基纤维素(HPMC)与魔芋葡甘聚糖(KGM)混合体系为研究对象,通过对两种天然多糖混合水溶液表观黏度、流变性及溶液动态力学参数的变化,分析了结构差异性天然多糖大分子间相互作用的机理并建立分子模型.实验表明,HPMC-KGM复配后,KGM分子链上未被取代的甘露糖单元与HPMC分子链上憎水性基团通过疏水作用形成弱交联的疏水缔合区域,而形成以HPMC分子为骨架并与KGM分子相联结的结构.HPMC与KGM按质量比3∶1到1∶1比例范围内复配效应最为明显.通过疏水缔合作用,缓解KGM分子在高温条件下的降解,还对HPMC的热凝胶化作用起到延缓效果.     

Influence of hemicelluloses on the aggregation patterns of bacterial cellulose

Cellulose from the bacteriumAcetobacter xylinum was used as a model system for investigating the influence of other cell wall polysaccharides on the aggregation of cellulose. The patterns of aggregation of the bacterial cellulose were modified when the cellulose was produced in the presence of hemicellulose-like saccharides. The celluloses were found to be more like the I-type found in higher plant celluloses than the I-type in the control bacterial celluloses. The effects of isolation procedures on structure were also explored. It was found that the structures of isolated celluloses were influenced by the procedures used in isolation.Formerly The Institute of Paper Chemistry, Appleton, WI, USA.Retired     

Structure and Function of a Multidomain Alkaline Xylanase from Alkaliphilic Bacillus Sp. Strain 41M-1

Xylanase is an enzyme that catalyzes the hydrolysis of xylan, a -1,4-linked xylose polymer. Alkaliphilic Bacillus sp. strain 41M-1 secretes a xylanase (xylanase J) that has an alkaline pH optimum. Xylanase J is a multidomain enzyme and consists of two functional domains: a family 11/G catalytic domain and a non-catalytic xylan-binding domain. The xylan-binding domain bound to xylan and enhanced catalytic activity of the adjacent catalytic domain. Mutational analyses revealed some amino acid residues that contribute to catalytic activity, alkaliphily and xylan-binding activity of xylanase J.     

The impact of cellulose structure on binding interactions with hemicellulose and pectin

Four cellulose substrates including highly crystalline cellulose nanowhiskers (CNWs) from Gluconacetobacter xylinus (cellulose Iα) or cotton (cellulose Iβ) and amorphous cellulose derived from CNWs (phosphoric acid swollen cellulose nanowhiskers, PASCNWs) were used to explore the interaction between cellulose and well-defined xyloglucan, xylan, arabinogalactan and pectin. The binding behavior was characterized by adsorption isotherm and Langmuir models. The maximum adsorption and the binding constant of xyloglucan, xylan and pectin to any CNWs were always higher than to PASCNWs derived from the same source. The binding affinity of xyloglucan, xylan and pectin to G. xylinus cellulose was generally higher than to cotton cellulose, showing that binding interactions depended on the biological origin of cellulose and associated differences in its structure. The surface area, porosity, crystal plane and degree of order of cellulose substrate may all impact the interactions.     

On the accessibility and structure of xylan in birch kraft pulp

The structure of -(14)-xylan, both in isolated form and as a component of bleached birch kraft pulp, was studied employing CP/MAS ¹³C NMR spectroscopy. Bleached birch kraft pulp was treated with xylanases or alkali in order to distinguish between accessible and inaccessible xylan. In xylan which was alkali-extracted from bleached birch kraft pulp, the relative contents of xylose and 4-O-methylglucuronic acid were 99.4 and 0.6 weight %, respectively, and the degree of polymerization was 70. The supermolecular structure of xylan is very sensitive to the surrounding environment. All extracted xylan chains were accessible to water and methanol and the solvent molecules easily exchanged. In bleached birch kraft pulp, cellulose fibrils interact with xylan chains, causing these to adopt a conformation similar to one of the configurations observed for dry xylan. In birch pulp, about 1/3 of the xylan was found to be accessible to digestion by xylanases or extraction with 5% w/w potassium hydroxide (aq). A signal at 81.7ppm in the C-4 region of the CP/MAS ¹³C NMR spectrum of bleached birch kraft pulp originated from xylan at the accessible fibril surfaces. A portion of a broad signal at 83.5ppm reflected inaccessible xylan, which is probably present as co-aggregates with cellulose fibril aggregates.     

