Genetically engineered biosynthetic pathways for nonnatural C(60) carotenoids using C(5)-elongases and C(50)-cyclases in Escherichia coli

While the majority of the natural carotenoid pigments are based on 40-carbon (C(40)) skeleton, some carotenoids from bacteria have larger C(50) skeleton, biosynthesized by attaching two isoprene units (C(5)) to both sides of the C(40) carotenoid pigment lycopene. Subsequent cyclization reactions result in the production of C(50) carotenoids with diverse and unique skeletal structures. To produce even larger nonnatural novel carotenoids with C(50) + C(5) + C(5) = C(60) skeletons, we systematically coexpressed natural C(50) carotenoid biosynthetic enzymes (lycopene C(5)-elongases and C(50)-cyclases) from various bacterial sources together with the laboratory-engineered nonnatural C(50)-lycopene pathway in Escherichia coli. Among the tested enzymes, the elongases and cyclases from Micrococcus luteus exhibited significant activity toward C(50)-lycopene, and yielded the novel carotenoids C(60)-flavuxanthin and C(60)-sarcinaxanthin. Moreover, coexpression of M. luteus elongase with Corynebacterium cyclase resulted in the production of C(60)-sarcinaxanthin, C(60)-sarprenoxanthin, and C(60)-decaprenoxanthin.