Inactivation of hydrogenase-3 leads to enhancement of 1,3-propanediol and 2,3-butanediol production by Klebsiella pneumoniae.

Klebsiella pneumoniae can use glucose or glycerol as carbon sources to produce 1,3-propanediol or 2,3-butanediol, respectively. In the metabolism of Klebsiella pneumoniae , hydrogenase-3 is responsible for H 2 production from formic acid, but it is not directly related to the synthesis pathways for 1,3-propanediol and 2,3-butanediol. In the first part of this research, hycEFG , which encodes subunits of the enzyme hydrogenase-3, was knocked out, so K. pneumoniae Δ hycEFG lost the ability to produce H 2 during cultivation using glycerol as a carbon source. As a consequence, the concentration of 1,3-propanediol increased and the substrate (glycerol) conversion ratio reached 0.587 mol/mol. Then, K. pneumoniae Δ ldhA Δ hycEFG was constructed to erase lactic acid synthesis which led to the further increase of 1,3-propanediol concentration. A substrate (glycerol) conversion ratio of 0.628 mol/mol in batch conditions was achieved, which was higher compared to the wild type strain (0.545 mol/mol). Furthermore, since adhE encodes an alcohol dehydrogenase that catalyzes ethanol production from acetaldehyde, K. pneumoniae Δ ldhA Δ adhE Δ hycEFG was constructed to prevent ethanol production. Contrary to expectations, this did not lead to a further increase, but to a decrease in 1,3-propanediol production. In the second part of this research, glucose was used as the carbon source to produce 2,3-butanediol. Knocking out hycEFG had distinct positive effect on 2,3-butanediol production. Especially in K. pneumoniae ΔldhAΔadhEΔhycEFG , a substrate (glucose) conversion ratio of 0.730 mol/mol was reached, which is higher compared to wild type strain (0.504 mol/mol). This work suggests that the inactivation of hydrogenase-3 may have a global effect on the metabolic regulation of K. pneumoniae , leading to the improvement of the production of two industrially important bulk chemicals, 1,3-propanediol and 2,3-butanediol. • Hydrogenase-3 responsible for H 2 generation in Klebsiella pneumoniae. • Knockout of hycEFG promotes 1,3-propanediol and 2,3-butanediol production. • The conversion ratio of 1,3-propanediol was 0.628 mol/mol for Kp Δ ldhA Δ hycEFG. • The conversion ratio of 2,3-butanediol was 0.730 mol/mol for Kp Δ ldhA Δ adhE Δ hycEFG. [ABSTRACT FROM AUTHOR]