title: Insights into 3-hydroxypropionic acid biosynthesis revealed by overexpressing native glycerol dehydrogenase inKlebsiella pneumoniae.
abstract: InKlebsiella pneumoniae, glycerol dissimilation involves parallel oxidation and reduction pathways. Oxidation pathway provides adenosine triphosphate (ATP) and cofactors to sustain cell growth, while reduction pathway presents 3-hydroxypropionic acid (3-HP) and 1,3-propanediol(1,3-PDO), which are commercially attractive platform chemicals. Previous metabolic engineering ofK.pneumoniaefocused on the intensification of reduction pathway; however, it failed to overproduce 3-HP or 1,3-PDO. Contrary to this strategy, here we show that overexpression of glycerol dehydrogenase (dhaD), the first functional enzyme in oxidation pathway, can efficiently stimulate cell growth and facilitate 3-HP accumulation. Under microaerobic conditions, although metabolic burden arising from plasmid replication, the recombinantK. pneumoniaeoverexpressingdhaDgrew actively and showed 60% enhancement of 3-HP compared to the control. In particular, overexpression of dhaD increased the activity of glycerol dehydratase, indicating the concerted action of two enzymes and the interdependence between glycerol oxidation and reduction pathways. Moreover, the strain overexpressing dhaD produced more lactic acid yet less acetic acid than the control, implying the interplay between dhaD expression and the formation of byproducts. Together, not only showing that intensifying glycerol oxidation pathway is beneficial to 3-HP production, this study also reveals the structural rigidity ofdhaoperon that mediates glycerol dissimilation inK.pneumoniae.
authors.affiliation: College of Life Science and Technology, Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology , Beijing , P. R. China.
authors.forename: Ming-Yue
authors.initials: MY
authors.lastname: Su
authors.affiliation: College of Life Science and Technology, Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology , Beijing , P. R. China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Biochemical Engineering, Beijing Union University , Beijing , P. R. China.
authors.forename: Xi-Zhen
authors.initials: XZ
authors.lastname: Ge
authors.affiliation: College of Life Science and Technology, Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology , Beijing , P. R. China.
authors.forename: Ping-Fang
authors.initials: PF
authors.lastname: Tian
keywords: 3-Hydroxypropionic acid; Klebsiella pneumoniae; glycerol dehydrogenase; overexpression