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.