Fig. 2

Construction of hybrid promoter to increase the strength of induction by phenolics. a Identification of a basal promoter inducible by phenolics. The promoter P_emrR is tested in the presence of vanillin by the expression of mCherry in E. coli and is found to be naturally inducible by vanillin that can be inferred by an increase in fluorescence at higher vanillin concentrations. 0 mM vanillin, blue bar; 0.1 mM vanillin, purple bar; 1 mM vanillin, green bar; 5 mM vanillin, orange bar. Each data represent the average of three biological replicates and the error bars represent standard deviation (s.d.); b Hybrid promoter engineering strategy for the construction of higher strength promoters inducible by phenolics. Swapping the spacer region from any stronger promoter with a phenolic-inducible promoter to increase promoter strength but retain inducibility