Efficient 3-Hydroxypropionic Acid Production from Glycerol Using Metabolically Engineered Klebsiella Pneumonia

3-Hydroxypropionic acid (3-HP), an important platform compound, has great potential application in producing chemical derivatives, including acrylamide, acrylic acid, 1,3-propanediol, malonic acid, etc. In this study, metabolically engineered Klebsiella pneumonia strains were constructed for efficient 3-HP production from glycerol. The wildtype strain overexpressing aldehyde dehydrogenase (aldH) from E. coli produced reasonable amount of 3-HP (18.3 g/L), however, it still accumulated lot of 1,3-propanediol and lactic acid. Since lactate dehydrogenase (encoding by ldhA) and 1,3-propanediol oxidoreductase (encoding by dhaT) were the key enzymes in the lactic acid and1,3-PDO biosynthesis pathways of K. pneumonia, respectively, the strains with ldhA single deletion (JJQ01) or ldhA and dhaT double deletion (JJQ02) were constructed by using the method of the λ Red recombination system. The aldehyde dehydrogenase from E.coli were also overexpressed in these two strains, respectively. In the fed-batch experiments of 5-L bioreactor, the metabolically engineered K. pneumonia strain JJQ01(pUC18K-aldH) produced 45.8 g/L of 3-HP with a yield of 0.31 mol/mol glycerol. The 3-HP production was further improved when both of ldhA and dhaT were knockout. About 63 g/L of 3-HP was accumulated in JJQ02(pUC18K-aldH), and the yield of 3-HP was increased to 0.58 mol/mol glycerol.