Recently, we developed a method for the selective extracellular accumulation of recombinant proteins using an autotransporter secretion pathway. This technology involves engineering of the Pet autotransporter protein to allow secretion of a protein of interest into the culture medium. In this work we report how the platform can be exploited for the production of an ETEC protein vaccine candidate. This production system offers a valid alternative to other traditional methods for production of “difficult” proteins with comparable results in terms of purity and protein conformational stability thus having a simplified and cost effective downstream process. The antigen production using the Pet autotransporter system has been scaled for the first time up to a fermentation level, obtaining up to 29 mg of antigen produced per litre of culture supernatant. Taken together these findings suggest the suitability of the system for further industrial applications.