Acetone-butanol-ethanol (ABE) fermentation by combining a PDMS membrane bioreactor and Clostridium acetobutylicum was studied, and a long continuous and closed-circulating fermentation (CCCF) system has been achieved. Two cycles of experiment were conducted, lasting for 274 h and 300 h, respectively. The operation mode of the first cycle was of fermentation intermittent coupling with pervaporation, and the second cycle was of continuous coupling. The average cell weight, glucose consumption rate, butanol productivity and butanol production of the first cycle were 1.59 g L-1, 0.63 g L-1 h(-1), 0.105 g L-1 h(-1) and 28.03 g L-1, respectively. Correspondingly, the four parameters of the second cycle were 1.68 g L-1, 1.12 g L-1 h(-1), 0.205 g L-1 h(-1) and 61.43 g L-1, respectively. The results indicate the fermentation behaviors under continuous coupling mode were superior to that under intermittent coupling mode. Besides, two peak values were observed in the time course profiles, which means the microorganism could adapt the long CCCF membrane bioreactor system. (C) 2012 Elsevier Ltd. All rights reserved.