Polysaccharides – Xanthan Gum
M.Sc. Biotechnology Part II (Sem III)
Paper III - Unit III
Mumbai University
By: Mayur D. Ch...
Polysaccharides
• They are long chains of polymeric
carbohydrates.
• Monosaccharides are linked together by
Glycosidic bon...
Types of Polysaccharides
Storage
Acidic
Structural
Bacterial
3
1. Storage Polysaccharides
• Starch: Starch is glucose polymer in plants in
which glucopyranose units are bonded by alpha-...
2. Structural Polysaccharides
• Arabinoxylans: They are found in both the
primary and secondary cell walls of plants and
a...
• Chitin: Chitin is one of many naturally
occurring polymers and it forms a structural
component of many animals, such as
...
3. Acidic Polysaccharides
• Polysaccharides that contain carboxyl groups,
phosphate groups or sulfuric ester groups.
7
4. Bacterial Capsular Polysaccharides
• Pathogenic bacteria commonly produce a thick, mucous-
like, layer of polysaccharid...
Xanthan Gum
• Polysaccharide secreted by the bacterium
Xanthomonas campestris.
• Xanthomonas campestris was originally
iso...
X. Campestris
grown by using
carbohydrate as
substrate
X. Campestris
grown by using
Cabbage extracts
as substrate.
10
• Commercially produced Xanthan Gum was
identical to naturally produced Xanthan Gum.
• Essential requirements during the p...
• During fermentation, the pH of the medium
decreases due to the formation of metabolic
acids.
• Xanthan gum also has acid...
• Optimum temperature should be around 280 C
• Also at 1-5% glucose concentration has been
found to provide best xanthan g...
Structure of Xanthan Gum
• It is either a single or multi stranded helix
• It is a high molecular weight natural
polysacch...
15
Protocol
16
• Polysaccharide are precipitated by using
Isopropyl alcohol or acetone.
17
Properties of Xanthan Gum
• 1. Rheological Properties: Most important
property of Xanthan gum is to control the
rheologica...
19
• At low concentrations of Xanthan Gum (0.1%),
addition of NaCl causes a slight reduction in
viscosity.
• At concentration...
21
• The Viscosity of Xanthan gum in aqueous
solutions is Pseudoplastic.
• Pseudoplastic means reduction of viscosity
when sh...
23
2. Effect of Heat on properties of
Xanthan Gum
• Normal solutions show a decrease in the viscosity
when they are heated.
•...
25
3. Effect of pH
• The viscosity of Xanthan gum solutions in the
presence of a low level of salt, 0.1% NaCl, is
independent...
27
Compatibility of Xanthan gum with
other solutions
• Dissolves directly in many acid solutions like
5% sulfuric acid, 5% Ni...
• Enzymes like protease, cellulase,
hemicellulase, pectinase and amylase will not
degrade xanthan gum in solution.
• It ca...
Interaction with Galactomannans
• Xanthan gum can also react with Guar Gum
and Locust bean gum.
• The viscosity of combina...
31
32
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Polysaccharides Xanthan gum & other examples

The following presentation is only for quick reference. I would advise you to read the theoretical aspects of the respective topic and then use this presentation for your last minute revision. I hope it helps you..!! Mayur D. Chauhan
Published on: Mar 4, 2016
Published in: Science      
Source: www.slideshare.net


Transcripts - Polysaccharides Xanthan gum & other examples

  • 1. Polysaccharides – Xanthan Gum M.Sc. Biotechnology Part II (Sem III) Paper III - Unit III Mumbai University By: Mayur D. Chauhan 1
  • 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. 2
  • 3. Types of Polysaccharides Storage Acidic Structural Bacterial 3
  • 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 4
  • 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. 5
  • 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. 6
  • 7. 3. Acidic Polysaccharides • Polysaccharides that contain carboxyl groups, phosphate groups or sulfuric ester groups. 7
  • 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. 8
  • 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. 9
  • 10. X. Campestris grown by using carbohydrate as substrate X. Campestris grown by using Cabbage extracts as substrate. 10
  • 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 11
  • 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. 12
  • 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 13
  • 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. 14
  • 15. 15
  • 16. Protocol 16
  • 17. • Polysaccharide are precipitated by using Isopropyl alcohol or acetone. 17
  • 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. 18
  • 19. 19
  • 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. 20
  • 21. 21
  • 22. • The Viscosity of Xanthan gum in aqueous solutions is Pseudoplastic. • Pseudoplastic means reduction of viscosity when shear forces are applied. 22
  • 23. 23
  • 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. 24
  • 25. 25
  • 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 26
  • 27. 27
  • 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. 28
  • 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. 29
  • 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. 30
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