双酶级联生物合成D-赖氨酸

Production of D-lysine Catalyzed by a Two-step Biocatalytic Cascade of Amino Acid Racemase and Lysine Decarboxylase

摘要:

建立了氨基酸消旋酶和赖氨酸脱羧酶双酶级联高效生产D-赖氨酸的方法：利用氨基酸消旋酶全细胞催化消旋L-赖氨酸得到DL-赖氨酸，去除氨基酸消旋酶后再利用赖氨酸脱羧酶全细胞对消旋产物生物拆分，得到D-赖氨酸。经考察双酶级联催化的最佳条件为：反应温度40 ℃，0.2 mol/L磷酸钾缓冲溶液（pH 5.8），底物L-赖氨酸质量浓度为50 g/L，氨基酸消旋酶全细胞和赖氨酸脱羧酶全细胞质量浓度均为10 g/L，4 mmol/L磷酸吡哆醛，0.1 g/L Triton-X 100，反应时间12 h，其中消旋反应2 h和脱羧反应10 h，最终D-赖氨酸收率达42%，对映体过量值（e.e.值）=98%。

Abstract:

This study indicates the design and investigation of two continuous reaction processes for efficient production of D-lysine including an enzymatic racemization step and an enzymatic decarboxylation step. Firstly, L-lysine was racemized to the DL-lysine by whole cells containing amino acid racemase (AAR) ; then eliminating AAR and adding whole cells containing lysine decarboxylase (LDC), L-lysine in the mixture was selectively decarboxylated to 1, 5-pentanediamine and CO2; finally D-lysine was separated from mixture by isoelectric point crystallization and ion exchange resin. An optimal condition of the cascaded enzyme system is as follows: reaction temperature 40 oC, 0.2 mol/L of potassium phosphate buffer (pH=5.8), 50 g/L of L-lysine, 10 g/L whole cells of AAR and LDC, respectively, 4 mmol/L of PLP, 0.1 g/L of Triton-X 100. Under the optimal conditions, after 12 h including 2 h of racemization step and 10 h of decarboxylation step the enzymatic catalysis reaction was completed, and the yield of D-lysine could reach 42%, enantiomeric excess (e.e.) =98%.