Novel membrane processes for the enantiomeric resolution of tryptophan by selective permeation enhancements

Novel membrane processes for the effective enantioresolution of racemic mixtures have been evaluated. The incorporation of human serum albumin (HSA) in the strip solution of a permeation cell resulted in the partial optical resolution of a racemic tryptophan mixture, as the permeation of L-tryptophan, which binds to HSA more strongly, was enhanced selectively over that of D-tryptophan. A second approach in which a racemic mixture was introduced to the strip solution prior to the experiments showed better performance by selectively decreasing the flux of the more weakly bound D-tryptophan. The highest enantioselectivity of ~9.76 was achieved with a third, novel design consisting of two permeation cells in series, which can encompass the advantages of affinity dialysis. An industrial scale unit is proposed based on this concept and a suitably validated mathematical model.