AGITATION AND PRESSURE EFFECTS ON ACETONE-BUTANOL FERMENTATION

Batch fermentations [using Clostridium acetobutylicum] were run at varying agitation rates and were either pressurized to 1 bar (15.2 psig) or non-pressurized. Agitation and pressure both affect the level of dissolved H2 in the media, which in turn influences solvent production. In nonpressurized fermentations volumetric productivity of butanol increased as the agitation rate decreased. While agitation had no significant effect on butanol productivity under pressurized conditions, overall butanol productivity was increased over that obtained in the nonpressurized runs. Maximum butyric acid productivity occurred earlier and increased as agitation increased. Peak H2 productivity occurred simultaneously with peak butyric acid productivity. The proportion of reducing equivalents used in forming the above products was determined using a redox balance based on the fermentation stoichiometry. An inverse relationship between the final concentrations of acetone and acetoin was found in all fermentations studied. Agitation and pressure are important parameters for solvent productivity in acetone-butanol fermentation.