1,3-Propanediol was separated from aqueous solutions by pervaporation through an X-type zeolite membrane on a gamma -Al2O3 support. Binary, ternary, and quaternary mixtures and a cell-free fermentation broth were used. At 308 K. the total fluxes for the quaternary solution and the fermentation broth were 2.1 and 1.2 kg/(m(2) h), respectively. Prevaporation fluxes of all components increased with temperature, but the water flux increased at the fastest rate. From 308 to 328 K, the 1,3-propanediol/glycerol selectivity for the quaternary model solution increased from 59 to 67; it increased from 61 to 110 for the broth. The 1,3-propanediol/glucose selectivity increased from 1900 to 2200. The 1,3-propanediol/glycerol selectivity was mainly controlled by preferential adsorption, and the 1,3-propanediol/glucose selectivity it as mainly controlled by differences in diffusion rates. The membrane was stable during the pervaporation of the quaternary mixture for at least one week. In contrast, after 60 h, the broth started to foul the membrane, and the 1,3-propanediol permeate concentration decreased. The membrane was regenerated by calcination at 653 K for 4 h.