Xanthan 6-acetyl-mannose

Xanthan (Figure 11) is a commercially important polysaccharide produced by the bacterium Xanthomonas campestris.187 188 The xanthan backbone consists of a P(l-4)-linked D-glucopyranose chain with a trisaccharide side chain attached at C3 to alternate glucose residues. These side chains consist of an acetylated mannose residue, a glucuronic acid residue, and a pyruvate ketal linked to a terminal mannose residue. The acetate and pyruvate content depend on the fermentation and isolation conditions used by the supplier. 

Figure 14 Partial structure of xanthan gum showing P-D-(l,4)-glucose, 10, acetylated P-d-(1,2)-mannose, 11, P-D-(l,4)-glucuronic acid, 12, and pyruvic acid terminated P-D-mannose, 13. 

Xanthan gum can be regarded as a cellulose derivative. The main chain consists of 1,4 linked P-glucopyranose residues. On an average, every second glucose residue bears in the 3-position a trisaccharide of the structure P-D-Man/ -(1 4)-P-d-G1c/ A(1 2)-a-D-Man/7 as the side chain. The mannose bound to the main chain is acetylated in position 6 and ca. 50% of the terminal mannose residues occur ketahzed with pyruvate as 4,6-0-(l-carboxyethylidene)-D-mannopyranose (cf. Formula 4.162 GlcpA glucuronic acid). 

Xanthan Xanthomonas spp. Glucose, Sucrose, Glucose-syrup, Whey D-Glucose, D-Mannose, D-Glucuronic acid, Acetyl Pyruvate... 

---