(264e) Establishing an Acetate-Responsive Biosensor System for Relieving Overflow Effect and Enhancing Microbial Production

Escherichia coli accumulates acetate as a metabolic by-product upon rapid glucose uptake, even in aerobic environments. This kind of phenomenon, known as overflow metabolism, has also been found in various cell types, such as yeast cells and mammalian cells. In the past few decades, researchers have devoted significant efforts to investigate the underlying mechanisms, and substantial data and models suggested that overflow metabolism subject to the inherent regulation networks for carbon flux allocation and redox balance. Nevertheless, acetate is regarded as a detrimental by-product in most microbial production scenarios, as the accumulated acetate is proved to impair cell growth and the expression of heterologous proteins. Furthermore, diverting carbon flow to acetate production leads to substrate waste and limits the yield. Despite numerous metabolic engineering strategies have been proposed to alleviate overflow metabolism, acetate accumulation remains a challenging issue due to its intricate correlations with central metabolic pathways. To fundamentally address this issue, we regarded acetate as a metabolic indicator and characterized an acetate-responsive biosensor system to monitor the cellular metabolic status. By applying the biosensor system on regulating the expression of redox-related targets, we released the metabolic stress caused by unbalanced redox ratio, reducing the waste of carbon flux on overflow pathway and redirecting more carbon flux towards the desired product. Finally, we demonstrated the outstanding performance of the dynamic regulation system by achieving the enhanced phloroglucinol production. Overall, this study explored the application of overflow-responsive biosensors on cellular metabolism self-regulation, providing a general approach for engineering cell status to improve microbial production.