High-performance glucose isomerase detection enabled by self-cascade copper oxide nanozyme system

Glucose isomerase (GI), also known as D-xylose isomerase, plays a crucial role in converting glucose to fructose, widely applied in the food and agricultural industries. However, current GI activity detection methods suffer from limited sensitivity and operational complexity. Herein, we propose a novel detection strategy by coupling GI-catalyzed isomerization with a self-cascade copper oxide (CuO) nanozyme system. This cascade leverages the dual fructose oxidase-like and peroxidase-like activities of CuO nanozymes to achieve efficient signal amplification. The method offers a broad linear range (0.3-9.375 U/mL) and a low detection limit (0.11 U/mL), outperforming existing detection techniques. Spiking recovery experiments were performed on the glucose isomerase extract derived from Escherichia coli cultures, the culture medium, and commercial glucose isomerase preparations, yielding recoveries ranging from 86.22 % to 107.34 %. Given its high sensitivity, simplicity, and practicality, this method shows great promise for screening GI-producing bacterial strains and for the detection of GI activity in various applications.