Enhanced 1,3-propanediol production in recombinant Klebsiella pneumoniae carrying the gene yqhD encoding 1,3-propanediol oxidoreductase isoenzyme

The yqhD gene from Escherichia coli encoding 1,3-propanediol oxidoreductase isoenzyme (PDORI) and the tetracycline resistant gene (tetR) from plasmid pHY300PLK were amplified by PCR. They were inserted into vector pUC18, yielding the recombinant expression vector pUC18-yqhD-tetR. The recombinant vector was then cloned into Klebsiella pneumoniae ME-308. The overexpression of PDORI in K. pneumoniae surprisingly led to higher 1,3-propanediol production. The final 1,3-propanediol concentration of recombinant K. pneumoniae reached 67.6 g/l, which was 125.33% of that of the original strain. The maximum activity of recombinant PDORI converting 3-HPA to 1,3-PD reached 110 IU/mg after induction by IPTG at 31°C during the fermentation, while it was only 11 IU/mg under the same conditions for the wild type strain. The K _m values of the purified PDORI for 1,3-propanediol and NADP were 12.1 mM and 0.15 mM, respectively. Compared with the original strains, the concentration of the toxic intermediate 3-hydroxypropionaldehyde during the fermentation was also reduced by 22.4%. Both the increased production of 1,3-propanediol and the reduction of toxic intermediate confirmed the significant role of 1,3-propanediol oxidoreductase isoenzyme from E. coli in converting 3-hydroxypropionaldehyde to 1,3-propanediol for 1,3-PD production.