Cellulose membrane produced by the bacterium Acetobacter xylinum was deproteinated and investigated for pervaporation (PV) of binary water-ethanol mixtures. The membrane was characterised using elemental analysis, infra-red spectroscopy, scanning electron microscopy as well as for mechanical strength and sorption characteristics. A batch stirred cell was used to study the PV behaviour of water-ethanol mixtures through the membrane. The permeate flux, selectivity, PV separation index (PSI), solubility and degree of sorption were studied as a function of increasing ethanol concentration in the feed. The membrane was found highly selective to water. Even when the feed was rich in ethanol (> 70% (w/w)) the permeate contained higher than 95% (w/w) of water. For feed compositions containing less than 30% water, the selectivity towards water was in the range of 125-287, the flux was greater than 100 g/m(2) h and PSI was of the order of 10(4) g/m(2) h. (C) 2002 Elsevier Science B.V. All rights reserved.