P136: Metabolic engineering of Escherichia coli for retinoids production

Retinoids are lipophilic isoprenoids molecules, which are defined as a class of chemical compounds that are related chemically to vitamin A. Retinoids, being derived from ß-carotene, consist of a cyclic group and a linear chain with hydrophilic end group. Retinoids include retinol, retinal, retinoic acid, and retinyl esters, and also exist in other various structures differentiated by their functional groups. Carotenoids including ß-carotene, precursor of retinoids, are derived from isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) which are common five-carbon building blocks of all isoprenoids. Generally, IPP and DMAPP are synthesized from 2-C-methyl-D-erythritol-4-phosphate (MEP) and mevalonate (MVA) pathway in prokaryotes and eukaryotes, respectively. For supplementation of IPP and DMAPP, dxs gene encoding DXP synthase, the rate-limiting step of MEP pathway, was overexpressed, and the optimized MVA pathway was introduced to E. coli. The expression of the five exogenous genes encoding GGPP synthase (crtE), phytoene synthase (crtB), phytoene desaturase (crtI), lycopene cyclase (crtY), ß-carotene 15,15’-mono(di)oxygenase (BCM(D)O) can make E. coli to produce retinoids from IPP and DMAPP. To prevent intracellular retinoid degradation, a two phase culture system using the hydrophobic solvent dodecane was performed for in situ extraction of retinoids from the cells. Under the 2% glycerol as carbon source, we successfully produced high amount retinoids using recombinant E. coli. This work was supported by a grant (2009-0084490) from the Basic Research Program, MEST, a grant from the Next-Generation BioGreen 21 Program (No. 2010-0000), Rural Development Administration, and a BK21 Program of Korea.