Efficient cascade conversion of starch to gluconic acid by a chemoenzymatic system with co-immobilized Au nanoparticles and enzymes

Abstract

A chemoenzymatic cascade system (GA&GOx@Au–SiO₂) was fabricated by immobilizing Au nanoparticles onto mesoporous silica nanoparticles (SiO₂) followed by the co-immobilization of glucoamylase (GA) and glucose oxidase (GOx) for the efficient production of gluconic acid from starch. The proximity effect of Au nanoparticles, GOx, and GA allowed rapid transport of the reaction intermediates (glucose and H₂O₂) and timely removal of H₂O₂ that was harmful to the enzymes, thus improving the yield of gluconic acid as well as stability of the biocatalysts. The yield of gluconic acid with GA&GOx@Au–SiO₂ reached 97.8% within 30 min, much higher than the control systems for comparison. Besides, GA&GOx@Au–SiO₂ maintained 83.9% of initial activity after 10 cycles of usage, also higher than that without immobilized Au nanoparticles (57.5%). Such a chemoenzymatic cascade system provides a new strategy for improving the performance of enzymatic reactions with H₂O₂ generation.