Polysaccharides xanthan gum

We have already mentioned that xanthan gum solutions are tolerant to both acids and bases. Solutions of xanthan gum also have excellent compatibility with many surfactants, water-miscible solvents, and other thickeners. As an anionic polysaccharide, xanthan gum is most stable with anionic surfactants (up to 20% active), nonionic surfactants (up to 40% active), and amphoteric surfactants (up to... 

The bacterial polysaccharide Xanthan Gum comprises a regularly substituted cellulose backbone, and shows quite different solution properties from the plant anyloids. No ability to interact with agarose or -carrageenan was observed for Xanthan Gum. 

NMR spectra of chiral molecules aligned in a chiral liquid crystalline solvent. A method for the visualization of enantiomers using natural abundant filtered single and double quantum selective refocusing experiments has been proposed and its application to small chiral molecules demonstrated. A lyotropic liquid crystalline phase of an aqueous solution of polysaccharide xanthan gum has been reported as a scalable weak alignment medium for enantiodiscrimination of water soluble chiral molecules. ... 

T. Basavaraju Demappa, S.K. Rai, Miscibility studies of polysaccharide xanthan gum and PEO (polyethylene oxide) in dilute solution, Carbohyd Polytn, 69 462-466,2007. 

Xanthan Gum. As a result of a project to transform agriculturally derived products into industrially usefiil products by microbial action, the Northern Regional Research Laboratories of the USDA showed that the bacterium TCanthomonas campestris - noduces a polysaccharide with industrially usefiil properties (77). Extensive research was carried out on this interesting polysaccharide in several industrial laboratories during the eady 1960s, culminating in commercial production in 1964. 

Xanthan gum [11138-66-2] is an anionic heteropolysaccharide produced by several species of bacteria in the genus Aanthomonas A. campestris NRRL B-1459 produces the biopolymer with the most desirable physical properties and is used for commercial production of xanthan gum (see Gums). This strain was identified in the 1950s as part of a program to develop microbial polysaccharides derived from fermentations utilizing com sugar (333,334). The primary... 

The alternative large scale recovery method to precipitation is ultrafiltration. For concentration of viscous exopolysaccharides, ultrafiltration is only effective for pseudoplastic polymers (shearing reduces effective viscosity see section 7.7). Thus, pseudoplastic xanthan gum can be concentrated to a viscosity of around 30,000 centipoise by ultrafiltration, whereas other polysaccharides which are less pseudoplastic, are concentrated only to a fraction of this viscosity and have proportionally lower flux rates. Xanthan gum is routinely concentrated 5 to 10-fold by ultrafiltration. 

Xanthan gum is a long-chain polysaccharide composed of the sugars glucose, mannose, and glucuronic acid. The backbone is similar to cellulose, with added side chains of trisaccharides (three sugars in a chain). 

A polysaccharide such as xanthan gum is a chain of sugars. Some familiar polysaccharides are starch and cellulose. The backbone of xanthan gum is similar to cellulose, but the trisaccharide side chains of mannose and glucuronic acid make the molecule rigid, and allow it to form a right-handed helix. These features make it interact with... 

Carboxymethylcellulose, polyethylene glycol Combination of a cellulose ether with clay Amide-modified carboxyl-containing polysaccharide Sodium aluminate and magnesium oxide Thermally stable hydroxyethylcellulose 30% ammonium or sodium thiosulfate and 20% hydroxyethylcellulose (HEC) Acrylic acid copolymer and oxyalkylene with hydrophobic group Copolymers acrylamide-acrylate and vinyl sulfonate-vinylamide Cationic polygalactomannans and anionic xanthan gum Copolymer from vinyl urethanes and acrylic acid or alkyl acrylates 2-Nitroalkyl ether-modified starch Polymer of glucuronic acid... 

Scleroglucan is a polysaccharide secreted by the mycelia of certain microorganisms. It is produced by aerobic fermentation of D-glucose by such microorganisms. Scleroglucan has been proposed as a better alternative to xanthan gum for drilling fluid compositions [666]. 

Xanthan Gum. Xanthan gum is produced by the bacterium Xanthomonas campestris. Commercial productions started in 1964. Xanthans are water-soluble polysaccharide polymers with the following repeating units [502], as given in Table 17-5 and Figure 17-6. 

Most of the xanthan gum used in oil field applications is in the form of a fermentation broth containing 8% to 15% polymer. The viscosity is less dependent on the temperature in comparison with other polysaccharides. 

Stabilizing agents are used to maintain drilling fluid rheological properties at highly elevated downhole temperatures. Chromium and chromium-free lignosulfonates, polyglycol ethers, sodium polystyrene sulfonate-co-maleic anhydride), and a melanin polymer have been used in this application. Additives such as sodium diethyldi-thiocarbamate have been used to stabilize aqueous polysaccharides such as xanthan gum (18). 

Other natural polysaccharides used as thickening agents include gum arabic, gum tragacanth and xanthan gum, but these are of diminishing significance nowadays. 

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