초록
<P><B>Abstract</B></P> <P>ω-Hydroxy palmitic acid (ω-HPA) is a valuable compound for an ingredient of artificially synthesized ceramides and an additive for lubricants and adhesives. Production of such a fatty acid derivative is limited by chemical catalysis, but plausible by biocatalysis. However, its low productivity issue, including formations of unsaturated fatty acid (UFA) byproducts in host cells, remains as a hurdle toward industrial biological processes. In this study, to achieve selective and high-level production of ω-HPA from glucose in <I>Escherichia coli</I>, FadR, a native transcriptional regulator of fatty acid metabolism, and its regulon were engineered. First, FadR was co-expressed with a thioesterase with a specificity toward palmitic acid production to enhance palmitic acid production yield, but a considerable quantity of UFAs was also produced. In order to avoid the UFA production caused by <I>fadR</I> overexpression, FadR regulon was rewired by i) mutating FadR consensus binding sites of <I>fabA</I> or <I>fabB</I>, ii) integrating <I>fabZ</I> into <I>fabI</I> operon, and iii) enhancing the strength of <I>fabI</I> promoter. This approach led to dramatic increases in both proportion (48.3–83.0%) and titer (377.8 mg/L to 675.8 mg/L) of palmitic acid, mainly due to the decrease in UFA synthesis. Introducing a fatty acid ω-hydroxylase, CYP153A35, into the engineered strain resulted in a highly selective production of ω-HPA (83.5 mg/L) accounting for 87.5% of total ω-hydroxy fatty acids. Furthermore, strategies, such as i) enhancement in CYP153A35 activity, ii) expression of a fatty acid transporter, iii) supplementation of triton X-100, and iv) separation of the ω-HPA synthetic pathway into two strains for a co-culture system, were applied and resulted in 401.0 mg/L of ω-HPA production. For such selective productions of palmitic acid and ω-HPA, the rewiring of FadR regulation in <I>E. coli</I> is a promising strategy to develop an industrial process with economical downstream processing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FadR regulon was rewired by mutating FadR binding sites of promoters. </LI> <LI> Rewiring FadR regulation decreased the degree of unsaturation from 33.4% to 5.9% in free fatty acid profile. </LI> <LI> Co-culture system enhanced productivity by relieving the possible metabolic burden. </LI> <LI> In total, 401.0 mg/L of ω-hydroxy palmitic acid was produced in high percentages. </LI> </UL> </P>