LIGAND-EXCHANGE CHROMATOGRAPHY OF AMINO-ACID ENANTIOMERS AND ITS APPLICATION TO THE BIOTRANSFORMATION OF DL-ASPARTIC ACID BY PSEUDOMONAS-DACUNHAE

The separation of the D and L enantiomers of eighteen essential alpha amino acids has been investigated by ligand-exchange chromatography (L EC). The effect of column temperature on the retention times and resol ution of individual amino acid enantiomers has been studied by varying the temperature from 25 to 50-degrees-C for a mobile phase containing Cu2+ ions. By use of a temperature of 50-degrees-C and Zn2+ in the mo bile phase, eight of the eighteen amino acid enantiomers can be resolv ed sufficiently well for practical application. Only phenylalanine, ty rosine, and tryptophan can be separated by use of Ni2+ as complexation metal at 50-degrees-C. LEC has been used to monitor the decarboxylati on of racemic DL-aspartic acid by Pseudomonas dacunhae. Analysis of DL amino acid enantiomers in different media was performed at column tem peratures of 30 and 50-degrees-C by addition of 0.125 mM Cu2+ to the a queous mobile phase. It was found that the analytical performance is m ost dependent on the identity of the metal used for complexation; the concentration of the metal was of secondary importance and the column temperature less important still.