Natural and engineered promoters for gene expression in Lactobacillus species.

Lactobacillus species are attractive hosts for the expression of heterologous proteins, antigens, vaccines, and drugs due to their GRAS (generally recognized as safe) status. The bioengineering techniques open new possibilities of improving Lactobacillus strains. In this regard, the control of the gene expression in Lactobacillus strains through the adequate native or engineered promoters acquires a key role in the development of biotechnological applications and for their function as probiotic bacteria. Depending on the objective sought, the protein produced and the strain used, inducible or constitutive promoters can be chosen. Whereas, when a fine-tuning of gene expression is required, the development of synthetic promoter libraries could be the best approach. In this work, we revise the main constitutive and inducible natural promoters from Lactobacillus strains or from other genus that have been applied in Lactobacillus, as well as the few engineered promoters developed for these bacteria.