Modulation of metabolism of Clostridium acetobutylicum grown in chemostat culture in a three-electrode potentiostatic system with methyl viologen as electron carrier.

The metabolism of Clostridium acetobutylicum was manipulated in chemostat culture at pH 5 and 6.5 in a three-electrode potentiostatic system with methyl viologen (MV) as the electron carrier. When a constant potential was applied at pH 5, the broth redox potential continuously decreased and, simultaneously, a high increase in the reduced MV concentration (MV(+.)) and the specific rate of butanol production was observed while butyric acid was taken up. A linear relationship was reported between the specific rate of NAD(P)(+) reduction by ferredoxin-NAD(P)(+) reductase and the broth redox potential, as long as the growth rate was not affected. To reach a steady state in glucose limited culture, a control system of the redox potential was required. However, it seems that C. acetobutylicum is able to adapt its metabolism when the broth redox potential was regulated at low value. On the other hand, at pH 6.5, the current generated by the electrochemical device had no effect either on broth redox potential and MV(+.) concentration or on the metabolism.