Validation of ttg operon system-based E. coli biosensor for quantitative monitoring of resveratrol biosynthesis

Transcription factor (TF)-based whole-cell biosensors provide genetically encoded tools for detecting intracellular metabolites and have potential applications in monitoring microbial biosynthetic processes. TtgR, a multidrug-responsive transcriptional repressor from Pseudomonas putida , responds to several flavonoids, including resveratrol, and has previously been developed as a whole-cell biosensor for quantitative detection of flavonoids using authentic standards. In this study, we extended the application of the TtgR-based biosensor to the quantitative monitoring of resveratrol produced through a heterologous biosynthetic pathway in engineered Escherichia coli . Resveratrol production was monitored over time using the TtgR-based biosensor, and the estimated concentrations were compared with those determined by HPLC. The biosensor-derived concentrations showed relative agreement of 92.7–93.8% with the corresponding HPLC measurements, supporting the quantitative applicability of the biosensor for monitoring metabolite production in a microbial production system. In addition, ligand-response profiles of TtgR WT and selected engineered variants were independently evaluated in this study using resveratrol, quercetin, and naringenin. The engineered variants exhibited distinct ligand-response profiles, suggesting the potential extension of the TtgR-based sensing platform to other flavonoid production pathways. These results demonstrate the application of a previously established TtgR-based sensing platform beyond analytical characterization with authentic standards toward quantitative monitoring of biosynthetically produced metabolites in engineered microbial systems.