초록
<P><B>Abstract</B></P> <P>Microorganisms can be engineered to produce a variety of biofuels and commodity chemicals. The accumulation of these products, however, is often toxic to the cells and subsequently lowers production yields. Efflux pumps are a natural mechanism for alleviating toxicity through secretion of the product; unfortunately, pump overexpression also often inhibits growth. Tuning expression levels with inducible promoters is time-consuming and the reliance on small-molecule inducers is cost-prohibitive in industry. We design an expression regulation system utilizing a native <I>Escherichia coli</I> stress promoter, P<SUB>gntK</SUB>, to provide negative feedback to regulate transporter expression levels. We test the promoter in the context of the efflux pump AcrB and its butanol-secreting variant, AcrBv2. P<SUB>gntK</SUB>-driven AcrBv2 confers increased tolerance to <I>n</I>-butanol and increased titers of <I>n</I>-butanol in production. Furthermore, the system is responsive to stress from toxic overexpression of other membrane-associated proteins. Our results suggest a use for feedback regulation networks in membrane protein expression.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A genetic network that optimizes membrane protein expression is created in <I>E. coli</I>. </LI> <LI> Controlling expression of a butanol-secreting pump gives higher n-butanol titers. </LI> <LI> The system is tunable and generalizable to other toxic membrane proteins. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>