Optical resolution of α-amino acids through enantioselective polymeric membranes based on polysaccharides

For the optical resolution of α-amino acids, enantioselective membranes crosslinked were prepared using sodium alginate (SA) and chitosan (CS) as membrane materials. The characteristics of the membranes in terms of their chemical structure and swelling indices were analyzed. The permselective properties of the membranes in the separation of optical isomers of α-amino acids were studied using aqueous solutions of tryptophan and tyrosine as feed solutions. The employed membrane process was a pressure driven process using a low Δp such as 1 or 2 kgf/cm2. Effects of degree of crosslinking, feed concentration, operating pressure and different kinds of feed solutions on the membrane performances were studied. When a chitosan membrane with 70% of swelling index was used for the optical resolution of tryptophan racemic mixture (0.49 mmol/l aqueous solution), over 98% of enantiomeric excess (e.e.) and 6.4 mg/(m2 h) of flux were obtained.