Figure 9. The solution space of metabolic networks. In the three-dimensional unconstrained flux space of a hypothetical network, fluxes can assume any value.
a) Solutions obtained by restrictions stoichiometry, enzymatic limitations or the balance of mass, then the feasible solution space is reduced to a cone;
b) Restrictions by using an objective function, such as maximizing biomass accumulation, can identify a coordinate (set of flux values) on an of the feasible flux cone (red point). (adapted from Lanzeni et al. 2008).