Water-Soluble Polysaccharides from Narcissus poeticus and Their Biological Activity

A homogeneous native acetylated glucomannan of molecular weight 32000 was isolated from bulbs of N. poeticus. A linear chain polymer consisting of -14-bound D-manno- and D-glucopyranoses was found using periodate and chromic oxidation and methylation. The glucomannan has low toxicity and exhibits distinct hypolipidemic activity.     

Thermoplastic Xylan Derivatives with Propylene Oxide

Polymeric xylan can be reacted with propylene oxide (PO) in aqueous alkali homogeneously. Since xylan is isolated from biomass in aqueous alkaline solution, an in-line modification with PO as part of the isolation protocol, is most practical. Hydroxypropyl xylan (HPX) is a low molecular weight, branched, water-soluble polysaccharide with low intrinsic viscosity and thermoplasticity. Following peracetylation of HPX in formamide solution, water-insoluble acetoxypropyl xylan (APX) is formed that is also thermoplastic but no longer water soluble. The glass transition temperature (T _g) of APX varies in relation to degree of substitution with hydroxypropyl groups (DS_PO), and this is found to decline from 160 to 70°C as DS_PO rises from 0.2 to 2.0. At a temperature above the T _g of HPX a molecular reorganization is noted, and a faint transition due to melting (T _m) is observed at 205°C. HPX thermally degrades with a weight loss maximum at 317°C, or approximately 60°C below that of a corresponding cellulose derivative. HPX forms clear films when solvent cast from aqueous solution. Films are higher in ultimate tensile strength and lower in toughness than corresponding cellulose derivative films. The properties of HPX and APX derivatives qualify this material as a potential biodegradable and thermoplastic additive to melt-processed plastics. Blend characteristics with polystyrene reveal a shear-thinning effect in melt and a plasticization effect in solid state.     

Bildung von α-Mannosidase durch Arthrobacter

The production of yeast cell wall mannan degrading -mannosidase was studied in shake flask experiments as well as in a highly instrumented, computer-coupled bioreactor. The enzyme is predominantly excreted into the culture liquid upon submerged cultivation on yeast mannan. Only low activities were detected with mannose or glucose as carbon source whereas the enzyme formation was totally repressed by glycerol. The amount of enzyme produced is proportional to the microbial biomass formed.Carbon-unlimited cultivation on mannose, the primary product of enzymic digestion, resulted in a specific growth rate of 0.10h^–1, a specific oxygen uptake rate ·h and a respiratory quotient ofRQ=1.0. Addition of yeast mannan (0.5%) to nutrient-depleted bacterial cells resulted in an almost complete utilization of this substrate, with 55% of substrate carbon being converted to biomass and 37% to carbon dioxide. The yield coefficient on mannan wasY _x/s =0.51 (g/g). Enzyme formation started with a delay of 30–40 min and stopped with termination of growth. Due to the increased production of mannose by the action of the enzyme the specific growth rate increased from 0.05 to 0.10 h^–1, thus enabling computations of maintenance and yield coefficients for oxygen and carbon dioxide metabolism.

     

Production, purification, and characterization of a low-molecular-mass xylanase from Aspergillus sp. and its application in baking

An extracellular xylanase produced by a Mexican Aspergillus strain was purified and characterized. Aspergillus sp. FP-470 was able to grow and produce extracellular xylanases on birchwood xylan, oat spelt xylan, wheat straw, and corncob, with higher production observed on corncob. The strain also produced enzymes with cellulase, amylase, and pectinase activities on this substrate. A 22-kDa endoxylanase was purified 30-fold. Optimum temperature and pH were 60°C and 5.5, respectively, and isoelectric point was 9.0. The enzyme has good stability from pH 5.0 to 10.0 retaining >80% of its original activity within this range. Half-lives of 150 min at 50°C and 6.5 min at 60°C were found. K _m and activation energy values were 3.8 mg/mL and 26 kJ/mol, respectively, using birch wood xylan as substrate. The enzyme showed a higher affinity for 4-O-methyl-d-glucuronoxylan with a K _m of 1.9 mg/mL. The enzyme displayed no activity toward other polysaccharides, including cellulose. Baking trials were conducted using the crude filtrate and purified enzyme. Addition of both preparations improved bread volume. However, addition of purified endoxylanase caused a 30% increase in volume over the crude extract.     

