Construction of a novel expression system in Klebsiella pneumoniae and its application for 1,3-propanediol production.

A novel expression system of Klebsiella pneumoniae was developed in order to improve 1,3-propanediol (1,3-PD) production using a K. pneumoniae-Escherichia coli shuttle vector pET28a consisting of the kanamycin-resistance gene promoter Pkan. The recombinant plasmid pETPkan-cat carrying the chloramphenicol acetyltransferase gene cat as selectable marker was constructed to test the availability of the promoter Pkan in K. pneumoniae. The results showed that the chloramphenicol acetyltransferase was apparently expressed in K. pneumoniae, and the recombinant strain had a high-level resistance to chloramphenicol, suggesting that the promoter Pkan was efficient in K. pneumoniae. Then, the expression system was applied to the expression of 1,3-PD oxidoreductase in K. pneumoniae. The enzyme was over-expressed, and the recombinant K. pneumoniae showed a nearly 3.0-fold decrease in peak level of the intermediary metabolite 3-hydroxypropionaldehyde and an increase of 16.5% in yield of 1,3-PD with respect to the wild-type strain. From these results, the first reported expression system has paved the way for improvement of 1,3-PD production and will be available and efficient for other heterologous gene expression in K. pneumoniae.