A mathematical model was developed to describe a fed-batch acetone-butanol-ethanol (ABE) fermentation with simultaneous pervaporation. The model predicted satisfactorily batch or fed- batch fermentation with or without pervaporation by introducing a parameter reflecting cell activity loss during fed-batch fermentation with pervaporation. The model also predicted the effect of membrane area, membrane thickness, and sweep air flow rate on glucose consumption rate and residual butanol concentration in the fermentation broth. Glucose con- sumption rate increased by 30% by either doubling the membrane area or decreasing mem- brane thickness by half.