The complex preparation ethapolan synthesized by Acinetobacter sp. consists of neutral (minor component) and two acidic exopolysaccharides (EPS) one of which is acylated. On the basis of chemical modification of EPS, solvolysis with anhydrous hydrogen fluoride resulting in a penta- and octasaccharide fragments, Smith degradation, 1H- and 13C NMR analysis the following structure of the acylated polysaccharide repeating unit has been established (scheme): It is suggested that in the acylated EPS at least one glucose residue and the galactose residue are O-acylated.