INVESTIGATION OF ACETONE-BUTANOL-ETHANOL FERMENTATION BY FLUORESCENCE

Acetone-butanol-ethanol fermentation by Clostridium acetobutylicum was followed by two variations of fluorescence: the intrinsic fluorescence of NADH, related to bacterial metabolism, and the fluorescence polarization of extrinsic 1,6-diphenyl-1,3,5-hexatriene (DPH) related to membrane fluidity. First, NADH fluorescence was correlated to the specific rate production of butyric acid (linear relationship) and to enzymatic activities (acetate kinase, butyrate kinase and aceto-acetate decarboxylase). Second, a simultaneous increase in both DPH anisotropy (order parameter increase) and butanol production was observed. Even though these results seem contradictory, because of the well-known fluidizing effect of butanol on lipids, the apparent changes in fluidity can be the result of adaptive membrane alteration.