Acid hydrolysis and quantitative determination of total hexosamines of an exopolysaccharide produced by Citrobacter sp.

During the hydrolysis of an exopolysaccharide (EPS) produced by Citrobacter sp., the maximum liberation of hexosamine was obtained with 6 M HCl at 115 degrees C in an autoclave for 1 h. The glycosidic bond energy and degree of acetylation of the hexosamine in EPS were approximately 77 kJ mol(-1) and 61%, respectively. Thermal destruction of the hexosamines and the effect of salt on the hexosamine determination could be minimized under the optimized hydrolytic conditions. Using a modified Elson-Morgan method, maximum total hexosamine concentration was determined to be 3.2 g l(-1) (29% of crude EPS) after 96 h of fed-batch culture.