Enzymatic production of α-ketoglutaric acid from l-glutamic acid via l-glutamate oxidase

In this study, a novel strategy for α-ketoglutaric acid (α-KG) production from l-glutamic acid using recombinant l-glutamate oxidase (LGOX) was developed. First, by analyzing the molecular structure characteristics of l-glutamic acid and α-KG, LGOX was found to be the best catalyst for oxidizing the amino group of l-glutamic acid to a ketonic group without the need for exogenous cofactor. Then the LGOX gene was expressed in Escherichia coli BL21 (DE3) in a soluble and active form, and the recombinant LGOX activity reached to a maximum value of 0.59 U/mL at pH 6.5, 30 °C. Finally, the maximum α-KG concentration reached 104.7 g/L from 110 g/L l-glutamic acid in 24 h, under the following optimum conditions: 1.5 U/mL LGOX, 250 U/mL catalase, 3 mM MnCl2, 30 °C, and pH 6.5.