Bacterial cellulose structure

Figure 4.4. SEM (a) and TEM (b) of bacterial cellulose structure. Reproduced from [36] with permission from Springer.

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. 

The biosynthesis of most crystalline polymers is not well understood. The mechanism by which structural and insoluble proteins are assembled from monomers into structures such as cell membranes is almost completely unknown (33). A notable exception is the biosynthesis of polysaccharides which is believed to take place by phosphate displacement reactions of an activated subunit with the help of an enzyme system (33). The polymerization of bacterial cellulose is perhaps studied in most detail. Here the research has been helped because the reaction of monomer to crystalline polymer occurs extracellularly, remote from the bacterial surface (34). 

Mukeethaler, K. The structure of bacterial cellulose. Biochim. Biophjrs. 

Fig. 13. C-CPMAS spectrum of bacterial cellulose containing mainly the la and a minor amount of the Ip polymorphs. Below the calculated chemical shift values according to the chemical shift crystal structure refinement are shown.

Bacterial cellulose membranes were modified with acid groups to produce a proton conductive membrane without compromising the structure of the cellulose membrane. 

There is a wealth of data, both in the scientific and patent literature, on the chemical modification of plant cellulose. All of these methods are equally applicable to bacterial cellulose given that the two types of cellulose are chemically identical. However, it is the physical structure of bacterial cellulose membranes that make them a potential material for PEM fuel cells. Therefore, the aim is to modify bacterial cellulose pellicules in a manner that retains the structure of the cellulose and does not... 

The crystalline component of ramie and cotton differs In chemical shift and line splittings from that of valonia and bacterial cellulose. This suggests that there Is some difference in crystal structure among these samples, although the crystalline form Is generally assumed to be cellulose I for all these materials. 

The existence of an ordered structure in cellulose is shown conclusively by wide-angle x-ray diffraction (WAXD) and electron diffraction studies (3). The diffraction patterns exhibit reasonably well-definid reflections for which unit cells have been defined. There are four basic recognized crystalline modifications, namely, cellulose I, II, III and IV. By the WAXD method as proposed by Hermans (4,5) it has been found that native celluloses of different biological origin vary in crystallinity over wide limits, from A0% in bacterial cellulose to 60 in cotton cellulose and 70 in Valonia cellulose. 

M. Koyama, W. Helbert, T. Imai, J. Sugiyama, and B. Henrissat, Parallel-up structure evidences the molecular directionality during biosynthesis of bacterial cellulose, Proc. Natl. Acad. Sci. U.S.A., 94 (1997) 9091-9095. 

J. R. Colvin, Tip-growth of bacterial cellulose microfibrils and its relation to tire crystallographic fine structure of cellulose, J. Polym. Sci. B, 4 (1966) 747-754. 

Kim et al. studied the effect of bacterial cellulose on the transparency of PLA/bacterial nanocomposites, since bacterial cellulose had shown good potential as reinforcement or preparing optically transparent materials due to its structure, which consists of ribbon-shaped fibrils with diameters in the range from 10 to 50 nm. They found that light transmission of the PLA/bacterial cellulose nanocomposite was quite high due to the size effect of... 

Bacterial polysaccharides are a very heterogeneous group and are clearly of several biosynthetic types. Many are closely equivalent to the polysaccharide (O-antigenic-type) chains of lipopolysaccharide and have presumably been released by hydrolysis, rather than transferred to lipid A or core structures. Some, such as bacterial hyaluronate, somewhat resemble wall polymers (some teichuronic acids, in this case), but have no exact counterparts. Others, such as bacterial cellulose and colominic acid (polysialic acid) are very different from... 

Cellulose, like the polysaccharides above, has certain drawbacks. These include poor solubility in common solvents, poor crease resistance, poor dimensional stability, lack of thermoplasticity, high hydrophilicity, and lack of antimicrobial properties. To overcome such drawbacks, the controlled physical and/or chemical modification of the cellulose structure is essential [160]. Introduction of functional groups into cellulose can alleviate these problems while maintaining the desirable intrinsic properties of cellulose. Apart from the conventional plant source, cellulose is also obtained from bacteria, termed bacterial cellulose. 

Nanocellulose, such as that produced by the bacteria Gluconacetobacter xylinus (bacterial cellulose, BC), is an emerging biomaterial with great potential in several applications. The performance of bacterial cellulose stems from its high purity, ultra-fine network structure and high mechanical properties in the dry state [114]. These features allow its applications in scaffold for tissue regeneration, medical applications and nanocomposites. A few researchers have used bacterial cellulose mats to reinforce polymeric matrices and scaffolds with wound healing properties [115-121]. BC is pure cellulose made by bacterial fabrication via biochemical... 

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