The extraction of bacterial alginate from fermentation broths of Azotobacter vinelandii NCIMB 9068 as performed using crossflow filtration through ceramic membranes of varying nominal pore sizes (0.2-1.4 mum) The 1.4 mum membrane did not retain bacteria and was found inadequate for this application, For the other membranes, the permeation percentage and tile (viscometric) average molecular weight of filtered alginate increased with the membrane pore size, Membrane fouling was observed with all membranes hot decreased with the pore size. Therefore. the 0.8 mum membrane was selected for continuous alginate production in a membrane bioreactor. Alginate production was efficient for about 70 h. membrane fouling subsequently occurred. A total of 7.55 g of polysaccharide was recovered from the permeate. the production rate (0.09 g h(-1)), yield (0.21 g filtered alginate g(-1) sucrose), the volumetric productivity (0.014 g alginate dm(-3) h(-1)) and the specific productivity (0.022 alginate g(-1) cell h(-1)) being significantly higher than in the batch process. The average molecular weight of alginate varied over the production period to stabilize at a very low value (6 kDa) in the later phase of incubation.