Various possibilities of the application of membrane-based solvent extraction (MBSE) and pertraction in recovery and separation of organic acids, and in biotransformations are discussed. A short overview of the subject literature is presented. Factors, which have to be considered in the development of MBSE application, will be discussed. Hybrid processes employing MBSE will be covered as well. Mass-transfer characteristics of hollow fiber contactors for MBSE of organic acids are presented. The kinetics of formation and decomposition of the permeant-extractant complex may influence greatly the mass-transfer rate and should be taken into account in modelling. A case study on recovery of 5-methyl-2-pyrazinecarboxylic acid (MPCA) by simultaneous MBSE and membrane-based solvent stripping shows potential of this process. Optimised process parameters for MPCA are suggested on bases of simulations. Outlook for future applications of HF contactors in extraction separations is discussed and potential for progress is envisaged, especially for higher value acids and integrated or hybrid reaction-separation systems. (C) 2004 Elsevier B.V. All rights reserved.