Separation of amino acids mixtures containing tyrosine in electromembrane system

The principal distinction of tyrosine transport in the electromembrane system is revealed. It lies in the absence of electromigration of this amino acid through the cation-exchange membrane MC-40 in a wide range of current density. This is true for any pH value, including the region where tyrosine exists mainly in the form of cations. Only insignificant diffusive transfer of this aromatic amino acid (pI 0/5.63) is observed. At the same time the dependence of the flux through the anion-exchange membrane on the current density has the traditional form for amino acids with the maximum corresponding to the limiting current. On the basis of the revealed regularity of tyrosine transport, we study the possibility of its separation from the basic amino acid (arginine or histidine) that migrates actively through the cation-exchange membrane.

The principal distinction of the aromatic amino acid transport during the electrodialysis is found. Tyrosine does not migrate through the cation-exchange membrane at any pH value. The conjugative transport of this amino acid with mineral ions has not been observed either. Taking into account the common nonlinear effects of amino acids transfer in the electromembrane system, as well as the peculiarities of the aromatic amino acid, it is possible to provide the tyrosine separation. The separation coefficients in tyrosine Á arginine and tyrosine Á histidine systems have been calculated. The recovery values have been determined. In most cases, one cannot achieve the complete separation of amino acids with similar isoelectric points during the electrodialysis. However, it should be stressed that the electrodialysis allows us to regulate the ratio of various amino acids in complex solutions, such as parenteral nutrition solutions. To conclude, we can say that electrodialysis creates great opportunities in the field of amino acids separation and purification, which have not yet been used to a full extent. Nomenclature C CA CB / CA / CB Сperm С0 ilim J S Sc t V ηη ion-exchange membrane effective area (m2) separation coefficient sampling time (s) probe volume (m3) recovery ratio