Figure 5.

Optimize β-carotene production using a combinatorial assembly method. (A) The activity of three promoters CYC1, TEF2 and TDH3 was measured in our reporter system. The three promoters were chosen to represent the weak (blue), medium (green) and strong (red) promoter, respectively. (B) The production of β-carotene using different combination of the three promoters. The promoters were listed at the left most and color-coded as that in (A). Two colonies were spotted and the amount of β-carotene in each clone was quantified. (C) A total of 151 promoters were used to drive expression of each gene to optimize the production of β-carotene. Fifty clones, which contain the complete pathway, were randomly isolated. The identity of the promoter in front of each gene was determined and color-coded based on their activities for each isolates. The corresponding β-carotene content was quantified. The cells colored in grey indicate the identity of the promoter has not been determined. The colonies from (B) and (C) were grown on SC-Leu plates for 48 h with the starting optical density (OD₆₀₀) being 1.