Formation of ultra-thin films consisting of proteins or polysaccharides and syndiotactic-rich poly-vinyl alcohol mixtures adsorbed at air-solution interface

Ultra-thin films of syndiotactic-rich poly-vinyl alcohol (s-PVA) with several proteins and polysaccharides were prepared by the bubble and frame methods using a mixed dilute aqueous solution (1.5g/dL).The mixed amount of-cyclodextrin (-CD) was the largest among these proteins and polysaccharides giving a weight ratio (-CD/s-PVA) of 1. The ratios of silk fibroin(SF), lysozyme, pepsin, and pectin tos- PVA were 0.58, 0.40, 0.35, and 0.35, respectively. For the-CD/s-PVA and SF/s-PVA blend thin films, the phase separation was observed.     

Carbohydrate compositions of preparations of fungal origin

The fractional composition of the polysaccharides formed by some local strains of basidial fungi (Panus tigrinus, Pleurotus ostreatus, Fomes formentarius, andPhanarechaeta chrysosporium) in a submerged medium on various plant wastes (spent cottonseed pulp and cottonplant stems) has been investigated. Water-soluble polysaccharides, pectin substances, and hemicelluloses have been isolated from the products synthesized by the fungi, and their qualitative and quantitative monosaccharide compositions have been determined.Materials presented at the Second International Symposium of the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October 22–24, 1996).Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 352–357, May–June, 1977.     

Unconventional Cellulose Esters: Synthesis, Characterization and Structure–Property Relations

This paper summarizes selected results obtained during a two-year research project in the framework of the focus program Cellulose and cellulose derivatives (SPP 1011), sponsored by the German Science Foundation (DFG). New synthesis paths for the preparation of the most important cellulose ester, cellulose acetate, were investigated. In contrast to conventional methods, cellulose was converted in a homogeneous phase reaction with acetyl chloride in the presence of different bases, including polyvinyl pyridine and cross-linked polyvinyl pyridine. Moreover, results of the conversion in the new solvent dimethyl sulfoxide/tetrabutylammonium fluoride trihydrate are discussed. The structures obtained were analyzed both on the level of the anhydroglucose unit (AGU) and along the polymer chain. It was found that the addition of a base can significantly change the selectivity of the reaction and thereby the properties of the products (e.g., solubility). No signs of a non-statistical distribution of the acetyl groups along the polymer chains were observed. Furthermore, reactivity and selectivity of the acylation reactions, using in situ activation with p-toluenesulfonyl chloride (Tos-Cl), were studied for different long-chain carboxylic acids (capric-, caprylic-, decanoic-, lauric-, palmitic-, stearic acid). The thermogravimetric analysis of these derivatives showed that the decomposition temperature increased with an increasing number of carbon atoms, starting from 292 °C (cellulose caprate) to 318 °C (cellulose stearate). New cellulose derivatives were synthesized, for example, cellulose adamantoyl ester. For this purpose cellulose was converted homogeneously in N,N-dimethylacetamide/LiCl with free acids in the presence of activating reagents, for example, Tos-Cl or 1,1-carbonyldiimidazol.     

Synthesis and characterization of carboxymethylcelluloses (CMC) from non-wood fibers I.Accessibility of cellulose fibers and CMC synthesis

This paper explores the production of carboxymethylcellulose (CMC) fromseveral bleached cellulose pulps obtained from non-wood species. The chemicalcomposition (-cellulose, hemicellulose and lignin content), the degreeofswelling, viscosity, solubility in concentrated NaOH and crystallinity ofsoda/AQ cellulose pulps from abaca, jute, sisal, linen and Miscanthussinensis were determined. The pulps were carboxymethylated by one andtwo successive reaction steps in aqueous medium under identical conditions. Thedegree of substitution (DS) of CMC was found to be dependent upon the source ofthe cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second. The molar mass of CMC was found to bedependent on the initial intrinsic viscosity of the cellulose pulp. The weightaverage molar mass of our CMCs ranged from 1.5×10⁵ to2.8×10⁵. Increasing the DS up to 2 improved the CMC solubility, butviscosity slightly decreased due to a slight degradation of the polymer.     

