Structural investigation of an extracellular polysaccharide produced by the cariogenic bacterium Streptococcus mutans strain UA159

► Polysaccharide EPS159 contains 54% of α-1,6 linkages and 18% of α-1,3 linkages. ► A water-insoluble glucan predominantly α-1,6 linkages instead of α-1,3 linkages. ► A methylation procedure for polysaccharides insoluble in water and DMSO.