Novel co-immobilization of thermostable isomerase and aspartase on NH2-UiO66 for efficient biosynthesis of L-aspartate from maleate

Abstract

L-aspartate is an important chemical in the food and pharmaceutical industries. Presently, it is meaningful to realize a co-immobilized multi-enzyme biocatalyst that can synthesize L-aspartate in vitro through multi-step cascade reaction. Herein, the immobilization method was first employed to investigate the ability of immobilized double enzymes, isomerase AaMaiA and aspartase AspB, to systhesize L-aspartate. The optimal temperature (50 ℃) of AaMaiA-immobilized NH2-UiO66, a metal organic framework material, was significantly superior to that of its free counterpart. Compared to free enzymes, AaMaiA@NH2-UiO66 retained 57.8% of enzyme activity and exhibited a half-life that was improved 2.59-fold at 50 ℃. The co-immobilized AaMaiA/AspB@NH2-UiO66 (AaMaiA: AspB = 6: 1, v/v) showed high protein loading (27.899 ± 1.945 mg/g) and 84.4% recovery of enzyme activity after 8 consecutive cycles. Compared to free AaMaiA/AspB, the novel AaMaiA/AspB@NH2-UiO66 exhibited far superior tolerance to organic solvents. For the first time, the prepared AaMaiA/AspB@NH2-UiO66 was successfully applied as an efficient biocatalyst and converted 1 M maleate to L-aspartate with a yield of 86.8% within 1 h. Remarkably, AaMaiA/AspB@NH2-UiO66 exhibited great potential for efficient biosynthesis of L-aspartate.