Mechanoenzymatic hydrolysis of cotton to cellulose nanocrystals†

Solid-state mechanoenzymatic approaches for the production of cellulose nanocrystals from cotton were examined using three commercially available cellulase systems from Trichoderma reesei, Aspergillus niger and a Cellic CTec2 cellulase blend. A rapid and sharp drop in the degree of polymerization, together with the proportional increase in cellulose crystallinity and generation of nanoscale particles, indicates that cotton is extensively transformed to cellulose nanocrystals with just 15 minutes of ball milling of cotton in the presence of the cellulase enzymes. Subsequent aging of the solid reaction mixture at 55 °C did not significantly affect the degree of polymerization, but resulted in higher material losses due to the increased production of glucose. These results reveal that the endo-activity of the commercial cellulase preparations on cellulose is particularly efficient in solid reaction mixtures (solid loading 50 wt%), allowing for a rapid acid-free generation of cellulose nanocrystals with as low as 0.085 wt% enzyme loading.