Quorum Sensing-Based Dual-Function Switch and Its Application in Solving Two Key Metabolic Engineering Problems

Metabolic engineering aims to achieve high yields of desired products. The most common strategies focus on optimization of metabolic flux distributions. The dynamic activation or inhibition of gene expression through quorum sensing (QS) has been applied to metabolic engineering. In this study, we designed and constructed a series of QS-based bifunctional dynamic switches (QS switches) capable of synchronizing the up-regulation and down-regulation of genes at different times and intervals. The bifunctional QS switches were based on the Esa QS system, because EsaR regulatory proteins can act as transcriptional activator and repressor. The QS switches' effectiveness and feasibility were verified through fluorescence characterization. Finally, the QS switches were applied to the production of 5-aminolevulinic acid (ALA) and poly-beta-hydroxybutyrate (PHB) to solve two key metabolic engineering problems: necessary gene knockout and redirection of metabolic flux. The production of PHB and ALA was increased 6- and 12-fold in Escherichia coli, respectively.