Optically pure D-glutamine was prepared by biotransformations of DL-glutamine manufactured by chemical synthesis. Firstly, DL-glutamine was synthesized from DL-glutamic acid on larger scale. Protected DL-glutamic acid was prepared by using inexpensive phthaloyl as protecting group. Then N-phthaloyl-DL-glutamic acid anhydride was synthesized with protected DL-glutamic acid and acetic anhydride under reflux for 15 min. Un-der ambient temperature and normal pressure, N-phthaloyl-DL-glutamine was produced by reacting N-phthaloyl-DL-glutamic acid anhydride with 2 mol/L ammonia solution. After the phthaloyl was removed from the intermediate with 0.5 mol/L hydrazine hydrate under ambient temperature for 48 h DL-glutamine mixture was obtained in 57% yields. L-Glutamine in the racemic mixture was selectively decarboxylated to 4-aminobutanamide by the decarboxylase of E. coli AS1.505. Under the following conditions: temperature of 37 ℃, reaction time of 8 h, pH of 4.8, substrate concentration of 30 g/L, D-glutamine was efficiently produced.

Key words: decarboxylase, DL-glutamic acid, D-glutamine