Enzyme-assisted production of cellulose nanofibers from bleached and bleached/sulfonated sugarcane bagasse: impact of sulfonation on nanocellulose properties and yields

Partial enzymatic hydrolysis is a green alternative to chemical processes to facilitate the isolation of cellulose nanofibers (CNFs). In this work, we compared the production of CNFs from two sugarcane bagasse substrates (bleached and bleached-sulfonated) using partial enzymatic hydrolysis with the commercial cocktail Cellic CTec3®, followed by ultrasonication. The effect of pretreatments and enzyme dosage on CNF properties and yields were evaluated. Mild enzymatic hydrolysis applied to sulfonated samples using only 0.312 mg enzyme/g substrate for 6 h increased CNF yield up to 2.5-fold and resulted in micrometer length fibers with an average diameter between 5 and 6 nm, as demonstrated by detailed morphological characterization of the substrates. These results were achieved due to the combination of the delignification steps and sulfonation, which enhanced enzymatic hydrolysis and fibrillation efficiency. Furthermore, combining enzymatic hydrolysis and sulfonation increased the CNF thermal stability (56–111 °C for bleached and 87–97 °C for bleached and sulfonated samples). These results demonstrated a pivotal role of enzymes in green CNF production and revealed the optimized hydrolysis/pretreatment conditions for manufacturing CNFs with advanced properties using enzymatic mixtures.