Selective retinol production by modulating the composition of retinoids from metabolically engineered E. coli

Retinoids can be produced from E. coli when introduced with the β-carotene biosynthesis pathway and the BCMO gene. E. coli has no inherent metabolic pathways related to retinoids, therefore only retinal should be produced from the cleavage of β-carotene by BCMO. However, retinol and retinyl acetate were also produced in significant amounts, by the non-specific activity of inherent promiscuous enzymes or the antibiotic resistance marker of the retinal-producing plasmids. Retinol was produced by the ybbO gene of E. coli which encodes oxidoreductase and retinyl acetate was produced by the chloramphenicol resistance gene, called cat gene which encodes chloramphenicol acetyltransferase, present within the pS-NA plasmid that also contains the mevalonate pathway. The composition of retinoids could be modulated by manipulating the relevant genes. The composition of retinol, a commercially important retinoid, was significantly increased by the overexpression of ybbO gene and the removal of cat gene in the recombinant E. coli, which suggests the possibility of selective retinoid production in the future.