Heterologous Protein Expression by Lactococcus lactis

This chapter describes the use of Lactococcus lactis as a safe and efficient cell factory to produce heterologous proteins of medical interest. The relevance of the use of this lactic acid bacterium (LAB) is that it is a noncolonizing, nonpathogenic microorganism that can be delivered in vivo at a mucosal level. The use of strains of L. lactis in clinical trials in humans to alleviate inflammatory bowel diseases has opened up the possibility of using this same LAB to target other diseases. Several crucial aspects are addressed in this chapter, such as the expression of heterologous protein, subcellular compartment into which the heterologous protein is located, and description of a standardized protocol to process samples in cell and cell-free fractions to detect the targeted protein expressed by L. lactis.