Designing Autonomous Biological Switches to Rewire Carbon Flux for Chemical Production in <i>Escherichia coli</i>

Microbial cell factories provide an environmentally friendly and sustainable platform capable of utilizing inexpensive substrates to produce chemicals. However, modifying the strain through metabolic engineering to enhance the synthesis of the target product often disrupts the rational allocation of metabolic flux, leading to suboptimal production efficiency in the strain. In this study, to achieve rational allocation of metabolic flux, we designed two autonomous dynamic regulatory systems with good universality and portability: a single-function regulatory switch (SFRS) and a dual-function regulatory switch (DFRS), by integrating quorum sensing (QS) systems and stationary phase promoters. As a proof of concept, the SFRS was used to reallocate the metabolic flux distribution, dividing the strain production process into precursor accumulation and product synthesis phases to reduce the toxicity of premature cadaverine accumulation on cells. This increased the cadaverine titer to 62.5 g/L with a productivity of 1.7 g/L/h in a 5 L fermenter. Additionally, the DFRS was implemented to balance the metabolic flux between cell growth and product synthesis, decoupling cell growth from succinate synthesis. This increased the succinate titer to 128.2 g/L with a productivity of 1.8 g/L/h in a 5 L fermenter. These results emphasize the potential of SFRS and DFRS as powerful metabolic flux regulation tools to enhance the production of valuable chemicals.