Dynamic Regulation of Efflux Pump Protein AcrA by Quorum Sensing System to Improve Free Fatty Acids Production in Escherichia coli

ABSTRACT Microbial production of free fatty acids (FFAs) is an eco‐friendly and promising approach. However, FFAs accumulation within microbial cells imposes stress and toxicity, impairing biosynthetic performance. These challenges can be alleviated by exporting FFAs through the efflux system AcrAB‐TolC in Escherichia coli , but the expression of these membrane channels needs to be fine‐tuned. In this study, we employed a quorum sensing (QS) system to dynamically regulate the expression of AcrAB‐TolC, thereby enhancing FFAs efflux and production. Two regulatory patterns of gene expression were designed to respond to increasing cell density: EsaI/R‐P esaS drives an initial increase followed by a decrease pattern, and EsaI/R‐P esaR enables a slow linear increase pattern. The L19IR‐P R ‐ acrA strain, in which acrA expression is auto‐induced by P esaR , exhibited a 142% increase in extracellular FFAs and an 11% increase in total FFAs titer compared to the L19IR strain, which lacks acrA regulation. Auto‐induced dynamic regulation of acrA demonstrates significant improvements in both FFAs efflux and overall production, while maintaining cell growth and membrane stability. Our results highlight the potential of QS‐mediated dynamic regulation of efflux pumps to enhance the synthesis of bioproducts toxic to microorganisms.