초록
<P><B>Abstract</B></P> <P>Chemicals production by engineered microorganisms often requires induction of target gene expression at an appropriate cell density to reduce conflict with cell growth. The <I>lux</I> system in <I>Vibrio fischeri</I> is a well-characterized model for cell density-dependent regulation of gene expression termed quorum sensing (QS). However, there are currently no reports for application of the <I>lux</I> system to microbial chemical production. Here, we constructed a synthetic <I>lux</I> system as a tunable cell density sensor-regulator using a synthetic <I>lux</I> promoter and a positive feedback loop in <I>Escherichia coli</I>. In this system, self-induction of a target gene expression is driven by QS-signal, and its threshold cell density can be changed depending on the concentration of a chemical inducer. We demonstrate auto-redirection of metabolic flux from central metabolic pathways toward a synthetic isopropanol pathway at a desired cell density resulting in a significant increase in isopropanol production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A synthetic lux system as a tunable cell density sensor-regulator using a synthetic lux promoter and a positive feedback loop in <I>Escherichia coli</I> was constructed. </LI> <LI> Self-induction of a target gene expression is driven by QS-signal, and its threshold cell density can be changed depending on the concentration of a chemical inducer. </LI> <LI> Auto-redirection of metabolic flux from central metabolic pathways toward a synthetic isopropanol pathway at a desired cell density resulted in 3- and 2-fold increase in isopropanol production titer and yield. </LI> </UL> </P>