Health & Environmental Research Online (HERO)


Print Feedback Export to File
1630671 
Journal Article 
Aspects of the process for xanthan production 
Galindo, E 
1994 
Yes 
Food and bioproducts processing
ISSN: 0960-3085
EISSN: 1744-3571 
72 
C4 (1994) 
227-237 
Xanthan gum is a high molecular weight polysaccharide produced by bacteria of the genus Xanthomonas. Its production process involves microbiological and bioprocess engineering issues. This paper reviews the work done by the author's group and collaborators in three aspects of xanthan production: microbiology, fermentation and downstream processing. A extensive screening program has led to the isolation of a number of Xanthomonas strains having improved characteristics. Xanthan production ability has been correlated with bacterial virulence in cabbage plants. Preservation of this bacteria has been studied in successive agar slopes and a novel technique has been developed which uses cabbage seeds as means of culture preservation. Xanthomonas turned out to be a quite stable bacteria in terms of xanthan production. Xanthan fermentation broths have been rheologically characterized. A novel and simple technique for measuring the apparent yield stress has been developed, as this parameter plays a crucial role in the fermenter's mixing characteristics. Viscoelasticity (normal stresses) has been studied in fermentation broths and reconstituted xanthan solutions under a variety of conditions. Power drawn and well-mixed caverns have been characterized for a variety of impellers (Rushton, 45 degree pitched blades turbine, Lightnin A-315, Scaba 6SRGT and Intermig) in xanthan broths, commercial gum solutions and transparent Carbopol solutions. In-fermenter power measurement by a strain-gauges telemetry system allowed the comparison of impeller performance during actual fermentations. Large, dual impellers were shown to maximize xanthan production under the minimum energy expediture. Heat treatment of the broth (needed for its pasteurization) changed drastically the rheological properties of the broth. Xanthan recovery by precipitation with isopropanol was studied in a mixing tank with various impellers. The broth's xanthan concentration and impeller type affected importantly the polymer yields. 
Xanthomonas