Production and applications of microbial exopolysaccharides N-acetyl-D-glucosamine(an amino sugar); · D-glucuronic acid The presence of uronic acids in microbial exopolysaccharides results in their oolyanionic nature In addition to one or more sugars, exopolysaccharides from prokaryotes commonly contain pyruvate ketals and various ester-linked organic substituents. These are only rarely found in eukaryotic exopolysaccharides pyruvate Pyruvate ketals add to the anionic nature of the exopolysaccharide and are usually ketals present in stoichiometric ratios with the carbohydrate component. Pyruvate is normally attached to the neutral hexoses but may also be attached to uronic acids. In the absence of uronic acids, pyruvate alone contributes to the anionic nature of the acetate Acetate is the commonest ester-linked component of exopolysaccharides and does not contribute to their anionic nature. Less common ester- linked components, which may be found along with acetate in some exopolysaccharides, include propionate; e succinate . 3-hydroxybutanoate organic acids The presence of organic acid substituents in exopolysaccharides increases the pophilicity of the molecule. In addition, for some exopolysaccharides with relatively amino ada high organic acid contents their interaction with cations and with other polysaccharides may be influenced. Several amino acids have also been found in bacterial exopolysaccharides, including serine and L-glutamic acid(Figure 7.1 phosphate and Some microbial exopolysaccharides contain the inorganic substituents phosphate and sulphate sulphate. Phosphate has been found in exopolysaccharide from bacteria of medical importance, including Escherichia coli Sulphate is far less common than phosphate and has only been found in species of cyanobacteria. In addition to these inorganic components, which form part of the structure of some exopolysaccharides, all polyanionic polymers will bind a mixture of cations Exopolysaccharides are, therefore, purified in the salt form. The strength of binding of the various cations depend on the exopolysaccharide; some bind the divalent cations calcium, barium and strontium very strongly, whereas others prefer certain monovalent cations, eg NaProduction and applications of microbial exopolysaccharides 1 97 polyanionic nature pyrwate htals acetate organicacids amino acids phosphate and sulphate N-acetyl-D-glucosamine (an amino sugar); D-glucuronic acid; D-galacturonic acid. The presence of uronic acids in microbial exopolysaccharides results in their polyanionic nature. In addition to one or more sugars, exopolysaccharides from prokaryotes commonly contain pyruvate ketals and various ester-linked organic substituents. These are only rarely found in eukaryotic exopolysaccharides. Pyruvate ketals add to the anionic nature of the exopolysaccharide and are usually present in stoichiometric ratios with the carbohydrate component. Pyruvate is nody attached to the neutral hexoses but may also be attached to uronic acids. In the absence of uronic acids, pyruvate alone contributes to the anionic nature of the exopolysaccharide. Acetate is the commonest ester-linked component of exopolysaccharides and does not contribute to their anionic nature. Less common ester-linked components, which may be found along with acetate in some exopolysaccharides, include: propionate; glycerate; succinate; 3-hydroxybutanoate. The presence of organic acid substituents in exopolysaccharides increases the lipophilicity of the molecule. In addition, for some exopolysaccharides with relatively high organic acid contents, their interaction with cations and with other polysaccharides may be influenced. Several amino acids have also been found in bacterial exopolysaccharides, including serine and L-glutamic acid (Figure 7.1). Some microbial exopolysaccharides contain the inorganic substituents phosphate and sulphate. Phosphate has been found in exopolysaccharide from bacteria of medical importance, including Escherichia coli. Sulphate is far less common than phosphate and has only been found in species of cyanobacteria. In addition to these inorganic components, which form part of the structure of some exopolysaccharides, all polyanionic polymers will bind a mixture of cations. Exopolysaccharides are, therefore, purified in the salt form. The strength of binding of the various cations depend on the exopolysaccharide; some bind the divalent cations calcium, barium and strontium very strongly, whereas others prefer certain monovalent cations, eg Na