CONTINUOUS ACETONE-BUTANOL-ETHANOL (ABE) FERMENTATION USING IMMOBILIZED CELLS OF CLOSTRIDIUM-ACETOBUTYLICUM IN A PACKED-BED REACTOR AND INTEGRATION WITH PRODUCT REMOVAL BY PERVAPORATION

An integrated solvent (ABE) fermentation and product removal process was investigated. A stable solvent productivity of 3.5 g/L h was achieved by using cells of Clostridium acetobutylicum immobilized onto a packed bed of bonechar, coupled with continuous product removal by pervaporation. Using a concentrated feed solution containing lactose at 130 g/L, a lactose utilization value of 97.9% was observed. The integrated fermentation and product removal system, with recycling of the treated fermenter effluent containing only low amount of solvents (but lactose and acids), leads to only low acid losses. Therefore, most of the acids are converted to solvents, and this results in a high solvent yield of 0.39 g solvents/g lactose utilized. The pervaporation system provided a high product removal rate even at low solvent concentrations. A solvent membrane flux of 7.1 g/m2 h with a selectivity of 5 was achieved during these investigations. The system proved to be very reliable.