Recovery and purification of the exopolysaccharide PS-EDIV from Sphingomonas pituitosa DSM 13101

The separation and purification of the exopolysaccharide PS-EDIV from the culture broth of Sphingomonas pituitosa DSM 13101 was studied. For this purpose a sequence of separation and concentration operations including centrifugation, ultrafiltration and precipitation were used. Cell removal by centrifugation was performed at four different temperatures, showing that at 40 °C clarification was best with a residual biomass concentration of 0.1 g L−1. Subsequently ultrafiltration tests revealed that the cell debris containing polysaccharide solution did not cause any membrane fouling. The observed decrease of permeate flux at high PS-EDIV concentrations was rather attributed to a concentration polarization effect. The polymer solution could be concentrated up to 5 g L−1 whereby 90% of the initial polymer was recovered. In a last recovery step the polymer was precipitated using four different organic solvents: acetone, ethanol, propanol and isopropanol. Isopropanol gave the highest precipitation yield of 81% at a solvent ratio of 9:1 (v/v).