Native efflux pumps of Escherichia coli responsible for short and medium chain alcohol

Efflux pumps (EPs) are an important mechanism responsible for extrusion of toxic compounds from the cell. Engineering of microbial cell EPs is a promising strategy in the production of biofuels and chemicals. In this study, we evaluate the ability of 44 native Escherichia coli EPs to enhance tolerance to short and medium carbon chain alcohols (SMCAs). Among EPs studied, MdtJ, Bcr, and MdtH and YdeA transported the majority of tested monohydroxy, dihydroxy, and trihydroxy alcohols, respectively. Overexpression of MdtJ, Bcr, MdtH and YdeA increased the tolerance of strains to SMCAs by 35%-50%. The efficiency of EPs for transporting SMCAs was verified by use of the 1, 2, 4-butanetriol (BT) synthesis system: where overexpression of MdtH and YdeA effectively increased the titers of BT by 31% and 18.5%, respectively. This work demonstrates that the innate EP system of E. coli is a resource which might be exploited to improve the synthesis of biofuels and chemicals.