Cellulose bacterial

Bacterial cellulose (BC) is biodegradable polyester produced by specific genera of bacteria Acetobacter, Rhizobium, Agrobacterium) and certain algae [33,34]. The chemical structure of BC is similar to that of plant cellulose, but BC possesses considerably superior physical, mechanical, and biological properties when compared to plant cellulose [35]. BC is chemically pure and does not contain any impurities such as lignin and hemicelluloses that are associated with plant cellulose. It exhibits a fibrous network 

It has ribbon shape with diameter ranging from 8 to 50 nm, which is about a 1000 times smaller than that of common plant fibers (10-600 pm) [304]. The fibril is composed of a bundle of much finer microfibrils 2-4 nm in diameter [305, 306]. 

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Bacterial cellulose Bacterial leaching Bacterial removal Bacteria, luminous Bactericide... 

A commercial bacterial cellulose product (CeUulon) was recently introduced by Weyerhaeuser (12). The fiber is produced by an aerobic fermentation of glucose from com symp in an agitated fermentor (13,14). Because of a small particle diameter (10 P-m), it has a surface area 300 times greater than normal wood cellulose, and gives a smooth mouthfeel to formulations in which it is included. CeUulon has an unusual level of water binding and works with other viscosity builders to improve their effectiveness. It is anticipated that it wiU achieve GRAS status, and is neutral in sensory quaUty microcrystaUine ceUulose has similar attributes. 

Bacterial Cellulose. Development of a new strain of Acetobacter may lead to economical production of another novel ceUulose. CeUulon fiber has a very fine fiber diameter and therefore a much larger surface area, which makes it physicaUy distinct from wood ceUulose. Its physical properties mote closely resemble those of the microcrystalline ceUuloses thus it feels smooth ia the mouth, has a high water-binding capacity, and provides viscous aqueous dispersions at low concentration. It iateracts synergisticaUy with xanthan and CMC for enhanced viscosity and stabUity. 

The membrane is critically important in osomometry. Selection of a membrane involves reconciliation of high permeability toward the solvent with virtual impermeability to the smallest polymer molecules present in the sample. Membranes of cellulose are most widely used. Commercially Regenerated cellulose film is a common source. The undried gel cellophane film is often preferred, but the dry film may be swollen in water (or in aqueous solutions of caustic or zinc chloride ) to satisfactory porosity. Useful cellulose membranes may also be prepared by denitration of nitrocellulose films/ and special advantages have been claimed for bacterial cellulose films. The water in the swollen membrane in any case may be replaced by a succession of miscible organic solvents ending with the one in which osmotic measurements are to be made. Membranes of varying porosity may be... 

Reticulated bacterial cellulose may be used in place of a conventional gellant or in combination with conventional gellants to provide enhanced drilling muds [1837]. The addition of relatively small quantities of reticulated bacterial cellulose to wellbore drilling muds enhances their rheologic properties. 

Reticulated Bacterial Cellulose. A cellulose with an intertwined reticulated structure, produced from bacteria, has unique properties and functionalities unlike other conventional celluloses. When added to aqueous systems, reticulated bacterial cellulose improves the fluid rheology and the particle suspension over a wide range of conditions [1836]. Test results showed advantages in fluid performance and significant economic benefits by the addition of reticulated bacterial cellulose. 

Relatively small quantities of a bacterial cellulose (0.60 to 1.8 g/liter) in hydraulic fracturing fluids enhance their rheologic properties [1425]. Proppant suspension is enhanced and friction loss through well casings is reduced. 

Bacterial cellulose, dextran and many other bacterial polysaccharides are composed entirely of D-glucose units the levans are condensation polymers of D-fructose. Dextrans from different species of Leuconostoc... 

Tarr and Hibbert13 published the first detailed study of the formation of bacterial cellulose. A systematic series of experiments, conducted with a view to obtaining a culture medium which did not support visible growth of A. xylinum until a suitable source of carbon was added, indicated that a solution (pH 5.0) containing 0.1% asparagine, 0.5% potassium dihydrogen phosphate, 0.1% sodium chloride and 0.5% ethanol satisfied these requirements. Maximum polysaccharide formation oc-... 

Schmidt and coworkers17 showed by conductometric titrations that bacterial cellulose resembled all undegraded celluloses in its content of 0.28% of carboxyl groups. 

Since bacterial cellulose from all suitable carbohydrate substrates i8 identical with natural cellulose, its industrial importance20 is obvious. Relatively large amounts of bacterial cellulose were produced in Germany during the first World War. More recently products similar to parchment, mercerized cotton, cellulose nitrate,21 acetate14 and viscose rayons have been produced from bacterial cellulose. 

From a theoretical standpoint, further study of the formation of bacterial cellulose might yield some information regarding the mechanism of plant synthesis. 

Bacterial ADPGPP enzymes, 12 491 Bacterial a-amylases, 10 280 Bacterial artificial chromosome (BAC) vectors, 12 508 Bacterial cellulose, 20 557 Bacterial genera, nitrogen fixation by, 17 295-296... 

The substances generally used as osmotic membranes include collodion (nitrocellulose of 11-13.5 per cent nitrogen) regenerated cellulose, obtained by denitration of collodion gel cellophane that has never permitted to dry after manufacture bacterial cellulose, obtained by the action of certain strains of bacteria rubber, poly (vinyl alcohol) polyurethances poly (vinyl butyral) and polychlorotrifluoroethylene. At present gel cellophane is most widely used. 

Schlufter, K., Schmauder, H.P., Dorn, S., and Heinze, T., Bacterial cellulose in the ionic liquid l-n-butyl-3-methylimidazolium chloride, Macromol. Rapid Commun., 27, 1670-1676,2006. 

Lamellar, single crystals of ivory-nut mannan were studied by electron diffraction. The base-plane dimensions of the unit cell are a = 0.722 nm and b = 0.892 nm. The systematic absences confirmed the space group P212121. The diffraction pattern did not change with the crystallization temperature. Oriented crystallization ofD-mannan with its chain axis parallel to the microfibril substrates, Valonia ventricosa and bacterial cellulose, was discovered ( hetero-shish-kebabs ). 

The bacterial cellulose synthase from Acetobacter xylinum can be solubilized with detergents, and the resulting enzyme generates characteristic 1.7 ran cellulose fibrils (Fig. 20-4) from UDP-glucose.125/127-129 These are similar, but not identical, to the fibrils of cellulose I produced by intact bacteria.125 130 Each native fibril appears as a left-handed helix which may contain about nine parallel chains in a crystalline array. Three of these helices appear to coil together (Fig. 20-4) to form a larger 3.7-nm left-handed helical fibril. Similar fibrils are formed by plants. In both... 

Other examples of exocellular homopolysaccharides whose biosynthetic process has been investigated include D-mannuronan,204,205 an intermediate in the biosynthesis of bacterial alginic acid (mentioned in Section III,l,c), and bacterial cellulose. 

Colvin155 was the first to postulate a lipid-bound D-glucose as an intermediate in the biosynthesis of bacterial cellulose. Lipid-sugar derivatives, tentatively identified as lipid-diphosphate-D-glucose, lipid-diphosphate-cellobiose, and, perhaps, higher polymers, were detected in this system.128 These lipid-sugar compounds, which were acid- and alkali-labile, seemed to be formed prior to cellulose, and their formation was inhibited by adding... 

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