Reactive extraction of biomolecules using hollow-fibre modules

Separation and purification of biomolecules from a fermentation broth or from a natural media involve many steps. Each step contributes to the product cost and product loss. The selective separation of any "target" product from the complex mixture can be accomplished by allowing a reaction between the molecule and a carrier. The carrier is dissolved in an organic phase that preferentially dissolves the reactant-carrier complex and this method is known as "reactive extraction". This method has the potential to overcome many disadvantages of the conventional separation techniques and could minimize the product cost and loss. In this report, the application of this method for the separation of some pharmaceutical products including amino acids and dipeptides is presented. The experimental system involves a hollow-fibre membrane module which has a shell-and-tube configuration and allows flow of two solutions in the fibre and shell sides. The feed and organic solutions are circulated on the fibre side and shell side, respectively. The target solute molecules diffuse to the aqueous-organic interface, forms a complex with the carrier; the carrier-solute complex is transported to the shell side, where it can be recovered. The results of extraction into the organic phase are presented for a variety of process conditions. The stability of the reactive extraction process in long-term operation is mentioned. The aim of this study was threefold: (i) To examine the extraction percentage of the solutes at various process conditions (e.g. feed pH and organic phase concentration) with a commercially available membrane module; (ii) To derive simple modelling equations for the determination of the overall mass transfer coefficient from straightforward use of the experimental data; (iii) To test an "industrial" sample for removing undesirable solutes (e.g. peptides etc.).