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.