Rapid Depolymerization of Decrystallized Cellulose to Soluble Products via Ethanolysis under Mild Conditions

Efficient cellulose depolymerization is a major bottleneck for economical production of second-generation biofuels. In this work, crystalline cellulose was subjected to sequential ball milling and ethanolysis as a mild and selective depolymerization approach. Ball milling and ethanolysis resulted in 38±1 % cellulose conversion, with 24 % ethyl-glucopyranoside as the main identified and quantified product and negligible side reaction of the ethanol solvent to form diethyl ether. In comparison, ethanolysis of the original cellulose resulted in only 3±1 % conversion. Additional soluble products from cellulose ethanolysis included carbohydrate isomers and oligomers, differing from the products obtained from hydrolysis. X-ray diffraction and nuclear magnetic resonance spectroscopy revealed increased crystallinity post-reaction, retarding further depolymerization. Hot liquid water extracted soluble oligomers from the ethanolyzed cellulose, suggesting formation of a nanoscale barrier of crystalline cellulose that traps soluble products during ethanolysis. Use of cellulose-swelling co-solvents and repeated mechanical decrystallization both proved effective at increasing cellulose conversion and soluble product yields. Repeated ball milling and ethanolysis resulted in 62±1 % cellulose conversion. Ethanolysis of decrystallized cellulose has potential for rapid (<2 h) de-polymerization at mild conditions.

Immobilization of Cellulase on Magnetic Nanocarriers

The constant increase in the number of sustainable products on the global markets demands new biotechnological processing strategies such as the purification and recovery of biocatalysts. Superparamagnetic iron oxide nanoparticles exhibit excellent recovery properties as carrier materials in enzyme catalysis. We present the simple and fast electrostatic assembly of cellulase (CEL) and low-priced silica-coated magnetic nanoparticles, which demonstrates stable enzyme bonding and excellent colloidal stability. The high CEL loading (0.43 g g-1), without leaching of biocatalyst and high recovery yields (75 %), could be sustained over ten magnetic recycling steps. The highlight of this study is the preservation of a high enzymatic activity and, therefore, the outstandingly high lifecycle stability.