Fig. 1

Crocetin biosynthesis pathway construction in S. cerevisiae. a The paradigm of crocetin biosynthetic pathway in S. cerevisiae. The synthetic pathway to crocetin from β-carotene consists of three enzymes: CrtZ, β-carotene hydroxylase; CCD, carotenoid cleavage dioxygenase and ALD, aldehyde dehydrogenase. b, c Schematic representation of the engineering strategies for CrtZ, CCD and ALD expression cassette. CrtZ expression cassette was integrated into the ho locus of the chromosome, while CCD or CCD/ALD was carried by centromeric plasmid pRS416. ho_L, ho locus left homologous arm; ho_R, ho locus right homologous arm. d, e The HPLC profile of the parent strain SyBE_Sc0014CY06 (orange), zeaxanthin producing strain SyBE_Sc0123Cz12 (yellow), crocetin producing strain SyBE_Sc0123C009 (red), and standard (black). The signals for zeaxanthin (I), β-carotene (II) and lycopene (IV) were detected at 450 nm, while crocetin (III) was at 430 nm. The retention time of the unidentified intermediates which were boxed was close to that of lycopene