Fig. 4

In silico simulation of the metabolic flux distribution in the wild-type strain and l-methionine overproducer by flux balance analysis. A The metabolic flux distribution in the WT strain (blue) and l-methionine overproducer (red). B The impacts of increased CysE reaction flux on intracellular metabolic flux by FBA using l-methionine synthase as the objective function with 20% theoretical maximum biomass constraint. The CysE reaction flux was set to 1.0-, 3.0-, 5.0-, 10.0-, and 20.0-fold (from left to right) compared to that in the WT strain. C Strains WTΔilvA and MET13ΔilvA on solid M9 medium with or without 0.5 g/L l-isoleucine supply. D Growth of WT, WTΔilvA, MET13, and MET13ΔilvA in M9 medium with or without 0.5 g/L l-isoleucine supply. E Growth of MET13 and MET13ΔmetB in fermentation medium with or without 0.5 g/L l-methionine supply. F l-methionine and l-isoleucine production and OD₆₀₀ of MET13 and MET13 with l-cysteine supply. Data are presented as the mean values with the standard deviation from three biological replicates. One-way analysis of variance (ANOVA) was used to determine significant differences (* p < 0.05, ** p < 0.01)