Application of cross‐linked β‐cyclodextrin polymer for adsorption of aromatic amino acids

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Abstract
β‐Cyclodextrin (β‐CyD) was cross‐linked by hexamethylene diisocyanate and the polymer was investigated for adsorption of aromatic amino acids (AAA) from phosphate buffer. High adsorption rates were observed at the beginning and the adsorption equilibrium was then gradually achieved in about 45 min. The adsorption of AAA decreased with the increase of initial concentration and also temperature. Under the same conditions, the adsorption efficiencies of AAA were in the order of L‐tryptophan (L‐Trp) > L‐phenylalanine (L‐Phe) > L‐tyrosine (L‐Tyr). Much higher adsorption values, up to 52.4 and 43.0 mg/g for L‐Trp and L‐Phe, respectively, at 50 mmol/L and 3.2 mg/g for L‐Tyr at 2 mmol/L, were obtained with the β‐CyD polymer at 37 °C. It was shown that the adsorption of AAA on the β‐CyD polymer was consistent with the Freundlich isotherm equation. The adsorption of mixed aromatic amino acids and branched‐chain amino acids (BCAA) showed that AAA were preferentially adsorbed with adsorption efficiencies 10–24%, while those of BCAA were lower than 2%. It seems that the structure and hydrophobicity of amino acid molecules are responsible for the difference in adsorption, by influencing the strength of interactions between amino acid molecule and the polymer. Copyright © 2005 John Wiley & Sons, Ltd.