Table 1.

Comparison of precision metabolic engineering, dynamic metabolic engineering, and general metabolic engineering approaches

Characteristic	General Metabolic Engineering	Dynamic Metabolic Engineering	Precision Metabolic Engineering
Engineering optimization goal	Product titer, yield, productivity	Product titer, yield, productivity	State-based selectivity and response sensitivity
Temporal behavior	None; optimization through static manipulations	System behavior necessarily changes over time	System behavior may (but does not necessarily) change over time
Number of possible states	One; static optimization produces singular desired state	Two; change between states initiated at time point during production	Many; states could change over time or be determined by initial concentration of sensory molecule
Signal that dictates metabolic state	None; state of system predetermined	Exogenous molecules, naturally produced metabolites	Exogenous molecules, naturally produced metabolites
Methods used to change metabolic state	None; state of system predetermined	Inducible transcriptional, post-transcriptional regulation	Inducible transcriptional, post-transcriptional regulation
Necessary degree of control between multiple desired metabolic states	None; state of system predetermined	Majority of metabolic flux must be through desired pathways, but leakiness in transcription and enzymatic activity may be permitted	All measurable metabolic flux must be through desired pathways, leakiness in transcription and enzymatic activity not permitted
Examples	Industrial production of biofuels, pharmaceuticals, commodity chemicals	Industrial production in which titer and productivity can be increased either by shifting from a growth phase to a production phase or by balancing fluxes to reduce toxic intermediates	Metabolite biosensors, portable pharmaceutical production, targeted drug delivery