One of the major limitations in butanol fermentation is the end product toxicity which limits the butanol yield and increases the downstream processing costs. In this work, a range of non-ionic surfactants (Triton X 114, L64, L62LF, L61, and L62) was tested to enhance the acetone butanol (AB) production, and to extract and separate butanol from the fermentation broth. In biocompatibility tests, a volume fraction of 3% L62, L62LF, and L61 did not show inhibition to AB production in 72-h fermentation using Clostridium pasteurianum. Three-percent L64 reduced the AB yield whereas Triton X 114 (3%) inhibited the AB production. Further optimization with L62 at 6% resulted in a butanol yield of 225% higher than the control. The partition coefficient of butanol in L62-water two phase systems in cloud point extraction ranged from 3 to 4. A considerable enrichment of butanol (6 times) was achieved in the surfactant-rich phase over the control. In addition, the downstream process volume was reduced by 4-6 times. Butanol was separated from the surfactant-rich phase (obtained from model system) by evaporation between 120 and 130 degrees C. The butanol was enriched in the condensate reaching a concentration of 106.8 g l(-1) under which butanol automatically separated into two phases. The L62 was recovered by evaporation and reused for 3 times without affecting the partition coefficient, volume reduction, and butanol recovery in the surfactant-rich phase. The results demonstrated that the L62 not only significantly enhanced the butanol production but also functioned as a good extractant for separating butanol from the fermentation broth. (C) 2012 Elsevier Ltd. All rights reserved.