Improvement of 3-hydroxypropionic acid tolerance in Klebsiella pneumoniae by novel transporter YohJK.

3-Hydroxypropionic acid (3-HP) is a platform chemical which has potential applications in cosmetic and polymer industries. Microbial production of 3-HP is hampered by its toxic effect when its concentration is high (>300 mM). In this study, the effect of yohJK overexpression (via yieP deletion or episomal overexpression) on 3-HP tolerance was investigated in Klebsiella pneumoniae, Pseudomonas denitrificans and P. asiatica. The deletion of yieP homolog could improve 3-HP tolerance in K. pneumoniae. Transcriptional analysis suggested that, among the two yohJK homologs of K. pneumoniae, expression of yohJK1, not yohJK2, was under the negative control of YieP. Furthermore, deletion of yieP significantly reduced cytoplasmic 3-HP concentration when determined by 3-HP biosensor and enhanced 3-HP tolerance and 3-HP production. This study demonstrates that the YohJK1 functions as 3-HP transporter in K. pneumoniae and their overexpression by the yieP deletion is a good strategy to enhance 3-HP tolerance and its production.