The working procedure of the UP Finder. Mutant model, the overproducing metabolic network, the model with flux distribution under the theoretical maximum yield conditions (flux distribution for reaching theoretical maximum yield of a metabolite); fluxwt, wild-type flux, which is the flux distribution of the wild-type conditions; fluxopt, optimum flux, which is the flux distribution of the theoretical maximum yield conditions; Ratio, up-regulation ratio, which is the ratio of the optimum flux to the wild-type flux of a reaction; Yield, simulated yield of the targeted product by using the optimum flux of a reaction as the constraint.