Concept of cMCSs illustrated with an example of E. coli . A: Solution space formed by the elementary modes of the wild type network of E. coli (36,590 EMs; compare Figure 2). The biomass yield on glucose is plotted against the IPP yield on glucose [C-mol/C-mol] of all computed elementary modes. The deletion task is defined by collecting all modes exhibiting an IPP yield lower than 0.25 C-mol/C-mol in the set of target modes (33,087 EMs). The set of desired modes comprises all EMs having (i) a minimum IPP yield of 0.25 C-mol/C-mol; and (ii) a simultaneous biomass yield strictly higher than zero (268 EMs). B: Example of one specific cMCS. The in silico knockout of transhydrogenase and phosphoglycerate mutase (strategy 2 in Table 3) leads to a reduction of elementary modes. Remaining elementary modes (191) display a minimum IPP yield of 0.28 and a maximum of 0.62 C-mol/C-mol as well as a maximum biomass yield of 0.41 C-mol/C-mol on glucose. In those modes, biomass formation is coupled to a minimum yield of IPP production.