Engineering microaerobic metabolism of E. coli for 1,2-propanediol production.

Establishment of novel metabolic pathways for biosynthesis of chemicals, fuels and pharmaceuticals has been demonstrated in Escherichia coli due to its ease of genetic manipulation and adaptability to varying oxygen levels. E. coli growing under microaerobic condition is known to exhibit features of both aerobic and anaerobic metabolism. In this work, we attempt to engineer this metabolism for production of 1,2-propanediol. We first redirect the carbon flux by disrupting carbon-competing pathways to increase the production of 1,2-propanediol microaerobically from 0.25 to 0.85 g/L. We then disrupt the first committed step of E. coli's ubiquinone biosynthesis pathway (ubiC) to prevent the oxidation of NADH in microaerobic conditions. Coupling this strategy with carbon flux redirection leads to enhanced production of 1,2-propanediol at 1.2 g/L. This work demonstrates the production of non-native reduced chemicals in E. coli by engineering its microaerobic metabolism.