The interaction between medium components, microorganisms and the operational mode to produce lipase by Candida rugosa was studied. It has been observed as an emulsion formation between oleic acid and urea during continuous culture. Because of this emulsion, the nitrogen source cannot be assimilated by the cells. The lack of nitrogen source provoked a decrease in protein synthesis, being lipase synthesis suppressed. The change of the nitrogen source from urea to ammonium sulfate avoided the emulsion formation, allowing to reach biomass and lipase steady states in continuous cultures. In batch cultures, no effect of nitrogen source on lipase production and biomass was observed. The specific productivity in continuous culture was slightly higher than in batch cultures.