8-27: Co-production of cellulose nanocrystal and monosaccharides from disk milled biomass by enzymatic hydrolysis

This work addressed the coproduction of cellulose nanocrystal (CNs) and monosaccharides via the separate enzymatic hydrolysis of pure cellulose, Eucalyptus holocellulose, wood pulp and sugarcane bagasse which were previously fibrillated by disk milling. Nevertheless acidic hydrolysis has been reported for the production of CNs the use of endoglucanases, which have the ability to hydrolyze the amorphous cellulose regions, allows the advantageous adjustment of the aspect ratio of the cellulose nanocrystals. Enzymatic hydrolysis experiments (10 mg/mL substrate concentration) were conducted using the commercial enzyme Optimash^TMBG (Genencor International, USA) and thermophilic enzymes (endoglucanase from Pyrococcus horikoshii and β-glucosidase from Pyrococcus furiosus). The physical properties and morphology of fibrillated biomass and the residual saccharification product were analyzed by X-ray diffraction, the measurement of the specific surface area (SSA), Atomic Force Microscopy and Scanning Electron Microscopy. Disk milling treatment resulted on the formation of long and twisted nanofibers with 15–30 nm wide which changed into shorter and straighter microfibers, mixed with CNs, in the residue of the enzymatic hydrolysis. The aspect ratio of the cellulose fibers, which depended on the degree of the enzymatic hydrolysis, was successfully adjusted. Enzymatic saccharification resulted on the increase of SSA and crystallinity. Glucose concentrations varied within 1.0 - 7.4 mg/mL, depending on the enzyme and biomass type. The use of Optimash on holocellulose, sugarcane bagasse and pulp also allowed the detection of 0.36 to 1.65 mg/mL of xylose.