Xanthan gum production

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. 

Casas, J.A.,Santos, V.E.,Garcia-Ochoa F., 2000, Xanthan gum production under several operational conditions molecular structure and rheological properties. Enzyme Microb. Technol. 26 282-291... 

Kalogiannis S, lakovidou G, Liakopoulou-Kyriakides M, Kyriakidis DA, Skaracis GN. Optimization of xanthan gum production by Xanthomonas campestris grown in molasses. Process Biochem 2003 39 249-56. 

Garcla-Ochoa F, Santos VE, Casas JA, Gomez E. Xanthan gum production, recovery, and properties. 

Funahashi, H., K. I. Hirai, T. Yoshida, and H. Taguchi (1988b). Mechanistic analysis of xanthan gum production in a stirred tank, J. Ferment. Technol., 3, 355-364. 

Rosalam S. England R. (2006). Review of xanthan gum production from unmodified starches by Xanthomonas cowprestrissp. Enzyme and Microb Tech, 39(2), 197-207. 

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. 

Health nd Safety Factors. The toxicological and safety properties of xanthan gum have been extensively investigated (82). On the basis of these studies, the EDA issued a food additive order in 1969 that allowed the use of xanthan gum in food products without specific quantity limitations. 

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... 

For products intended to remain stable dispersions for an extended period, a particle size of 2 p.m or less is desirable. A thickening agent is usuaUy added after the reaction has been completed and the mixture is cooled in order to prevent settling and agglomeration. Examples of thickeners are guar gum, xanthan gum, and hydroxyethylceUulose. The final products are generaUy between 40 and 50% soUds, with a viscosity of 1500 5000 mPa-s(=cP). 

Microcrystalline ceUuloses ate marketed under the trade name Avicel. The physical characteristics of microcrystalline ceUuloses differ markedly from those of the original ceUulose. The ftee-flowiag powders have particle sizes as smaU as 0.2—10 p.m. Avicel ceUuloses coated with xanthan gum, guar gum, or carboxy-methylceUulose to modify and stabilize their properties are also available. The Avicel products are promoted for use ia low calorie whipped toppiags andiciags andia fat-reduced salad dressiags and frozen desserts (see Fat substitutes). 

From a commercial point of view, xanthan gum is the most important microbial exopolysaccharide currently being manufactured. Therefore, we shall consider the fermentation of this product by Xanthomonas campestris in some detail. 

Figure 7.5 Production of xanthan gum in batch culture using X. campestris. Bacterial dry weight ( ) xanthan gum ( ) residual glucose ( ) residual glutamate (A). Adapted from Microbial exopolysaccharide, Yenton etai pp 217-261. In biomaterials Novel Materials from Biological Sources, D Byrom (Ed), MacMillan Academic Professional Ltd, 1991.

Polar organic solvents readily precipitate exopolysaccharides from solution. The solvents commonly used are acetone, methanol, ethanol and propan-2-ol. Cation concentration of the fermentation liquor influences the amount of solvent required for efficient product recovery. In the case of propan-2-ol, increasing the cation concentration can lead to a four-fold reduction in die volume of solvent required to precipitate xanthan gum. Salts such as calcium nitrate and potassium chloride are added to fermentation broths for this purpose. 

Figure 9.6 shows the schematic diagram for production of xanthan gum with inlet and outlet streams. 

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. 

For suspensions primarily stabilized by a polymeric material, it is important to carefully consider the optimal pH value of the product since certain polymer properties, especially the rheological behavior, can strongly depend on the pH of the system. For example, the viscosity of hydrophilic colloids, such as xanthan gums and colloidal microcrystalline cellulose, is known to be somewhat pH- dependent. Most disperse systems are stable over a pH range of 4-10 but may flocculate under extreme pH conditions. Therefore, each dispersion should be examined for pH stability over an adequate storage period. Any... 

---