SELECTIVE SORPTION OF D-AND L-TRYPTOPHAN BY CHITOSAN AND ITS N-ACYLATED DERIVATIVES

Abstract

The chemical modification of chitosan by N-acylation of the amino groups with various carboxylic anhydrides was performed to introduce a new functionality. The equilibrium sorption of tryptophan by the N-acylated chitosan gels was determined at 30°C. The N-dodecanoyl derivative has a lower equilibrium sorption as compared with the original chitosan resulting from the more compact structure of the gel. On the other hand, the N-octadecanoyl derivative, which can not form a compact structure due to a longer side chain, has a higher sorptivity of tryptophan. The N-octadecanoyl chitosan gel having a degree of substitution of 0.45, selectively sorbs L-tryptophan from an aqueous 1:1 D, L-tryptophan solution of 1.015×10^-2 mol•dm³ giving a ratio of sorption of L/D ≈60.