Improvements in pyruvate production process were examined using Escherichia coli BW25113Dpta/ 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).