CONTINUOUS PRODUCTION OF ACETATE BY CLOSTRIDIUM-THERMOACETICUM IN A CELL-RECYCLE MEMBRANE BIOREACTOR

A mutant strain of Clostridium thermoaceticum was studied in a cell-re cycle membrane bioreactor for production of acetate from glucose. With 20-30 g l(-1) glucose in the feed and a cell concentration of 5 g l(- 1), dilution rates up to 0.25 h(-1) resulted in complete utilization o f substrate, resulting in a productivity of 4 g l(-1)h(-1) and acetate concentration of 16 g l(-1) in the broth. This productivity was 10-fo ld higher than that of the batch fermenter. Higher cell concentrations allowed higher glucose concentrations to be used, resulting in acetat e concentrations of 44 g l(-1) (52.5 g l(-1) Na acetate) in the fermen tation broth, although the dilution rate had to be lowered to 0.01 h(- 1). High dilution rates resulted in lactate accumulation and a decreas e in yield of acetate. The membrane bioreactor was run continuously un der varying operating conditions for 54 days without any significant p roblems.