This document focuses on polysaccharides, specifically xanthan gum, detailing their structures, classifications, and properties. It describes storage, structural, and acidic polysaccharides, alongside the role of bacterial capsular polysaccharides. Additionally, it covers the production, fermentation conditions, and unique rheological properties of xanthan gum.

1. Polysaccharides – Xanthan Gum
M.Sc. Biotechnology Part II (Sem III)
Paper III - Unit III
Mumbai University
By: Mayur D. Chauhan
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2. Polysaccharides
• They are long chains of polymeric
carbohydrates.
• Monosaccharides are linked together by
Glycosidic bonds.
• Homogenous Polysaccharide & Heterogenous
Polysaccharide.
• Properties depend upon the monosaccharide
units.
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3. Types of Polysaccharides
Storage
Acidic
Structural
Bacterial
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4. 1. Storage Polysaccharides
• Starch: Starch is glucose polymer in plants in
which glucopyranose units are bonded by alpha-
linkages. It is made up of a mixture of amylose
(15–20%) and amylopectin (80–85%)
• Glycogen: Glycogen is the analogue of starch and
is sometimes referred to as animal starch, having
a similar structure to amylopectin but more
extensively branched and compact than starch.
Glycogen is a polymer of α(1→4) glycosidic bonds
linked, with α(1→6) linked branches
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5. 2. Structural Polysaccharides
• Arabinoxylans: They are found in both the
primary and secondary cell walls of plants and
are the copolymers of two pentose sugars:
arabinose and xylose.
• Cellulose: Cell wall component of plants.
Cellulose is a polymer made with repeated
glucose units bonded together by beta-
linkages.
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6. • Chitin: Chitin is one of many naturally
occurring polymers and it forms a structural
component of many animals, such as
exoskeletons. It is closely related to cellulose
in that it is a long unbranched chain of glucose
derivatives.
• Pectins: Pectins are a family of complex
polysaccharides that contain 1,4-linked α-D-
galactosyluronic acid residues. They are
present in most primary cell walls and in the
non-woody parts of terrestrial plants.
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7. 3. Acidic Polysaccharides
• Polysaccharides that contain carboxyl groups,
phosphate groups or sulfuric ester groups.
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8. 4. Bacterial Capsular Polysaccharides
• Pathogenic bacteria commonly produce a thick, mucous-
like, layer of polysaccharide. This "capsule" cloaks antigenic
proteins on the bacterial surface that would otherwise
provoke an immune response and thereby lead to the
destruction of the bacteria.
• Mixtures of capsular polysaccharides, either conjugated or
native are used as vaccines.
• Bacteria and many other microbes, including fungi and
algae, often secrete polysaccharides to help them adhere
to surfaces and to prevent them from drying out.
• Examples: X. campestris, X. phaseoli, X. malvacearum, X.
carotae, X. juglandis etc.
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9. Xanthan Gum
• Polysaccharide secreted by the bacterium
Xanthomonas campestris.
• Xanthomonas campestris was originally
isolated from the Rutabaga plant.
• It produces viscid and gummy colonies on agar
media.
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10. X. Campestris
grown by using
carbohydrate as
substrate
X. Campestris
grown by using
Cabbage extracts
as substrate.
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11. • Commercially produced Xanthan Gum was
identical to naturally produced Xanthan Gum.
• Essential requirements during the process of
Fermentation:
1. Glucose, Sucrose, Starch, Corn sugar, Acid
whey (Cheese production) as Carbon Sources.
2. Ammonium chloride, Magnesium sulphate
and certain trace elements were required for
optimum growth.
3. pH should be maintained
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12. • During fermentation, the pH of the medium
decreases due to the formation of metabolic
acids.
• Xanthan gum also has acidic functions but if
the pH reaches a critical point like 5.0, the
gum production decreases drastically.
• A nearly neutral pH allows the gum synthesis
to continue until all the carbohydrate
substrate gets utilized and the fermentation is
complete.
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13. • Optimum temperature should be around 280 C
• Also at 1-5% glucose concentration has been
found to provide best xanthan gum yields.
• Aeration and Agitation should be proper
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14. Structure of Xanthan Gum
• It is either a single or multi stranded helix
• It is a high molecular weight natural
polysaccharide.
• Molecular weight is 2-20 x 106 Daltons
• It is a 5 sugar repeating unit – D-glucose, D-
glucuronic acid, D-mannose and 2 types of
carboxyl groups acetate and pyruvate.
• It exists as either a rod like shape or a worm
like shape but with low flexibility.
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16. Protocol
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17. • Polysaccharide are precipitated by using
Isopropyl alcohol or acetone.
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18. Properties of Xanthan Gum
• 1. Rheological Properties: Most important
property of Xanthan gum is to control the
rheological properties of fluids.
• Xanthan gum gets dissolved in hot or cold
water upon stirring to form a high viscosity
even at low gum concentrations.
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20. • At low concentrations of Xanthan Gum (0.1%),
addition of NaCl causes a slight reduction in
viscosity.
• At concentrations of Xanthan gum of 0.25% or
higher, addition of NaCl causes an increase in
viscosity.
• So the higher the Xanthan gum concentration,
the higher the concentration of salt required
to achieve maximum viscosity.
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22. • The Viscosity of Xanthan gum in aqueous
solutions is Pseudoplastic.
• Pseudoplastic means reduction of viscosity
when shear forces are applied.
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24. 2. Effect of Heat on properties of
Xanthan Gum
• Normal solutions show a decrease in the viscosity
when they are heated.
• Xanthan gum solutions show an increase in the
viscosity when they are heated, after an initial
decrease.
• Reason is transformation of a double helical
structure to a random coil which leads to increase
in the volume of the molecule.
• Xanthan gum solutions have excellent thermal
stability.
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26. 3. Effect of pH
• The viscosity of Xanthan gum solutions in the
presence of a low level of salt, 0.1% NaCl, is
independent of pH over the pH range 1.5-13
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28. Compatibility of Xanthan gum with
other solutions
• Dissolves directly in many acid solutions like
5% sulfuric acid, 5% Nitric acid, 5 % acetic
acid, 5% acetic acid, 10% Hydrochloric acid,
25% phosphoric acid.
• Solutions remains thermally stable at ambient
temperature for several months.
• Also compatible with methanol, ethanol,
isopropanol and acetone.
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29. • Enzymes like protease, cellulase,
hemicellulase, pectinase and amylase will not
degrade xanthan gum in solution.
• It can be degraded by strong oxidizing agents
like peroxides, persulfates and hypochlorites.
This degradation is elevated at high
temperatures.
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30. Interaction with Galactomannans
• Xanthan gum can also react with Guar Gum
and Locust bean gum.
• The viscosity of combination (Xanthan + Guar)
is greater than would be expected from the
individual viscosities.
• In the case of locust bean gum, the synergistic
viscosity increases at low gum concentration
but as the concentration of the gum is
increased, a heat reversible gel is formed.
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