During ethanol fermentation with in situ pervaporation, membrane fouling might occur due to polymers originating from yeast cell lysis. The aim of this study was to evaluate the influence of yeast cellular polymers on pervaporative membrane performance. Lipids were identified as the most detrimental components among these cellular polymers causing 50% and 33% flux decrease in polydimethylsiloxane (PDMS) and polyoctylmethylsiloxane (POMS) membranes, respectively. This fouling was irreversible and might be due to hydrophobic interactions between lipids and membranes resulting in high lipid adsorption on membrane surface. The relatively hydrophobic model protein BSA also contributed to flux decrease in PDMS membrane but RNA and the model polysaccharide glycogen did not. The PDMS membrane selectivity for ethanol/water remained similar to 4.5 in all cases. All the cellular components decreased the water flux through the POMS membrane. However, the ethanol flux through the membrane was not altered very much, resulting in increased membrane selectivity. (C) 2012 Elsevier Ltd. All rights reserved.