Selective recovery of histidine-containing dipeptides based on metal affinity interactions using chemically modified dextran in combination with ultrafiltration

A recovery system using metal affinity interactions in combination with ultrafiltration (UF) membrane separation was developed for nutraceutically important histidine-containing dipeptides (HCDPs) such as carnosine (Car) and anserine (Ans). Cu(II)-immobilized, chemically modified dextran bearing an iminodiacetic acid group (Cu(II)IDA-EGDE-Dex) was prepared as a complexing material for HCDPs. After the water-soluble Cu(II)IDA-EGDE-Dex captures Car in an aqueous solution, the complex is separated from the aqueous solution with the UF membrane. The recovery of Car using Cu(II)IDA-EGDE-Dex reaches equilibrium within one hour, which is much faster than metal affinity adsorption using a polystyrene chelating adsorbent. Cu(II)IDA-EGDE-Dex captures Car via metal affinity interactions in the presence of 100 mM NaCl, under which conditions the chemically modified dextran does not capture Car. Histidine and the HCDPs were selectively recovered by Cu(II)IDA-EGDE-Dex from a mixed solution containing Car, Ans and 17 amino acids, and from a model solution of bonito broth. The immobilized Car was efficiently eluted from Cu(II)IDA-EGDE-Dex using acetic acid as an eluent.