Efficient Optical Resolution of DL-Glutamate by Combining Enzymatic Racemization and Preferential Crystallization

Abstract

Preferential crystallization is a method for obtaining a pure enantiomer from a racemic solution However, only a 50% maximum yield is obtained when the chiral molecules are not racemized in the solution. In this study, preferential crystallization of monoammonium glutamate (MAG) was performed in the presence of glutamate racemase, a racemization enzyme. The yield and optical purity of L-MAG were 49.4% and 13.8% ee, respectively, without enzymatic racemization. However, the yield and purity were improved to 97.7% and 97.4% ee, respectively, using glutamate racemase immobilized on chitosan beads. Thus, the combination of preferential crystallization and enzymatic racemization significantly improved the purity and yield. Moreover, a crystallization device with an immobilized enzyme can be expected to become a method for optically resolving chiral molecules with high efficiency.

Keywords

• Cooling crystallization
• Amino acid
• Preferential crystallization
• Glutamate racemase