A system for controlled targeting of heterologous protein was developed in the food-grade bacterium Lactococcus lactis. It is composed of the L. lactis strain NZ9000 and of two broad host range expression vectors pCYT:Nuc and pSEC:Nuc for, respectively, cytoplasmic and secreted staphylococcal nuclease (Nuc) nisin-inducible production. The level of intracellular production of Nuc measured with pCYT:Nuc (3 mg l - 1 ) is significantly lower than the one obtained with pSEC:Nuc (~20 mg l - 1 ). The secretion efficiency (SE) of Nuc is estimated to be ~70%, corresponding to ~15 mg of secreted Nuc l - 1 . Furthermore, we established that Nuc production continued in L. lactis 10 h after a 1-h nisin-pulse induction. This system was then used for intra- and extracellular production of a protein of therapeutical interest in L. lactis, the ovine interferon-omega (IFN-ω). The SE and the quantity of secreted active IFN-ω were evaluated respectively to be ~70% and ~1 mg l - 1 (~two-fold higher than the cytoplasmic form).