Transcriptional Regulation of Genes Involved in 3-Hydroxypropionic Acid Production in Response to Aeration of Recombinant Klebsiella pneumoniae.

Abstract

We have described a metabolically engineered strain of Klebsiella pneumoniae/pUC18kan-aldHec that could convert glycerol to 3-hydroxypropionic acid (3-HP) effectively. In this study, the transcription of the genes encoding aldehyde dehydrogenase (AldH) and glycerol dehydratase (DhaB) responsible to 3-HP-biosynthesis, key enzymes in PP pathway and TCA cycle, as well as hydrogenases was observed under anaerobic, microaerobic, and aerobic conditions using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). During the fast growth and slow growth phases of cell growth, the aldH transcription levels were 7.0- and 2.1-fold enhanced under microaerobic condition, and 12.4- and 0.14-fold under fully aerobic condition, compared to the anaerobic control, while transcription of dhaB showed a downregulated manner due to aeration. Moreover, aeration increased the transcription levels of zwf, sucA, and sdhAB during the fast growth phase of the cell growth. The results also indicated that the hydrogenase 3 (hycBCDFG) and formate dehydrogenase (fdhA) mediated formate hydrogen lyase pathway was the main route to produce hydrogen and consume the excess NADH. These characteristics are useful for understanding and improving 3-HP biosynthesis in K. pneumoniae.