The parameter fluxwt represents wild-type flux that is the flux solution of the wild-type model, and fluxopt represents the optimum flux that is the flux solution of the theoretical maximum yield model. The up-regulation ratio (Ratio) is defined as the ratio of fluxopt to fluxwt of a reaction (Ratio = fluxopt / fluxwt). And the Yield is simulated product yield of the targeted product by using fluxopt of a reaction as the constraint, in which maximizing cell growth is the objective function.