Fig. 3
In vitro pathway prototying of β-carotene and violacein pathways. a Illustration of gene function in β-carotene synthesis pathway. CrtI was chosen as the target gene for integration regulation in β-carotene pathway. CrtI encodes the desaturase that converts the colorless phytoene to the yellow neurosporene first and then to the red lycopene through four desaturation reactions. Since it is a key enzyme in catalyzing the colorless intermediates to colored molecules, the extent of yellow, red, or orange can indicate the transformation efficiency and visibly display diversification of the pathway with various expression of CrtI. b Promoter integration confirmation and LC-MS quantification of carotenoids in β-carotene pathway. VCre-Vlox system was used for CrtI regulation. Seven promoter-integrated strains were quantified. Error bar represents the standard deviation, n = 3. LC-MS, liquid chromatography and mass spectrometry. c Illustration of gene function in violacein synthesis pathway. VioA was chosen as the target gene for integration regulation in violacein pathway. VioA encodes the flavoenzyme L-tryptophan oxidase that catalyses the incorporation of two molecules of substrate L-tryptophan into indole-3-pyruvic acid imine. It catalyzes the initial step in the violacein synthesis and is important for transforming enough tryptophan substrates for following steps towards full synthesis of the pathway. d Promoter integration confirmation and HPLC quantification of violacein. Both VCre-Vlox system and Cre-loxJT15-loxJTZ17 system were used for VioA regulation. Six promoter-integrated strains were quantified. Error bar represents the standard deviation, n = 3. HPLC, high performance liquid chromatography
