Molecularly Imprinted Synthetic Glucosidase for the Hydrolysis of Cellulose in Aqueous and Nonaqueous Solutions

Abstract

Molecular imprinting is a powerful and yet simple method to create multifunctional binding sites within a cross-linked polymer network. We report a new class of synthetic glucosidase prepared through molecular imprinting and postfunctionalization of cross-linked surfactant micelles. These catalysts are protein-sized water-soluble nanoparticles that can be modified in multiple ways. As their natural counterparts, they bind a glucose-containing oligo- or polysaccharide. They contain acidic groups near the glycosidic bond to be cleaved, with the number and distance of the acid groups tuned systematically. Hydrolysis of cellulose in a key step in biomass conversion but is hampered by the incalcitrance of the highly crystalline cellulose fibers. The synthetic glucosidases are shown to hydrolyze cellobiose and cellulose under a variety of conditions. The best catalyst, with a biomimetic double acid catalytic motif, can hydrolyze cellulose with one-fifth of the activity of commercial cellulases in aqueous buffer. As a highly cross-linked polymeric nanoparticle, the synthetic catalyst is stable at elevated temperatures in both aqueous and nonaqueous solvents. In a polar aprotic solvent/ionic liquid mixture, it hydrolyzes cellulose several times faster than commercial cellulases in aqueous buffer. When deposited on magnetic nanoparticles, it retains 75% of its activity after 10 cycles of usage.