Selective Transport of a Peptide from Its Mixture with an Amino Acid Using a Supported Liquid Membrane Process

Some experimental results on the separation of a peptide from a mixture of peptide and amino acid through a continuous supported liquid membrane process are described. As a model system a mixture of tryptophan (Trp, an amino acid) and tryptophan-leucine (Trp-Leu, a dipeptide) was chosen. The liquid membrane contained an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (Aerosol OT/AOT), as a carrier dissolved in oleyl alcohol, as an organic solvent, supported on a commercial grade support (Celgard 2500). The liquid-liquid extraction experiments were carried out to study the influence of feed pH, feed and strip flow rates, and feed and carrier concentrations on the selective transport of Trp-Leu from its mixture with Trp. At pH 4–5 the transport rate of Trp-Leu was significantly higher than that of Trp. The increase in flow rate up to a value of 40 mL/h did not effect the selective removal of Trp-Leu. The flux rate increased with an increase of the carrier concentration up to 20% AOT, but the selectivity for Trp-Leu was highest at 10% AOT. An increase of Trp concentration up to 10-fold had little effect on the flux rate of Trp-Leu. The stability of SLM system in continuous removal of Trp-Leu from a single component system and from a binary mixture with Trp was studied. The effect of a competitive component did not alter significantly the flux rate and long-time performance in continuous operation. A procedure for regenerating SLM was examined, and the regenerated SLM performed as good as the freshly prepared one.