Identification and characterization of the propanediol utilization protein PduP of Lactobacillus reuteri for 3-hydroxypropionic acid production from glycerol
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Although the de novo biosynthetic mechanism of 3-hydroxypropionic acid (3-HP) in glycerol-fermenting microorganisms is still unclear, the propanediol utilization protein (PduP) of Lactobacillus species has been suggested to be a key enzyme in this regard. To verify this hypothesis, a pduP gene from Lactobacillus reuteri was cloned and expressed, and the encoded protein was characterized. Recombinant L. reuteri PduP exhibited broad substrate specificity including 3-hydroxypropionaldehyde and utilized both NAD+ and NADP+ as a cofactor. Among various aldehyde substrates tested, the specific activity was highest for propionaldehyde, at pH 7.8 and 37 °C. The K m and V max values for propionaldehyde in the presence of NAD+ were 1.18 mM and 0.35 U mg−1, respectively. When L. reuteri pduP was overexpressed in Klebsiella pneumoniae, 3-HP production remarkably increased as compared to the wild-type strain (from 0.18 g L−1 to 0.72 g L−1) under shake-flask culture conditions, and the highest titer (1.38 g L−1 3-HP) was produced by the recombinant strain under batch fermentation conditions in a bioreactor. This is the first report stating the enzymatic properties of PduP protein and the probable role in biosynthesis of 3-HP in glycerol fermentation.
KeywordsGlycerol 3-Hydroxypropionic acid Klebsiella pneumoniae Lactobacillus reuteri Propanediol utilization protein PduP
The authors are very thankful to Prof. Sunghoon Park for generously supplying 3-hydroxypropionaldehyde. This work was supported by the Korea Research Foundation (KRF) grant funded by Korea Government (MEST) (Basic Researcher Promotion Program 2010-0015871).
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