Abstract: The invention relates to inorganic ultrafiltration or microfiltration membranes, which are modified by adsorbing on one of the faces of said membrane at least one hydrophilic polymer or copolymer, such as polyvinylpyrrolidone or polyvinylimidazole. The inorganic membrane can comprise a macroporous support coated with a microporous metal oxide layer, such as zirconia or alumina.These membranes (3) can be used in the ultrafiltration apparatus (1) for carrying out the separation of proteins such as proteins of latoserum, bovine serum albumin or lysozyme.