Performance of the ABE fermentation and integrated product recovery by cyclic vacuum was investigated in a 14-1 bioreactor containing initial glucose concentration of 60 g l(-1) at 35 degrees C. The cyclic operation consisted of 2 h-vacuum-cycles separated by 4 h-fermentation intervals at atmospheric pressure. Application of periodic vacuum sufficed to eliminate hutanol inhibition of Clostridium beijerinckii 8052 culture, which tolerated alternate vacuum and atmospheric pressures. A 39% reduction in the energy requirement for acetone butanol ethanol (ABE) fermentation and in situ recovery by vacuum was achieved by changing the mode of vacuum operation from continuous (24 h vacuum time) to cyclic (12 h vacuum time). Analysis of the overall energy consumption for ABE fermentation and recovery (vacuum fermentation + distillation) demonstrated that cyclic vacuum ABE fermentation is more energy efficient than the conventional batch fermentation. (C) 2012 Elsevier Ltd. All rights reserved.