Sorption and pervaporation experiments to study the methanol/methyl tert-butyl ether (MTBE) separation, were carried out with poly(3-hydroxybutyrate) (PHB) membranes. Single component tests showed that PHB membranes were methanol selective and pervaporation fluxes increased with temperature, as expected. However, permeability coefficients showed quite different behavior for each component. Mixture pervaporation results showed an increase in flux and separation factor with temperature, and a significant enhancing of flux due to MTBE. Sorption mixture behavior exhibited a maximum as feed methanol concentration increased. The same tendency was reflected in pervaporation permeability coefficients with the maximum value occurring near azeotropic concentration. The results were discussed in terms of physico-chemical properties of the system, as polymer crystallinity and thermal transitions, solubility parameters, component kinetic diameters, plasticization and coupling effects. Very high fluxes and selectivities up to 9 indicate promising prospects for the PHB membranes. (C) 2010 Elsevier B.V. All rights reserved.