Rank of the output. The output of the UP Finder is the abbreviated reaction names of the selected key pathways in Step (2). A termed parameter, Ratio, which is the ratio of each fluxopt over their associated wild-type fluxes (fluxwt) was used for ranking the output from high to low. Because Ratio reflects the up-regulated level for each reaction, the one with the highest Ratio value suggests the highest preference when considering gene overexpression in engineering of the targeted overproduction.