BACKGROUND: Lipases are commercially important enzymes, and the development and optimization of their production processes are of great interest. The diversity of behaviours between strains stresses the need for research on this topic, especially when bioreactor culture is considered. The study of a continuous operating mode is especially attractive, since very scarce information is available on its application to microbial lipases production. RESULTS: Lipase production in submerged cultures of Yarrowia lipolytica CECT 1240 (ATCC 18942) has been investigated. Significant lipolytic activity (over 700 U dm(-3)), mostly extracellular and membrane-bound, was obtained in shake flasks using medium supplemented with olive oil. The culture was carried out in air-lift and stirred tank bench-scale bioreactors and the latter was selected. The influence of aeration and agitation rates was assessed in batch cultures, and agitation from 400-700 rpm and low aeration rates (i.e. 0.2 vvm) are recommended. Batch, fed-batch and continuous operation were investigated, and regular enzyme production (up to 600 U dm(-3)) was achieved with the latter. CONCLUSION: Lipase production by the selected strain was successfully carried out in shake flasks and bench-scale bioreactors. After studying batch, fed-batch and continuous processes, continuous culture in a stirred tank bioreactor was found best in terms of regular enzyme production, exceptionally good operational stability and good fitting of the results to mathematical models. (C) 2009 Society of Chemical Industry