生物
代谢工程
基因
大肠杆菌
质粒
营养不良
报告基因
类胡萝卜素
可选择标记
分子生物学
遗传学
基因表达
生物化学
作者
Luke Z. Yuan,Pierre E. Rouvière,Robert A. LaRossa,Won-Chul Suh
标识
DOI:10.1016/j.ymben.2005.08.005
摘要
For metabolic engineering it is advantageous in terms of stability, genetic regulation, and metabolic burden to modulate expression of relevant genes on the chromosome rather than relying on over-expression of the genes on multi-copy vectors. Here we have increased the production of beta-carotene in Escherichia coli by replacing the native promoter of the chromosomal isoprenoid genes with the strong bacteriophage T5 promoter (P(T5)). We recombined PCR fragments with the lambda-Red recombinase to effect chromosomal promoter replacement, which allows direct integration of a promoter along with a selectable marker that can subsequently be excised by the Flp/FRT site-specific recombination system. The resulting promoter-engineered isoprenoid genes were combined by serial P1 transductions into a host strain harboring a reporter plasmid containing beta-carotene biosynthesis genes allowing a visual screen for yellow color indicative of beta-carotene accumulation. Construction of an E. coli P(T5)-dxs P(T5)-ispDispF P(T5)-idi P(T5)-ispB strain resulted in producing high titers (6mg/g dry cell weight) of beta-carotene. Surprisingly, over-expression of the ispB gene, which was expected to divert carbon flow from the isoprenoid pathway to quinone biosynthesis, resulted in increased beta-carotene production. We thus demonstrated that chromosomal promoter engineering of the endogenous isoprenoid pathway yielded high levels of beta-carotene in a non-carotenogenic E. coli. The high isoprenoid flux E. coli can be used as a starting strain to produce various carotenoids by introducing heterologous carotenoid genes.
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