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Kim, Eun-Mi,Woo, Han Min,Tian, Tian,Yilmaz, Suzan,Javidpour, Pouya,Keasling, Jay D.,Lee, Taek Soon Academic Press 2017 Metabolic engineering Vol.44 No.-
<P><B>Abstract</B></P> <P>Inducible gene expression systems are widely used in microbial host strains for protein and commodity chemical production because of their extensive characterization and ease of use. However, some of these systems have disadvantages such as leaky expression, lack of dynamic control, and the prohibitively high costs of inducers associated with large-scale production. Quorum sensing (QS) systems in bacteria control gene expression in response to population density, and the LuxI/R system from <I>Vibrio fischeri</I> is a well-studied example. A QS system could be ideal for biofuel production strains as it is self-regulated and does not require the addition of inducer compounds, which reduce operational costs for inducer. In this study, a QS system was developed for inducer-free production of the biofuel compound bisabolene from engineered <I>E. coli</I>. Seven variants of the Sensor plasmid, which carry the <I>luxI</I>-<I>luxR</I> genes, and four variants of the Response plasmid, which carry bisabolene producing pathway genes under the control of the P<SUB> <I>luxI</I> </SUB> promoter, were designed for optimization of bisabolene production. Furthermore, a chromosome-integrated QS strain was engineered with the best combination of Sensor and Response plasmid and produced bisabolene at a titer of 1.1g/L without addition of external inducers. This is a 44% improvement from our previous inducible system. The QS strain also displayed higher homogeneity in gene expression and isoprenoid production compared to an inducible-system strain.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A quorum-sensing host was developed for inducer-free biofuel production in <I>E. coli</I>. </LI> <LI> Systematic engineering of the quorum-sensing system generated efficient QS hosts. </LI> <LI> Chromosomal integration of QS system generated a versatile inducer-free platform. </LI> <LI> The QS integrated strain produced a biofuel at higher yields than inducible system. </LI> <LI> QS system confirms higher homogeneity in gene expression and isoprenoid production. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>