Fig. 5

Metabolic engineering modification of the l-cysteine synthetic module. A A schematic representation of the enhancement of the l-cysteine synthetic module. B l-methionine and l-isoleucine production and OD₆₀₀ of MET13, MET14, MET15, MET16, and MET17. C Relative transcript levels of related genes of MET15 in shake flask cultivation. D Effect of overexpression of key genes in the sulfur assimilation pathway on l-methionine production. 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)