Vanillin production envelope of the augmented E. coli metabolic network for a basic 10 mmol/gDW per hour uptake rate of glucose. Points A, B, and C denote the maximum growth points associated with the one, two, and four reaction deletion mutant networks, respectively. Note that the level “augmented” refers to the E. coli wild-type network augmented with the three non-native reactions. An anaerobic mode of growth is suggested in all cases.