Using deep eutectic solvents to enhance immobilized glutamate decarboxylase for γ-aminobutyric acid synthesis

Deep eutectic solvents (DESs) can improve the catalytic efficiency of enzymes. The effect of DESs on the biocatalytic decarboxylation of sodium glutamate to γ-aminobutyric acid (GABA) by site-directed immobilized enzymes was studied. 1.5% choline chloride/glycerol (ChCl/Gly, molar ratio, 2:1) increased the catalytic rate of the site-directed immobilized enzyme by 14%. In ChCl/Gly-containing systems, the Km, kcat, activity and activation energy of the enzyme were 3.17 mM, 48.86 s-1, 48.41 U/mg and 28.69 kJ/mol, respectively. Furthermore, ChCl/Gly resulted in the change of the secondary structure of the immobilized enzyme. The optimum pH and temperature of the enzymatic reaction were 3.0 and 60 °C in ChCl/Gly-containing systems, respectively. Finally, GABA was afforded in a yield of 78.3% at a substrate concentration of up to 180 mM using a fed-batch strategy. This study provides a green and promising method for efficient GABA biosynthesis.