Acetobacter xylinum, cellulose produced

Tobacco primary cell wall and normal bacterial Acetobacter xylinum cellulose formation produced a 36.8 3A triple-stranded left-hand helical microfibril in freeze-dried Pt-C replicas and in negatively stained preparations for transmission electron microscopy (TEM). A. xylinum growth in the presence of 0.25 mM Tinopal disrupted cellulose microfibril formation and produced a... 

The kind of polysaccharides that are isolated from different bacteria are as follows Alginate, a linear copolymer with (l-4)-linked p-D-mannuronate and its a-L-guluronate residues that is produced by two bacterial genera Pseudomonas species and Azotobacter vinelandii [4]. Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications. Cellulose, a p (1—>4) linked D-glucose unit obtained from Acetobacter xylinum. Cellulose of plant origin is usually impure as it contains... 

Iwata, T., Indrarti, L., Azuma, J., 1998. Affinity of hetnicellulose for cellulose produced by Acetobacter xylinum. Cellulose 5, 215—228. 

Isolation and sequencing of the cellulose synthase gene(s) has not been accomplished yet however, DNA from Acetobacter xylinum containing this gene(s) was cloned into broad host-range plasmid vectors (82). These vectors were mobilized into Pel- mutants to test for complementation. To date, this approach has not produced a pellicle-forming transconjugant from a Pel- mutant of Acetobacter (82). The direct correlation between cellulose production and presence of plasmid DNA in Acetobacter has been reported... 

The gram negative bacterium Acetobacter xylinum produces a ribbon of crystalline cellulose I whose neutral sugar content is 96.8% glucose and 3.2% xylose (1). Growth of A. xylinum in a medium containing... 

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... 

It is thus very likely that at least cellulose produced by Acetobacter xylinum is synthesized by simultaneous polymerization and crystallization. Especially interesting remaining problems in this system are the questions of nucleation of new fibrils, the reasons for the limiting diameter of the fibrils, and the defect structure of the only partially crystalline cellulose which is not uniform across the fibril. 

Disaccharide fluorides have been treated with cellulase to produce cellulose, amylose, and xylan.316 A mutant strain of Acetobacter xylinum produced cellulose that imparted higher tensile strength and superior properties to paper than did cellulose from higher plants.317 An economical mass production technique has been devised for it. 

It has been known for some time that the more crystalline native celluloses from algae and from Acetobacter xylinum produce diffraction patterns that have many features in common with those of the crystalline celluloses from the higher plants, such as ramie, but that cannot be indexed as simply or on the basis of the same unit cell. The new information from the CP-MAS UMR spectra, together with that from the Raman spectra, suggests some bases for understanding these differences, and directions for further explora-t ions. 

Recently, bacterial cellulose, produced by Acetobacter Xylinum, was used as reinforcement in composite materials with a starch thermoplastic matrix [230]. The composites prepared with bacterial cellulose displayed better mechanical properties than those with vegetable cellulose fibers. 

Acetobacter xylinum produces two forms of cellulose (1) cellulose I, the rib-bon-like polymer, and (2) cellulose II, the thermodynamically more stable amorphous polymer [9]. They can be divided according to their morphological localization as intracellular polysaccharides located inside, or as part of the cytoplasmic membrane cell wall polysaccharides forming a structural part of the cell wall and extracellular polysaccharides located outside the cell wall. Extracellular polysaccharides occur in two forms loose slime, which is non-adherent to the cell and imparts a sticky consistency to bacterial growth on a solid medium or an increased viscosity in a liquid medium and microcapsules or capsules, which adhere to the ceU wall. 

Fig. 10.7 Examples of biomedical applications of BC are meniscus replacements (pig meniscus on the left, BC meniscus on the right), artificial blood vessels and wound dressing for skin heaiing [76-78], Nanocellulose (bacterial cellulose, BC), such as that produced by Acetobacter xylinum, has shown promising results as a replacement material for small diameter vascular grafts (Fig. 10.8). These BC tubes have been tested in a pig model as an infrarcnal aortic bypass and show promising results for use as vascular grafts in the future...

Hirai A., Tsuji M., Horii F., TEM study of band-like cellulose assemblies produced by Acetobacter xylinum at 4°C, Cellulose, 9, 2002, 105. 

Williams, W.S. and Cannon, R.E. 1989. Alternative environmental roles for cellulose produced by Acetobacter xylinum. Applied and Environmental Microbiology 55(10) 2448-2452. 

Kai, A., Mondal, I., 1997. Influence of substituent of direct dye having bisphenylenebis (azo) skeletal structure on structure of nascent cellulose produced by Acetobacter xylinum [I] different influence of direct red 28, blue 1 and 15 on nascent structure. International Journal of Biological Macrotnolecules 20, 221—231. 

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