Engineered isoprenoid pathway enhances astaxanthin production in Escherichia coli

The isoprenoid pathway is a versatile biosynthetic network leading to over 23,000 compounds. Similar to other biosynthetic pathways, the production of isoprenoids in microorganisms is controlled by the supply of precursors, a mong other factors. To engineer a host that has the capability to supply ge ranylgeranyl diphosphate (GGPP), a common precursor of isoprenoids, we clon ed and overexpressed isopentenyl diphosphate (IPP) isomerase (encoded by id i) from Escherichia coil and GGPP synthase (encoded by gps) from the archae bacterium Archaeoglobus fulgidus. The latter was shown to be a multifunctio nal enzyme converting dimethylallyl diphosphate (DMAPP) to GGPP. These two genes and the gene cluster (crtBIYZW) of the marine bacterium Agrobacterium aurantiacum were introduced into E. coli to produce astaxanthin, an orange pigment and antioxidant. This metabolically engineered strain produces ast axanthin 50 times higher than values reported before. To determine the rate -controlling steps in GGPP production, the IDI-GPS pathway was compared wit h another construct containing idi, ispA (encoding farnesyl diphosphate (FP P) synthase in E. coli), and crtE (encoding GGPP synthase from Erwinia ured ovora). Results show that the conversion from FPP to GGPP is the first bott leneck, followed sequentially by IPP isomerization and FPP synthesis. Remov al of these bottlenecks results in an E. coil strain providing sufficient p recursors for in vivo synthesis of isoprenoids. (C) 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 235-241, 1999.