Fermentation redox potential control on the 1,3-propanediol production by Lactobacillus panis PM1

The fermentation redox potential was controlled during the production of 1,3-propanediol (PDO) by Lactobacillus panis PM1. Results show that the best redox potential level was at −200 mV at which had the highest PDO production (23.38 g/L) when compared to that controlled at -250 mV, −150 mV, and without control. For the redox potential level under investigation, the mass PDO yield with respect to glycerol was between 0.66 and 0.82. Potassium ferricyanide was chosen as an oxidant to control the redox potential level. With the addition of oxidant, the batch fermentation time was noticeably reduced compared to the one without the addition of oxidant. Furthermore, co-substrate utilization of glucose and glycerol was observed when potassium ferricyanide was present. It was postulated that such a co-substrate utilization pattern resulted from the redox imbalance where the activities of acetaldehyde dehydrogenase and alcohol dehydrogenase were retarded by the presence of potassium ferricyanide. To overcome the redox imbalance, the glycerol-reductive pathway was triggered to serve as the electron source to fuel the glycolysis pathway and PDO formation. The developed redox potential control strategy may benefit other specifically isolated PDO-producing strains and industrial PDO green processing to further enhance their productivity.