A new and efficient method for the purification of levansucrase from cell-free extracts of a flocculant mutant: of Zymomonas mobilis ATCC 10988 was developed. Levansucrase activity was almost completely recovered and purified by a factor of 15 after precipitation with 0.1 M MnCl2 as a first capturing step. The enzyme was homogeneously purified by ultrafiltration and anion-exchange chromatography and exhibited a levan-forming activity of 39.2 U mg(-1). The native enzyme formed large aggregates with an apparent molecular mass of more than 10(6) Da as determined by size-exclusion chromatography, whereas denaturing SDS-PAGE indicated an apparent molecular mass of 50 kDa for the subunits.