Metabolic Switch

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A method for biosynthesis of carbon-based products of interest in an engineered host cell, comprising:

• a. culturing an engineered host cell, wherein said engineered host cell is auxotrophic for at least one exogenous compound, and wherein said engineered host cell comprises at least one control element, at least one heterologous metabolic pathway, at least one second metabolic pathway, and a shared metabolic junction, wherein said exogenous compound controls the activity of a control element and said control element controls carbon flux through said metabolic junction to said heterologous metabolic pathway or to said second metabolic pathway, and wherein said culturing is in the presence of said exogenous compound;
• and
• b. depleting said exogenous compound from the culture.

A host cell comprising a control element and a heterologous metabolic pathway, wherein said host cell is auxotrophic for an exogenous compound, wherein said exogenous compound controls activity of said control element, and wherein said control element controls carbon flux through a metabolic junction shared by said heterologous metabolic pathway and at least one second metabolic pathway.