A catalase-like nanozyme of high activity and stability in acidic solutions for enzyme immobilization and chemoenzymatic cascade conversion of glucose to gluconic acid

Gluconic acid is widely used in food and pharmaceutical. However, its bio-synthesis by glucose oxidase (GOx) is blocked by depletion of dissolved O 2 , reduction of pH value, and accumulation of hydrogen peroxide (H 2 O 2 ). To remove the by-products and replenish O 2 , developing a nanozyme with high catalase (CAT)-like activity and stability under acidic conditions is a prescription. Herein, we developed a manganese-based nanozyme (ps-MnO x -BSA) through a stepwise strategy and encapsulated it in Fe-doped zeolitic imidazolate framework-8 (FZ). The as-prepared ps-MnO x -BSA@FZ (MFZ) exhibited not only high stability and CAT-like activity but also exceptionally no peroxidase-like activity at pH 5.5. Thereafter, GOx@MFZ was fabricated by the immobilization of GOx on MFZ and utilized for gluconic acid synthesis with a yield of 98.3 % within 30 min. GOx@MFZ retained 92.3 % of its initial activity after six batches. This work provided a novel strategy for the design of acid-resistant CAT-like nanozyme toward sustainable gluconic acid production.