MODULATION OF METABOLISM OF CLOSTRIDIUM-ACETOBUTYLICUM GROWN IN CHEMOSTAT CULTURE IN A 3-ELECTRODE POTENTIOSTATIC SYSTEM WITH METHYL VIOLOGEN AS ELECTRON CARRIER

The metabolism of Clostridium acetobutylicum was manipulated in chemos tat culture at pH 5 and 6.5 in a three-electrode potentiostatic system with methyl viologen (MV) as the electron carrier. When a constant po tential was applied at pH 5, the broth redox potential continuously de creased and, simultaneously, a high increase in the reduced MV concent ration (MV(+.)) and the specific rate of butanol production was observ ed 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 rat e was not affected. To reach a steady state in glucose limited culture , a control system of the redox potential was required. However, it se ems that C. acetobutylicum is able to adapt its metabolism when the br oth redox potential was regulated at low value. On the other hand, at pH 6.5, the current generated by the electrochemical device had no eff ect either on broth redox potential and MV(+.) concentration or on the metabolism. (C) 1996 John Wiley & Sons, Inc.