HOW NEUTRAL RED MODIFIED CARBON AND ELECTRON FLOW IN CLOSTRIDIUM-ACETOBUTYLICUM GROWN IN CHEMOSTAT CULTURE AT NEUTRAL PH

The metabolism of Clostridium acetobutylicum was manipulated, at neutr al pH and in chemostat culture, by the addition of Neutral red, a mole cule that can replace ferredoxin in the oxide-reduction reactions cata lysed by the enzymes involved in the distribution of the electron flow . Cultures grown on glucose alone produced mainly acids while cultures grown on glucose plus Neutral red produced mainly alcohols and butyra te and low levels of hydrogen. We demonstrated that just after additio n of Neutral red to an acidogenic culture, the simultaneous utilizatio ns of ferredoxin and dye deviate electron flow from hydrogen to NADH p roduction initially by the enzymatic regulation of in vivo hydrogenase and ferredoxin NAD reductase activities. The higher NAD(P)H pool gene rated might, thereafter, be the signal for the setting up of a new met abolism. In the resulting steady-state, the NAD(P)H ''pressure'' is ma intained by high ferredoxin NAD and NADP reductases lever associated t o a low NADH ferredoxin reductase level. The regeneration of NAD is ma inly achieved via the induced or increased NADH-dependent aldehyde and alcohol dehydrogenase activities.