Application of Membrane Technologies for Biomolecules Separation by Affinity Binding to Recovered Stereospecific Ligands

Many of pharmaceutical compounds are stereoisomer molecules that compose of at least one chiral carbon. Frequently, each enantiomer provides different biological activities and therefore, a highly selective and cost effective separation technique for chiral molecules is highly demanded. Affinity ultrafiltration (UF) is one type of membrane-based technology which incorporates the ability of stereoselective ligand to selectively bind one enantiomer. Compared to other separation technologies, a membrane-based technology has been regarded as more cost effective, suitable for continuous operation and more easily scaled-up. Despite of the benefits of membrane technology for chiral separation, it has not been implemented for large scale application yet with the recovery and reusability of ligand has been considered as one of the limiting factors.

 In this study, we intended to investigate the separation performance of _D,L-tryptophan by utilizing Human Serum Albumin (HSA) as the stereoselective ligand. HSA was chosen due to its ability to undergo a structural change under different solution pH. The trend in _D,L-tryptophan separation performances after several regeneration cycles of HSA was analyzed and it was found that the native and recovered HSA molecules exhibit a similar _D,L-tryptophan separation factor of 5-7. Other than reusability, a high recovery of stereoselective ligand after each separation process is also substantial. For this purpose, low fouling tendency polyethersulfone (PES) hollow fiber membranes with a high rejection of HSA was fabricated by a non solvent induced phase inversion process. We observed that by controlling membrane pore size and hydrophilicity, a high recovery percentage of HSA of above 80% could be attained.