Preparation of low ultra-filtration membranes, by cross-flow filtration of a protein solution on an a-alumina macroporous ceramic support (0.2 mu m SCT membrane) and further tanning/drying treatments, has been improved. The new operational procedure cut the total manufacturing duration from 5 h according to previous authors down to only a couple of hours. A study of the effect of the protein/tanning agent couple shows that the best performance is obtained with membranes built from proteins having a large molecular weight distribution and then tanned with formaldehyde solution. The optimal concentration of the cross-linking agent depends on the kind of protein used.