Abstract: A system using membranes for separating a desired component from a liquid or gas mixture to obtain a high-concentration organic solvent, such as in a plant for fermenting a biomass feedstock (e.g., corn or sugarcane) to produce ethanol. A module for removing water from the ethanol/water mixture comprises multiple vessels or elements connected together in series and supported by a frame. Each element includes a number of flow tubes concentrically enclosing a tubular membrane leaving an annular space between the membrane's outer wall and the flow tube's inner wall. The preferred membrane is a hollow ceramic (e.g., zeolite) tube. An ethanol/water vapor is passed through the space between the tube walls, and a vacuum is pulled on the membrane's hollow core. Water molecules selectively move through the membrane. Multiple passes through a series of elements having the concentric tubes and membranes gradually reduces the water content of the ethanol.