An extractive fermentation process using pervaporation was studied in a 7 liter fermentor. Pervaporation was performed using a silicone membrane module and a low-acid-producing strain Clostridium acetobutylicu, B18 was used to produce butanol. In batch culture without pervaporation pH 5.5 and initial glucose concentration of 60 g/L resulted in the highest butanol productivity (0.216 g/L$.$h) with butanol yield of 0.261 Butanol flux through the membrane was best at 2.0 L/min-tubing of air flow rate In batch and fed-batch fermentation glucose consumption rate increased by 1.3 times with pervaporation.