Improving medium chain fatty acid production in Escherichia coli by multiple transporter engineering

Medium-chain fatty acids (C-6-C-10, MCFAs) represent valuable molecules for food and pharmaceutical industries. However, MCFAs in Escherichia coli induce stresses and toxicity, reducing final yields. These phenotypes could be alleviated if MCFA export from cells was accelerated, yet information on proteins responsible for exporting MCFAs remains limited. Here, a panel of 17 genes or operons was screened. Overexpressing resistance nodulation cell division family transporter acrE, mdtE and mdtC increased MCFA titer by 46.4%, 65.2% and 33.8%, whereas overexpressing transcriptional activators soxS, marA and multidrug efflux pumps cmr, fadL decreased MCFA titer by 42.5%, 27.8%, 37.6% and 29.5%, respectively. Furthermore, the effect of multiple transporter engineering was investigated. Overexpressing acrE, mdtE and mdtC together with deleting cmr increased MCFA production by more than two-fold. This study demonstrated the efficient efflux pump specifically for MCFAs and this multiple transporter engineering strategy can be employed to synthesize other bio-products toxic to microorganisms.