Fig. 2. Biosensor performance. eGFP gene expression data in the absence (empty shapes) and presence of the ferC repressor (filled shapes), for the P_ferB (triangles), P_PC (circles), and P_LC (diamonds) biosensors in E. coli BL21. The fluorescent gene expression normalised to cell density (RFU/OD₆₀₀) was expressed relative to the P_LC biosensor, and the dose response curves were fitted to increasing concentrations of ferulic acid.