Designing\nAutonomous Biological Switches to Rewire\nCarbon Flux for Chemical Production in Escherichia\ncoli

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