Fig. 2

Development of colour-based phenotypic screen for HBA production. Pathway design of the HBA module with a secondary marker (kanamycin resistance) and promoter library assembly. Yellow-orange colonies that were used for selection of active pathway variants were identified after ~ 3 days of growth at 30 °C on 2YT agar supplemented with 50 mM Tris–HCl pH 8 buffer, followed by liquid growth (from triplicate single colonies) and quantification of pathway intermediates by LC–MS. Sequencing summary is provided in Additional file 1: Table S2. Data and error bars (standard deviation) is representative of three biological repeats