Heterologous Protein Production in Lactobacillus (plantarum) Using pSIP Vectors

While lactobacilli are not generally regarded as efficient cell factories for heterologous proteins, these food-grade Gram-positive bacteria are attractive as expression hosts for medicinal proteins. Furthermore, tools have been developed not only to secrete the protein of interest, but also to anchor the protein to the cell membrane or the cell wall. Research efforts aimed at the production and surface display of complex vaccine proteins have shown that lactobacilli are capable of producing heterologous proteins that are otherwise difficult to produce in soluble form. Many recent studies on expressing a wide variety of proteins in lactobacilli have employed the pSIP vector system, which offers a wide range of possibilities for inducible expression, including various options for secretion and surface anchoring. The modular nature of the pSIP vectors allows for rapid screening of multiple expression strategies. This chapter describes the pSIP vector system and how it can be used to accomplish protein expression in lactobacilli.