Engineering of Escherichia coli for Krebs cycle-dependent production of malic acid

Background Malate is a C4-dicarboxylic acid widely used as an acidulant in the food and beverage industry. Rational engineering has been performed in the past for the development of microbial strains capable of efficient production of this metabolite. However, as malate can be a precursor for specialty chemicals, such as 2,4-dihydroxybutyric acid, that require additional cofactors NADP(H) and ATP, we set out to reengineer Escherichia coli for Krebs cycle-dependent production of malic acid that can satisfy these requirements.