In-situ honeycomb spheres for enhanced enzyme immobilization and stability

Abstract

This paper presents a promising heterogeneous biocatalyst-immobilized cellulase system, which can facilitate the targeted catalytic conversion of biomass to reducing sugars. Magnetic Zeolite Imidazole Framework-8/chitosan (Fe3O4/ZIF-8/CS, FZC) hybrid honeycomb microspheres were synthesized to immobilize cellulase using an in-situ growth strategy. The enhancement of immobilization efficiency induced by each constituent of the composite carrier was explored. This exploration was grounded in varying combinations of components within the honeycomb composite spheres, revealing the indispensability of ZIF-8. Through in-situ assembly, the composite material presents a microsphere with an internal honeycomb structure and multilevel pores. Effective immobilization, temperature-responsive conformational change, and cyclic stability were achieved due to the scaling effect of the channel, extensive specific surface area, and abundant amino group interactions enable immobilized enzymes to maintain excellent performance under challenging operating conditions, demonstrating an enhanced structure-performance relationship. With the obtained immobilized cellulase, we achieved a high load (461.67 mg/g) of cellulase and a significant reducing sugar yield (328.39 mg/g) from corncob waste. In addition, we investigated the enhancement effect of thermal activation on the immobilized enzyme activity of composite carrier. The results showed that the appropriate heat treatment was conducive to the activation of FZC immobilized enzyme with a reducing sugar yield 1.61 times higher than that of the control. The strategy provided in this study promotes the development of immobilized biocatalysts and provides a useful reference for the further design of biocatalytic systems.