BACKGROUND: Ceramic membranes have received more attention than polymeric membranes for the separation and purification of bio-products owing to their superior chemical, mechanical and thermal properties. Commercially available ceramic membranes are too expensive. This could be overcome by fabricating membranes using low-cost raw materials. The aim of this work is to fabricate a low-cost gamma-Al2O3-clay composite membrane and evaluate its potential for the separation of bovine serum albumin (BSA) as a function of pH, feed concentration and applied pressure. To achieve this, the membrane support is prepared using low-cost clay mixtures instead of very expensive alumina, zirconia and titania materials. The cost of the membrane can be further reduced by preparing a gamma-alumina surface layer on the clay support using boehmite sol synthesized from inexpensive aluminium chloride instead of expensive aluminium alkoxide using a dip-coating technique. RESULTS: The pore size distribution of the gamma-Al2O3-clay composite membrane varied from 5.4-13.6 nm. The membrane was prepared using stable boehmite sol of narrow particle size distribution and mean particle size 30.9 nm. Scanning electron microscopy confirmed that the surface of the gamma-Al2O3-clay composite membrane is defect-free. The pure water permeability of the support and the composite membrane were found to be 4.838 x 10(-6) and 2.357 x 10(-7) m(3) m(-2) s(-1) kPa(-1), respectively. The maximum rejection of BSA protein was found to be 95%. It was observed that the separation performance of the membrane in terms of flux and rejection strongly depends on the electrostatic interaction between the protein and charged membrane. CONCLUSION: The successively prepared gamma-Al2O3-clay composite membrane proved to possess good potential for the separation of BSA with high yield and could be employed as a low cost alternate to expensive ceramic membranes. (C) 2009 Society of Chemical Industry