Mechanochemical biomimetic mineralization of UiO-66-NH2-immobilized cellulase for enhanced catalytic stability and efficiency

Abstract

Biomimetic mineralization is a crucial biotechnology for encapsulating enzymes within metal–organic frameworks (MOFs). While this technique is extensively employed in solvent-based systems, its applicability in mechanochemical systems remains to be explored. In addition, the structural units of MOF composition may significantly influence this process. In this study, we reported that dodecanuclear zirconium clusters act as precursors to facilitate the mechanochemical process of biomimetic mineralization, leading to the construction of cellulase@UiO-66-NH₂ (with cellulase abbreviated as Cel). The results demonstrate that dodecanuclear zirconium clusters promote the biomimetic mineralization of Cel@UiO-66-NH₂, preventing enzyme degradation by organic solvents. This approach leads to a 20% increase in enzyme activity per unit mass and a 78% improvement in the encapsulation rate. It also enhances catalytic efficiency and substrate affinity compared with Cel@UiO-66-NH₂ synthesized with hexanuclear zirconium clusters. The biomimetic mineralization was attributed to the increased local concentration of structural units of MOFs surrounding Cel, as well as transformations in chemical bonding and alterations in enzyme structure. We demonstrated the stability of Cel@UiO-66-NH₂ compared to traditional physical adsorption methods and explored its applications in the saccharification of carboxymethylcellulose and microcrystalline cellulose and the high-temperature sequential extraction of polysaccharides from Naematelia aurantialba. Our results revealed that Cel@UiO-66-NH₂ retained over 50% of its catalytic activity after eight cycles of carboxymethylcellulose saccharification and maintained 50.9% enzyme activity after five cycles of treatment with microcrystalline cellulose. In addition, we achieved a polysaccharide extraction yield of 10.35% at 70 °C.