Using a methodology based on the combination of recently developed parameter scanning ultrafiltration with carrier phase ultrafiltration (CPUF), this article examines the separation of lysozyme directly from natural chicken egg white (CEW) solutions with 30 kDa membranes. The suitability of two membranes, i.e. Biomax 30 kDa polyethersulfone and Ultracel Amicon YM 30 kDa regenerated cellulose membranes were rapidly assessed and the physicochemical conditions likely to be optimal were identified by parameter scanning ultrafiltration. Under Suitable conditions, with the Biomax 30 kDa membrane, lysozyme transmission from the CEW solution Could be more than 80% and the lysozyme purity obtained in permeate was greater than 94% after one stage Ultrafiltration process. (c) 2005 Elsevier B.V. All rights reserved.