Metabolic engineering of Escherichia coli W3110 for efficient production of homoserine from glucose

Efficient microbial cell factory for the production of homoserine from glucose has been developed by iterative and rational engineering of Escherichia coli W3110. The whole pathway from glucose to homoserine was divided into three groups, namely, glucose transport and glycolysis ('up-stream'), TCA and glyoxylate cycles ('midstream'), and homoserine module (conversion of aspartate to homoserine and its secretion; 'down-stream'), and the carbon flux in each group as well as between the groups were accelerated and balanced. Altogether, ~18 genes were modified for active and consistent production of homoserine during both the actively-growing and non-growing stages of cultivation. Finally, fed-batch, two-stage bioreactor experiments, separating the growth from the production stage, were conducted for 61 h, which gave the high titer of 110.8 g/L, yield of 0.64 g/g glucose and volumetric productivity of 1.82 g/L/h, with an insignificant amount of acetate (<0.5 g/L) as the only noticeable byproduct. The metabolic engineering strategy employed in this study should be applicable for the biosynthesis of other amino acids or chemicals derived from aspartic acid.