Fig. 1
From: A mixed-integer linear programming approach to the reduction of genome-scale metabolic networks
Solid arcs correspond to active reactions, dotted arcs to inactive reactions. In a, the flux vector satisfies the functionality of carrying flux through the biomass reaction while having oxygen uptake. In b, the functionality is carrying flux through the biomass reaction while there is no oxygen uptake. Combining the two flux vectors leads to the network in c, which contains 7 active reactions. A minimum subnetwork enabling both functionalities with only 6 reactions is given in (d). The corresponding binary variables for 1d would have the following values: a 1=1,a 2=1,a 3=1,a 4=1,a 5=1,a 6=0,a 7=0,a 8=1, where a i corresponds to reaction r i