[Modulation of isoprenoid gene expression with multiple regulatory parts for improved beta-carotene production]

Strong promoters might not be optimal to obtain maximum metabolic flux towards desired products, whereas modulating gene expression with multiple regulatory parts is an option to obtain optimal expression strength. Therefore, we assessed the difference of impact on beta-carotene production between modulating isoprenoid gene expression with multiple regulatory parts and strong promoter, to improve beta-carotene production through combined modulation of essential isoprenoid genes. Eight isoprenoid genes were modulated with six artificial regulatory parts having a wide range of strengths to assess their effects on beta-carotene production. Optimal strength for each isoprenoid gene expression was identified, leading to 1.2 to 3.5-fold increase in beta-carotene production. In contrast to previous reports, our work suggests that modulating dxr, ispG and ispH genes with appropriate strengths increase beta-carotene production. Beta-carotene yield reached 17.59 mg/g after combined modulation of dxs and idi genes, 8-fold higher than that of the parent strain. Modulating gene expression with multiple regulatory parts was better than strong promoter, providing a new gene modulation strategy for targeted biosynthesis.