Bacteriocins produced by microorganisms are a diverse and heterogeneous group of peptides with bacteriostatic and/or bactericidal activities. Over the past decade, bacteriocins have attracted considerable interest to represent an alternative food preservation technology [1]. Indeed, the use of bacteriocins in the food industry can help to reduce the addition of chemical preservatives as well as the intensity of heat treatments, resulting in foods which are more naturally preserved and richer in organoleptic and nutritional properties. This can be an alternative to satisfy the increasing consumers’ demands for safe and minimally-processed foods. One of the best characterized bacteriocins is nisin. This bacteriocin is produced by a group of Gram-positive bacteria that belongs to Lactococcus and Streptococcus species. Nisin is FDA (Food and Drug Administration) approved and has been widely used in the food industry as natural biopreservative for different types of foods. Commercial nisin is mainly produced by liquid fermentation. However the high cost compared with other chemical preservatives during the process has limited the commercial utilization of nisin in food industry. Indeed, the production of a commercial high quality nisin is affected by the high cost of downstream processing where it is often synonymous with chromatography, an efficient but expensive separation process in terms of capital and operational cost. To address this challenge, the alternatives of membrane processes, as separation methods were examined. Polyethersulfone (PES) membranes with nominal cut-offs of 10, 50 and 100 kDa were tested for ultrafiltration effectiveness. First, experiments were carried out with model solutions using commercially available nisin. The effect of transmembrane pressure and nisin concentration on the evolution over time of both permeate flux and nisin rejection was examined. The separation and concentration of nisin from fermentation broth were achieved using the above studied membranes. Nisin isolation using ultrafiltration was found to be effective, offering a realistic option towards the obtention of commercially available antimicrobial agents.