Magnetic Bifunctional Ru-Enzyme Catalyst Allows for Sustainable Conversion of Cellulose Derivative to D-Sorbitol

Here, we report the development of a novel bifunctional nanobiocatalyst for a one-pot cascade transformation of carboxymethyl cellulose (CMC) to D-sorbitol. The nanobiocatalyst is based on magnetic nanoparticle aggregates (MNAs) functionalized with chitosan (CS) cross-linked by tripolyphosphate (TPP). It contains two types of catalytic sites: cellulase (Cel, 5 wt.%) and Ru (3 wt.%) nanoparticles (NPs) of 0.7 nm in diameter. To optimize the nanobiocatalyst structure and composition, we first synthesized the biocatalyst, MNA-CSP-Cel (CSP stands for the CS layer cross-linked by TPP), as well as the nanocatalyst, MNA-CSP-Ru, and studied them in the one-step reactions of hydrolysis and hydrogenation, respectively. The data obtained allowed us to optimize the composition and properties of the bifunctional nanobiocatalyst, MNA-CSP-Ru-Cel, and to choose the best reaction conditions for the cascade process. MNA-CSP-Ru-Cel was characterized using transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and porosity measurements. The knowledge obtained enabled us to perform a cascade transformation of CMC to D-sorbitol with a yield of 83.2% for 10 h at 70 °C and a hydrogen pressure of 4 MPa. The yield demonstrated in this work is much higher than that reported to date for the same cascade process.