Figure 7.

Flux-sum intensification of competitive and uncompetitive metabolites. In the base case, the maximum biomass production can be achieved due to optimal distribution of carbon fluxes to all the biomass components. If we intensify the flux-sum of any of the competitive metabolites (red nodes), the metabolite would compete for the limited resources and perturb the optimal distribution of carbon fluxes, resulting in reduced biomass production. On the other hand, intensifying the flux-sums of uncompetitive metabolites (blue nodes) does not perturb the optimal carbon flux distribution while the flux-sum of fully utilized metabolites (orange nodes) cannot be intensified. It is obvious that all metabolites contributing to biomass production shown in the figure are both essential and competitive.