The application of glutamic acid α-decarboxylase for the valorization of glutamic acid
作者:Tijs M. Lammens、Daniela De Biase、Maurice C. R. Franssen、Elinor L. Scott、Johan P. M. Sanders
DOI:10.1039/b913741f
日期:——
Glutamic acid is an important constituent of waste streams from biofuels production. It is an interesting starting material for the synthesis of nitrogen containing bulk chemicals, thereby decreasing the dependency on fossil fuels. On the pathway from glutamic acid to a range of molecules, the decarboxylation of glutamic acid to γ-aminobutyric acid (GABA) is an important reaction. This reaction, catalyzed by the enzyme glutamic acid α-decarboxylase (GAD) was studied on a gram scale. In this study, GAD was immobilized on Eupergit and in calcium alginate and its operational stability was determined in a buffer free system, using various reactor configurations. Immobilization was shown to increase the GAD stability. The conditions for the highest GABA production per gram of enzyme were determined by extrapolation of enzyme stability data. At 30 °C in a fed batch process this results in an average volumetric productivity of 35 kg mâ3 hrâ1. The cost of using GAD immobilized in calcium alginate was estimated as â¬5 per metric ton of product. Furthermore it was shown that the cofactor pyridoxal-5â²-phosphate (PLP) could be regenerated by the addition of a small amount of α-ketoglutaric acid to the reactor. In conclusion the application of immobilized GAD in a fed batch reactor was shown to be a scalable process for the industrial production of GABA from glutamic acid.
谷氨酸是生物燃料生产废流中的重要成分。它是合成含氮大宗化学品的良好原料,从而减少对化石燃料的依赖。在从谷氨酸到一系列分子的途径中,谷氨酸脱羧生成γ-氨基丁酸(GABA)的反应是一个重要反应。这项研究在克级规模上对这种由谷氨酸α-脱羧酶(GAD)催化的反应进行了研究。在本研究中,GAD被固定在Eupergit和海藻酸钙上,并在无缓冲系统中使用各种反应器配置来确定其操作稳定性。固定化被证明可以提高GAD的稳定性。通过外推酶稳定性数据确定了每克酶产生GABA的最高产量的条件。在30℃的补料分批过程中,这导致平均体积生产率为35千克立方米¹小时¹。估计使用海藻酸钙中固定的GAD的成本为每吨产品5欧元。此外,研究表明,通过向反应器中加入少量的α-酮戊二酸可以使辅因子吡哆醛-5'-磷酸(PLP)再生。总之,固定化GAD在补料分批反应器中的应用被证明是从谷氨酸工业化生产GABA的可扩展过程。