Green and efficient conversion strategy of Eucalyptus based on mechanochemical pretreatment

Herein, the mechanochemical process combined diluted acid impregnation and ball-milling treatment was developed to overcome the recalcitrance of lignocellulose. The high-yield fermentable sugars (glucose and xylose) and impregnated enzymatic lignin (IEL) streams have been simultaneously obtained via mechanochemistry and enzymatic hydrolysis process. It was found that the mechanochemical pretreatment significantly facilitated the enzymatic hydrolysis of the treated substrates, releasing high yield (>90%) of fermentable sugars for further utilization. CP/MAS 13C NMR and solution-state 2D NMR techniques showed that the crystallinity index (CrI) and degree of polymerization (DP) of cellulose in the treated substrates were both decreased. In addition, detailed structural characterizations of the obtained IEL fractions were achieved by the state-of-the-art NMR and GPC techniques. Results showed that the IEL fractions presented similar structural features as compared to the corresponding native lignin (DEL). The study provides an efficient and clean pathway for the conversion of energy from lignocelluloses; meanwhile, the residual lignin with unchanged structures could serve as ideal feedstock for the liquid fuel, bio-based materials, and chemicals in the current biorefinery process.