Altered redox status in Escherichia coli cells enhances pyruvate production in pH-adjusting culture with a fermenter

Improvements in pyruvate production process were examined using Escherichia coli BW25113?pta/pHfdh strain carrying the formate dehydrogenase gene of Mycobacterium vaccae to change the redox status of the cells. Glucose and formate concentrations, and oxygenation levels determined previously in a shake-flask culture were applied for pyruvate production in a 1 l fermenter. However, pyruvate was not produced under the examined conditions. Detailed pH measurements during the fermenter culture using CaCO₃ revealed that maintaining the pH value around 6.0 plays an important role in stabilizing the pyruvate accumulation. In the pH-adjusting culture around 6.0 with NaOH solution, the concentration and yield of pyruvate were 8.96 g l^?1 and 0.48 g pyruvate g glucose^?1, respectively, which were significantly higher than the values reported in the shake-flask culture (6.79 g l^?1 and 0.32 g pyruvate g glucose^?1).