Biopolymers xanthan

The oil price rises in the 1970s stimulated interest in Enhanced Oil Recovery (EOR), and fairly rapidly the biopolymer xanthan, the extracellular polysaccharide from the bacterium Xanthomonas campestris. an organism which normally resides on cabbage leaves, was identified as a leading contender as a viscosifier for polymer enhanced water flooding. 

Depletion flocculation has also been induced in oil-in-water emulsions by adding different concentrations of a non-adsorbing biopolymer (xanthan) to the aqueous phase. At low frequencies, the attenuation coefficient of the emulsions decreased with increasing... 

BIOPOLYMERS Xanthan Scleroglucan - high productivity in brine - resistant at high shear rates and temperature - adsorption (salt) - problematic injec-tability - sensitive to microbial degradation - sensitive to oxygen... 

This chapter is divided into four parts. In the first part, a description of experimental studies related to water-soluble polymers is given. In the second part, factors affecting the flow behavior of partially hydrolyzed polyacrylamide will be examined. In the third part, the flow behavior of biopolymers (xanthan) will be reviewed. In the last part, rheological properties of hydrophobically associating polymers will be discussed. 

He did see considerable promise for polymers of HEC type and the biopolymers xanthan and scleroglucan were also found to be quite acceptable. However, Akstinat did not present very detailed stability results for the polymers in his study. Also, note that in the work of Akstinat, and in the work of Davison and Mentzer (1980), the objective was to find stable polymers for high-salinity brines (in the latter case based on sea water from the North Sea). It is well known, and it is discussed in detail below, that polyacrylamides are severely restricted in their performance in hard brines (i.e. brines containing divalent ions Ca ", Mg " ) (Zaitoun and Poitie, 1983 Moradi-Araghi and Doe, 1984). 

Tertiary recovery focuses on the exploitation of wells after primary (natural pressure of the well) and secondary recovery ( use of water and gas under pressure) have been accomplished. - Water-soluble pol nners are used in polymer flooding. The biopolymer - xanthan gum has proven to have high shear-stability and is insensitive to high electrolyte concentrations at high or low pH. 

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... 

Glucose A 6-carbon sugar molecule, which is the building block of natural substances like cellulose, starch, dextrans, xanthan, and some other biopolymers and used as a basic energy source by the cells of most organisms. 

R. M. Hodge. Particle transport fluids thickened with acetylate free xanthan heteropolysaccharide biopolymer plus guar gum. Patent US 5591699,1997. 

H. Liu and Y. Zhang. Rheological property of the xanthan biopolymer flooding systems. J Univ Petrol, China, 19(4) 41-44, August 1995. 

The order-disorder transition temperature is a crucial parameter for biopolymers like Shellflo-S and xanthan, as it controls both rheology and breaking sensitivity. 

Norton, C.J., Falk, D.O., and Luetze l Schwab, U.E. "Xanthan Biopolymer Semi-Pi lot Fermentation," SPE paper 8420, 1979 SPE Annual Technical Conference and Exhibition, Las Vegas, Septemeber 23 26. 

Kaplan, D.L. (1998) Biopolymers from Renewable Resources, (ed D.L. Kaplan), Springer, Berlin, Chapter 1. Sandford, P.A. and Baird, J. (1983) The Polysaccharides (ed G.O. Aspinall), Academic Press, New York, Chapter 7. Garcia-Ochoa, F., Santosa, V.E., Casas, J.A. and Gomez, F. (2000) Xanthan gum production, recovery, and properties. Biotechnology Advances, 18, 549-579. 

Figure 9 shows a dimensionless standardized material function of two pseudoplastic fluids often used in biotechnology. It proves that the examined polymers (CMC—a chemical polymer and Xanthane—a biopolymer) are not completely similar to each other if they were, the exponent m must not have been different by a factor of 2 (insert in Fig. 9). 

Almost every biological solution of low viscosity [but also viscous biopolymers like xanthane and dilute solutions of long-chain polymers, e.g., carbox-ymethyl-cellulose (CMC), polyacrylamide (PAA), polyacrylnitrile (PAN), etc.] displays not only viscous but also viscoelastic flow behavior. These liquids are capable of storing a part of the deformation energy elastically and reversibly. They evade mechanical stress by contracting like rubber bands. This behavior causes a secondary flow that often runs contrary to the flow produced by mass forces (e.g., the liquid climbs the shaft of a stirrer, the so-called Weissenberg effect ). 

In addition to the necessary protection of the contents of the emulsion droplets, effective encapsulation technology requires that the release of the active matter be controlled at a specified rate. Benichou et aL (2004) have demonstrated that a mixture of whey protein isolate (WPI) and xanthan gum can be successfully used for the controlled release of vitamin Bi entrapped within the inner aqueous phase of a multiple emulsion. The release profile, as a function of the pH of the external aqueous phase, is plotted in Figure 7.25. We can observe that the external interface appears more effectively sealed against release of the entrapped vitamin at pH = 2 than at pH = 4 or 7. It was reported that an increase in the protein-to-potysaccharide ratio reduced the release rate at pH = 3.5 (Benichou et aL, 2004). More broadly, the authors suggest that compatible blends of biopolymers (hydrocolloids and proteins) should be considered excellent amphiphilic candidates to serve as release controllers and stability7 enhancers in future formulations of double emulsions. So perhaps mixed compatible biopolymers wall at last allow researchers to... 

Almost every biological solution of low viscosity [but also viscous biopolymers like xanthane and dilute solutions of long-chain polymers, e.g., carboxymethyl-cellulose (CMC), polyacrylamide (PAA), and polyacrylnitrile (PAN)] displays... 

As with higher organisms, a common feature of bacteria is the production of extracellular polysaccharides, during growth. Within the last 20 years, the large-scale production of microbial biopolymers has become feasible, and mainly two microbial products, i.e., xanthan and dextran are widely used in the pharmaceutical industry today. 

Vitamin Bi was entrapped in an inner aqueous phase of a double emulsion stabilized by a mixture of whey protein isolate and xanthan as the external gum. The release of the vitamin was modulated by altering the pH or the ratio of the two biopolymers. The increased rate of release of the vitamin as pH was increased from 2 to 7 has been attributed to the decreased electrostatic interaction between whey protein isolate and xanthan. Increasing the rigidity of the external interface by increasing the amount of xanthan also decreased the rate of release of the vitamin (Benichou et al. 2004). 

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