Metabolic engineering of Escherichia coli for acetaldehyde overproduction using pyruvate decarboxylase from Zymomonas mobilis

For the sustainable production of acetaldehyde, a key raw-material for a large number of chemical products, microbial production is a promising alternative. We have engineered an Escherichia coli strain for acetaldehyde production from glucose by introducing the pyruvate decarboxylase (Pdc) from Zymomonas mobilis and NADH oxidase (Nox) from Lactococcus lactis. Acetaldehyde production was systematically improved by knocking out the competing metabolic pathways. Multiple knockout strains were created and a final acetaldehyde titre of 0.73 g/L was achieved using a quadruple knockout strain E. coli MC4100 Delta adhE Delta ldhA Delta frdC Delta ackA-pta. In addition to acetaldehyde, about 0.37 g/L acetoin was produced by these strains due to the additional carboligase activity exhibited by pyruvate decarboxylase resulting in a total carbon yield of 0.27 g/g glucose.