Gamma-aminobutyric acid (GABA) biosynthesis depended to a great extent on the biotransformation characterization of glutamate decarboxylase (GAD) and process conditions. In this paper, the enhancing effect of D101 macroporous adsorption resin (MAR) on the GABA production was investigated based on the whole-cell biotransformation characterization of Enterococcus faecium and adsorption characteristics of D101 MAR. The results indicated that the optimal pH for reaction activity of whole-cell GAD and pure GAD was 4.4 and 5.0, respectively, and the pH range retained at least 50% of GAD activity was from 4.8 to 5.6 and 4.0–4.8, respectively. No substrate inhibition effect was observed on both pure GAD and whole-cell GAD, and the maximum activity could be obtained when the initial L-glutamic acid (L-Glu) concentration exceeded 57.6 mmol/L and 96.0 mmol/L, respectively. Besides, GABA could significantly inhibit the activity of whole-cell GAD rather than pure GAD. When the initial GABA concentration of the reaction solution remained 100 mmol/L, 33.51 ± 9.11% of the whole-cell GAD activity was inhibited. D101 MAR exhibited excellent properties in stabilizing the pH of the conversion reaction system, supplementing free L-Glu and removing excess GABA. Comparison of the biotransformation only in acetate buffer, the GABA production, with 50 g/100 mL of D101 MAR, was significantly increased by 138.71 ± 5.73%. D101 MAR with pre-adsorbed L-Glu could significantly enhance the production of GABA by gradual replenishment of free L-Glu, removing GABA and maintaining the pH of the reaction system, which would eventually make the GABA production more economical and eco-friendly.

中文翻译：

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大孔吸附树脂对全细胞生物转化系统中粪肠球菌产生γ-氨基丁酸的影响。

γ-氨基丁酸（GABA）的生物合成在很大程度上取决于谷氨酸脱羧酶（GAD）的生物转化特性和工艺条件。本文基于粪肠球菌的全细胞生物转化特性和D101 MAR的吸附特性，研究了D101大孔吸附树脂（MAR）对GABA产生的促进作用。结果表明，全细胞GAD和纯GAD反应活性的最佳pH分别为4.4和5.0，保留了至少50％GAD活性的pH范围分别为4.8至5.6和4.0-4.8。在纯GAD和全细胞GAD上均未观察到底物抑制作用，初始L时可获得最大活性。-谷氨酸（L -Glu）的浓度分别超过57.6mmol / L和96.0mmol / L。此外，GABA可以显着抑制全细胞GAD的活性，而不是纯GAD的活性。当反应溶液的初始GABA浓度保持在100 mmol / L时，全细胞GAD活性的33.51±9.11％被抑制。D101 MAR在稳定转化反应系统的pH值，补充游离L -Glu并去除过量的GABA方面表现出优异的性能。仅在乙酸盐缓冲液中进行生物转化的比较，使用50 g / 100 mL D101 MAR的GABA产量显着提高了138.71±5.73％。带有预先吸附的L -Glu的D101 MAR可通过逐渐补充游离L来显着提高GABA的产生-Glu，除去GABA并保持反应体系的pH值，这最终将使GABA生产更加经济和环保。