Challenge of synthetic cellulose

This article focuses on why and how the chemical synthesis of cellulose was accomplished. The synthesis of cellulose was an important, challenging problem for half a century in polymer chemistry. For the synthesis, a new method of enzymatic polymerization was developed. A monomer of β‐D ‐cellobiosyl fluoride (β‐CF) was designed and subjected to cellulase catalysis, which led to synthetic cellulose for the first time. Cellulase is a hydrolysis enzyme of cellulose; cellulase, inherently catalyzing the bond cleavage of cellulose in vivo, catalyzes the bond formation via the polycondensation of β‐CF in vitro. It is thought that the polymerization and hydrolysis involve a common intermediate (transition state). This view led us to a new concept, a transition‐state analogue substrate, for the design of the monomer. The preparation of cellulase proteins with biotechnology revealed the enzymatic catalytic functions in the hydrolysis and polymerization to cellulose. High‐order molecular structures were in situ formed and observed as fibrils (cellulose I) and spherulites (cellulose II). In situ small‐angle neutron scattering measurements suggested a fractal surface formation of a synthetic cellulose assembly. The principle of cellulose synthesis was extended to the synthesis of other natural polysaccharides, such as xylan and amylose, and unnatural polysaccharides. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 693–710, 2005     

Xylanase Production by Bacillus circulans D1 Using Maltose as Carbon Source

Bacillus circulans D1 is a good producer of extracellular thermostable xylanase. Xylanase production in different carbon sources was evaluated and the enzyme synthesis was induced by various carbon sources. It was found that d-maltose is the best inducer of the enzyme synthesis (7.05 U/mg dry biomass at 48 h), while d-glucose and d-arabinose lead to the production of basal levels of xylanase. The crude enzyme solution is free of cellulases, even when the microorganism was cultivated in a medium with d-cellobiose. When oat spelt xylan was supplemented with d-glucose, the repressive effect of this sugar on xylanase production was observed at 24 h, only when used at 5.0 g/L, leading to a reduction of 60% on the enzyme production. On the other hand, when the xylan medium was supplemented with d-xylose (3.0 or 5.0 g/L), this effect was more evident (80 and 90% of reduction on the enzyme production, respectively). Unlike that observed in the xylan medium, glucose repressed xylanase production in the maltose medium, leading to a reduction of 55% on the enzyme production at 24 h of cultivation. Xylose, at 1.0 g/L, induced xylanase production on the maltose medium. On this medium, the repressive effect of xylose, at 3.0 or 5.0 g/L, was less expressive when compared to its effect on the xylan medium.     

Effect of polysaccharides on the stability and renaturation of soybean trypsin (Kunitz) inhibitor

Thermal denaturation and renaturation of soybean trypsin (Kunitz) inhibitor (STI) were studied by high-sensitivity differential scanning calorimetry in the presence of polysaccharides (dextran, ι- and κ-carrageenans, gum arabic, pectins and dextran sulfate). This study was carried out under conditions of both thermodynamic incompatibility and complex formation of STI and polysaccharides. The presence of polysaccharides did neither influence the denaturation temperature nor the denaturation enthalpy of STI under conditions of their incompatibility with the protein. No polysaccharide (except gum arabic) affected the ability of STI to renature and recover its inhibitory activity after thermal denaturation. At acidic pH values, the protein was shown to form electrostatic complexes with pectins and dextran sulfate. Substantial destabilisation of STI bound to dextran sulfate was observed. In the case of STI/pectin complexes, either a decrease or increase in the stability of STI was observed depending on the complex composition and esterification degree of pectin. The mechanism behind the changes in stability of STI bound to the polysaccharide matrix is discussed. Thermal denaturation of STI in complexes with dextran sulfate and pectin was completely irreversible. This observation indicates a possibility of suppressing antinutritional activities of trypsin inhibitors in soy products.

Schematic presentation of the denaturation of a protein (P) bound to a polymer matrix (M): (A) loose protein occupancy, (B) dense protein occupancy.