Improvement of lycopene biosynthesis in waaC and waaF mutants of Escherichia coli by integrant expression of crtEBI gene and deletion of aceE and gdhA

Abstract

As a bright red carotenoid pigment found in tomatoes and other red fruits, lycopene was efficiently produced by Escherichia coli transformed with the genes involving in lycopene biosynthesis. Our previous work showed that E. coli ΔwaaC and ΔwaaF with higher permeability of outer membrane were better chassis for lycopene biosynthesis. However, further work needed to improve lycopene synthesis in the aforementioned strains. In the current study, the exogenous crtEBI genes from C. glutamicum 14067 were first integrated into the chromosome of ΔwaaC and ΔwaaF. Compared to ΔwaaC/pWSK29-crtEBI and ΔwaaF/pWSK29-crtEBI (4.19 and 4.20 mg/g lycopene respectively), ΔwaaC lacZ::crtEBI (CWC01) and ΔwaaF lacZ::crtEBI (CWF01) produced higher lycopene levels at 16.14 mg/g and 15.81 mg/g, respectively. Later, the individual and combinational deletion of aceE and gdhA was conducted in CWC01 and CWF01, respectively. The double knock-out strains CWC04 and CWF04 showed the improved yield at 19.65 mg/g and 22.24 mg/g, respectively. Finally, the four genes involving in MEP pathway (dxs, dxr, ispA and idi) were further overexpressed. The highest lycopene yield was achieved at 25.82 mg/g by CWF04/pACYC184-dxsE289G-dxrK37N,K217N-ispA-idi. The current study showed that E. coli ΔwaaC and ΔwaaF were optimal chassis for ambitious metabolic modification to produce lycopene.