The present invention relates to a method for removing impurities from biopolymer material, e.g. polysaccharides, polypeptides or polynucleotides. More particularly, the present invention provides a method of reducing lipopolysaccharide levels in a lipopolysaccharide containing biopolymer material, comprising the successive steps of: a) providing an aqueous solution containing 0.05-50 wt. % of dissolved lipopolysaccharide-containing biopolymer material; 0.001-10 wt.% of a surfactant; 0.05-15 wt. % of solid adsorbent; and at least 50 wt. % of water; b) allowing the adsorbent to adsorb lipopolysaccharides; c) separating the solid adsorbent containing adsorbed lipopolysaccharides from the remaining aqueous solution; and d) recovering the biopolymer material containing a reduced level of lipopolysaccharide from the separated aqueous solution.