The solution molecular weight and shape of the bacterial exopolysaccharides amylovoran and stewartan

Amylovoran, the acidic exopolysaccharide (EPS) of Erwinia amylovora, and stewartan, the capsular EPS of E. stewartii, were characterized by analytical ultracentrifugation and by size exclusion chromatography connected to dual detection of light scattering and mass. The average molecular weights of amylovoran and stewartan were determined as 1.0 x 10(6) and 1.7 x 10(6) Da, with polydispersity values (Mw/M(n)) of 1.5 and 1.4, respectively. Based on the sugar composition and their molecular weight, both exopolysaccharides consist of approximately 1000 repeating units per molecule, this suggests a similar mechanism for chain length determination during biosynthesis of EPS in both organisms.