Xanthan is a microbial polysaccharide produced from Xanthomonas compestris.
XANTHAN GUM
Synonyms
Xynthan gum.
Biological Source
Xanthan is a microbial polysaccharide produced from Xanthomonas compestris.
Production
One of the latest techniques of
biotechnology, that is, recombinant DNA technology has been duly exploited for
the commercial production of xanthan gum.
First of all the genomic banks of Xanthomonas compestris are meticulously
made in Escherichia coli by
strategically mobilizing the broad-host-range cosmids being used as the
vectors. Subsequently, the conjugal transfer of the genes take place from E. coli into the nonmucoid Xan-thomonas compestris. Consequently,
the wild type genes are duly
separated by virtue of their unique ability to restore mucoid phenotype. As a
result, a few of the cloned plasmids incorporated in the wild type strains of Xanthomonas compestris shall afford an
increased produc-tion of xanthan gum.
Interestingly, the commercial
xanthan gums are avail-able with different genetically controlled composition,
molecular weights and as their respective sodium, potassium or calcium salts.
Morphology
Chemical Constituents
Xanthan gum is composed of chiefly D-glucosyl,
D-mannosyl and D-glucosyluronic acid residues along with variant quantum of
O-acetyl and pyruvic acid acetal. The primary structure essentially comprises
of a cellulose backbone with trisaccharide side chains and the repeating moiety
being a pentasaccharide.
Uses
Xanthan is found to have very wide range of applications. It
is widely used as a stabilizer and suspending agent in emulsion, paints,
agricultural and herbicidal sprays. Applications are found in food,
pharmaceutical and other industries. Specific applications depend upon the
rheological behaviour of xanthan in solution. Synergistic effects are observed
in food when xanthan is mixed with galactomannans such as guar gum or locust
bean gum. It is used as a viscosity controller in abrasives and adhesives. It
finds it valuable applications as gelling agent in explosives and flocculating
agent in extraction.
Marketed Products
Xanthan is the only microbial gum that is currently
produced on commercial scale by Kelco Inc., San Diego, United States, and by
Rhone Poulene, S.A., Melle, France. It is marketed under the variety of trade
names like Keltrol©, Kelzan© or Rhodogel©.
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