Improving lycopene production in Escherichia coli by engineering metaboliccontrol

Metabolic engineering has achieved encouraging success in producing foreign metabolites in a variety of hosts. However, common strategies for engineer ing metabolic pathways focus on amplifying the desired enzymes and deregula ting cellular controls. As a result, uncontrolled or deregulated metabolic pathways lead to metabolic imbalance and suboptimal productivity. Here we h ave demonstrated the second stage of metabolic engineering effort by design ing and engineering a regulatory circuit to control gene expression in resp onse to intracellular metabolic states. Specifically, we recruited and alte red one of the global regulatory systems in Escherichia coli, the Ntr regul on, to control the engineered lycopene biosynthesis pathway. The artificial ly engineered regulon, stimulated by excess glycolytic flux through sensing of an intracellular metabolite, acetyl phosphate, controls the expression of two key enzymes in lycopene synthesis in response to flux dynamics. This intracellular control loop significantly enhanced lycopene production whil e reducing the negative impact caused by metabolic imbalance. Although we d emonstrated this strategy for metabolite production, it can be extended int o other fields where gene expression must be closely controlled by intracel lular physiology, such as gene therapy.