초록
<P><B>Background</B></P><P>Plasmid-based overexpression of genes has been the principal strategy for metabolic engineering. However, for biotechnological applications, plasmid-based expression systems are not suitable because of genetic instability, and the requirement for constant selective pressure to ensure plasmid maintenance.</P><P><B>Results</B></P><P>To overcome these drawbacks, we constructed an <I>Escherichia coli</I> lycopene production strain that does not carry a plasmid or an antibiotic marker. This was achieved using triclosan-induced chromosomal evolution, a high gene copy expression system. The engineered strain demonstrated high genetic stability in the absence of the selective agent during fermentation. The replacement of native <I>appY</I> promoter with a T5 promoter, and the deletion of the <I>iclR</I> gene in <I>E. coli</I> CBW 12241 further improved lycopene production. The resulting strain, <I>E. coli</I> CBW 12241(<I>Δ</I><I>iclR</I>, P<SUB>T5</SUB>-<I>appY</I>), produced lycopene at 33.43 mg per gram of dry cell weight.</P><P><B>Conclusions</B></P><P>A lycopene hyper-producer <I>E. coli</I> strain that does not carry a plasmid or antibiotic marker was constructed using triclosan-induced chromosomal evolution. The methods detailed in this study can be used to engineer <I>E. coli</I> to produce other metabolites.</P>