Enhancement of 1,3-propanediol production by expression of pyruvate decarboxylase and aldehyde dehydrogenase from Zymomonas mobilis in the acetolactate-synthase-deficient mutant of Klebsiella pneumoniae

The acetolactate synthase (als)-deficient mutant of Klebsiella pneumoniae fails to produce 1,3-propanediol (1,3-PD) or 2,3-butanediol (2,3-BD), and is defective in glycerol metabolism. In an effort to recover production of the industrially valuable 1,3-PD, we introduced the Zymomonas mobilis pyruvate decarboxylase (pdc) and aldehyde dehydrogenase (aldB) genes into the als-deficient mutant to activate the conversion of pyruvate to ethanol. Heterologous expression of pdc and aldB efficiently recovered glycerol metabolism in the 2,3-BD synthesis-defective mutant, enhancing the production of 1,3-PD by preventing the accumulation of pyruvate. Production of 1,3-PD in the pdc- and aldB-expressing als-deficient mutant was further enhanced by increasing the aeration rate. This system uses metabolic engineering to produce 1,3-PD while minimizing the generation of 2,3-BD, offering a breakthrough for the industrial production of 1,3-PD from crude glycerol.