PRODUCTION OF ACETONE-BUTANOL-ETHANOL BY CLOSTRIDIUM-ACETOBUTYLICUM USING A SPIN FILTER PERFUSION BIOREACTOR

The performance of a custom-built cell perfusion bioreactor was invest igated in the biosynthesis of acetone, butanol and ethanol by Clostrid ium acetobutylicum. In a continuous flow operating mode with total cel l retention, i.e., when only the cell-free spent medium was removed, s teady-state concentrations of acetone, butanol, ethanol, butyric acid, acetic acid and residual glucose and increasing biomass concentration were observed up to 49 g l(-1) of glucose in the feed stream. The ste ady-state concentrations of acetone, butanol, ethanol, butyric acid an d acetic acid were independent of the dilution rate and a function of the feed glucose concentration. Under these conditions a complete util ization of glucose with a maximum volumetric productivity of 1.14 g l( -1) h(-1) of total solvents was obtained. Increasing the feed glucose concentration to 58 and 63 g l(-1) in total cell retention mode led to sustained undampened oscillations resulting from product inhibition. These oscillations were eliminated when a full harvest stream of cell containing spent medium was withdrawn in addition to the cell-free fil trate stream.