Improvement of 1,3-Propanediol Production with a Recombinant Strain Klebsiella pneumoniae F-1 by Regulating Redox Potential

Redox potential (also called oxidoreduction potential, ORP) is one of important indicators to monitor the anaerobic fermentation of Klebsiella pneumoniae. In this report, the preferred ORP of a recombinant strain K. pneumoniae F-1 was investigated by controlling the ORP of broth into four levels of-190,-210,-240 and-290 mV. The results showed that in the fermentation of ORP at-240 mV, the highest final 1,3-propanediol concentration and molar yield of were achieved, being 81.5 g/L and 0.423 mol/mol, respectively. This preferred ORP to the genetic modified strain was different from those of both the wild strain K. pneumoniae M5aL (-190 mV) and the mutant K. pneumoniae M5aL YMU2 (-280 mV). It is demonstrated that the modification of the metabolic pathway in the K. pneumoniae F-1 exerted effects on the preferred ORP of the strain. The effect of ORP on re-distribution of the metabolites was also investigated. The results demonstrated that the reduction environment facilitated the pathways from glycerol to reduction end-metabolites, such as 1,3-propanediol, ethanol and 2,3-butanediol. This work is the first investigation on the ORP regulation method in a recombinant strain, which will provide insight into the mechanism of ORP regulation in anaerobic fermentations.