Objectives

γ-amino butyric acid (GABA) is a non-protein amino acid, considered a potent bioactive compound. This study focused on biosynthesis of food-grade GABA by immobilized glutamate decarboxylase (GAD) from Lactobacillus plantarum in the rice vinegar and monosodium glutamate (MSG) reaction system.

Results

The gene encoding glutamate decarboxylase (GadB) from L. plantarum has been heterologously expressed in Lactococcus lactis and biochemically characterized. Recombinant GadB existed as a homodimer, and displayed maximal activity at 40 °C and pH 5.0. The K_m value and catalytic efficiency (k_cat/K_m) of GadB for L-Glu was 22.33 mM and 62.4 mM⁻¹ min⁻¹, respectively, with a specific activity of 24.97 U/mg protein. Then, purified GadB was encapsulated in gellan gum beads. Compared to the free enzyme, immobilized GadB showed higher operational and storage stability. Finally, 9.82 to 21.48 g/L of GABA have been acquired by regulating the amounts of catalyst microspheres ranging from 0.5 to 0.8 g (wet weight) in 0.8 mL of the designed rice vinegar and MSG reaction system.

Conclusions

The method of production GABA by immobilized GadB microspheres mixed in the rice vinegar and MSG reaction system is introduced herein for the first time. Especially, the results obtained here meet the increased interest in the harnessing of biocatalyst to synthesize food-grade GABA.

中文翻译：

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植物乳杆菌固定化谷氨酸脱羧酶在米醋和味精体系中生产食品级γ-氨基丁酸

目标

γ-氨基丁酸 (GABA) 是一种非蛋白质氨基酸，被认为是一种有效的生物活性化合物。本研究的重点是在米醋和味精 (MSG) 反应体系中，通过固定化植物乳杆菌的谷氨酸脱羧酶 (GAD) 生物合成食品级 GABA 。

结果

来自植物乳杆菌的编码谷氨酸脱羧酶 (GadB) 的基因已在乳酸乳球菌中异源表达并进行生化表征。重组 GadB 作为同型二聚体存在，在 40 °C 和 pH 5.0 时显示出最大活性。GadB 对L -Glu的K _m值和催化效率（k _cat / K _m）为 22.33 mM 和 62.4 mM ^-1  min ^-1分别具有 24.97 U/mg 蛋白质的比活。然后，将纯化的 GadB 封装在结冷胶珠中。与游离酶相比，固定化 GadB 显示出更高的操作和储存稳定性。最后，通过在 0.8 毫升设计的米醋和味精反应体系中调节 0.5 至 0.8 克（湿重）的催化剂微球量，获得了 9.82 至 21.48 克/升的 GABA。

结论

本文首次介绍了在米醋和味精反应体系中混合固定化GadB微球生产GABA的方法。特别是，这里获得的结果满足了人们对利用生物催化剂合成食品级 GABA 的兴趣。