本研究主要探討紅豆芽中麩胺酸脫羧酶 (GAD) 最適化生產γ-胺基丁酸 (GABA) 之條件。在固定酵素受質比值為0.0136、CaCl2 0.25 mM及反應時間1 h之下，以反應曲面法探討GAD最適化生產GABA之條件包括反應溫度、pH及pyridoxal phosphate (PLP) 濃度，其探討範圍分別為28.6~45.5℃ 、pH 6.32~9.68以及0.032~0.368 mM PLP，經由反應曲面回歸分析顯示，最適化生產條件為37.2℃ 、pH 7.6、0.208 mM PLP，可得最高的GABA產量326.7 mg/L，依照上述最適化條件進行驗證試驗，預測值在試驗值的95%信心度區間之內。接著利用生物反應器分離產物GABA並回收仍具有活性的GAD以持續轉換麩氨酸(Glu)生產GABA，回收利用GAD 2次後的生產率為197.3 mg GABA/mg protein是批次生產的2.89倍。儲存安定性試驗發現在4℃ 與-20℃ 保存半年均仍保有70%的GAD活性。

Response surface methodology was applied to evaluate the independent variables including reaction temperature 28.6~45.5oC, pH 6.32~9.68 and pyridoxal phosphate (PLP) concentration 0.032~0.368 mM under fixed enzyme to substrate ratio of 0.0136, 0.25 mM CaCl2 and reaction time 1 h. Based on response surface regression analysis procedure, the optimum reaction conditions for maximizing GABA production of 326.7 mg/L were 37.2oC, pH 7.6 and 0.208 mM PLP. The maximum predicted value could be achieved within 95% confidence interval of experimental values. Furthermore, bioreactor was employed to convert glutamate with GAD into GABA and to recycle the GAD. The productivity of bioreactor was 197.3 mg GABA/mg protein, which was 2.89 fold than that of batch reactor after reusing the GAD for twice. The result of storage stability test indicated that 70% GAD activity was maintained after half year storage under both 4oC and -20oC.