Method for removal of impurities from bacterial capsular polysaccharide based preparations

The present invention relates to an improved process for purification of bacterial capsular polysaccharides, more specifically capsular polysaccharides of gram negative bacteria. The process comprises of concentration and dia filtration of harvest, treatment with anionic detergent and strong alkali followed by centrifugation, diafiltration and cationic detergent based precipitation of bacterial polysaccharides. The process results in significant reduction of endotoxin, protein and nucleic acid impurities thereby providing higher recovery of capsular polysaccharide with the desired O-acetyl levels. Said process is scalable, non-enzymatic, and employs fewer purification steps.