High‐level production of 3‐hydroxypropionic acid from glycerol as a sole carbon source using metabolically engineered Escherichia coli

Abstract As climate change is an important environmental issue, the conventional petrochemical‐based processes to produce valuable chemicals are being shifted toward eco‐friendly biological‐based processes. In this study, 3‐hydroxypropionic acid (3‐HP), an industrially important three carbon (C3) chemical, was overproduced by metabolically engineered Escherichia coli using glycerol as a sole carbon source. As the first step to construct a glycerol‐dependent 3‐HP biosynthetic pathway, the dhaB1234 and gdrAB genes from Klebsiella pneumoniae encoding glycerol dehydratase and glycerol reactivase, respectively, were introduced into E. coli to convert glycerol into 3‐hydroxypropionaldehyde (3‐HPA). In addition, the ydcW gene from K. pneumoniae encoding γ‐aminobutyraldehyde dehydrogenase, among five aldehyde dehydrogenases examined, was selected to further convert 3‐HPA to 3‐HP. Increasing the expression level of the ydcW gene enhanced 3‐HP production titer and reduced 1,3‐propanediol production. To enhance 3‐HP production, fed‐batch fermentation conditions were optimized by controlling dissolved oxygen (DO) level and employing different feeding strategies including intermittent feeding, pH‐stat feeding, and continuous feeding strategies. Fed‐batch culture of the final engineered E. coli strain with DO control and continuous feeding strategy produced 76.2 g/L of 3‐HP with the yield and productivity of 0.457 g/g glycerol and 1.89 g·L −1 ·h −1 , respectively. To the best of our knowledge, this is the highest 3‐HP productivity achieved by any microorganism reported to date.