Development of sustainable sugarcane bagasse biorefinery using a greener deep eutectic solvent from hemicellulose-derived acids

Acid-based deep eutectic solvents (ADES) have recently been tested as an emerging technology in biomass deconstruction. In particular, the use of hemicellulose-derived carboxylic acids has attracted great interest as this type of ADES can enable a sustainable closed-loop biorefinery, due to their efficiency and recyclability. Therefore, this study proposed the pretreatment of sugarcane bagasse (SCB) with acetic acid, as a biomass-derived chemical, and choline chloride [ChCl]:AA to perform a complete biomass fractionation to enhance enzymatic digestibility. Thus, this work analyzed the effect of different temperatures and reaction time during pretreatment, studying the impact on biomass composition and digestibility during enzymatic hydrolysis. In addition, the reuse of ADES to produce an environmentally friendly and low-cost SCB biorefinery was explored by studying the physicochemical modifications in polysaccharide-rich material (PRM) and lignin-rich material (LRM) by ATRFTIR and SEM photography. Furthermore, the ADES content was also characterized by HPLC after each recycling cycle. The results demonstrated efficient polysaccharide conversion, promoting an enrichment in glucan (>60%) and xylan (>20%) content under mild operating conditions (130 degrees C and 90 min) supported by ATR-FTIR and SEM. Furthermore, SCB pretreated under these selected conditions achieved higher digestibility, increasing by 89% for glucan and 73% for xylan, using a simple and competitive process. In contrast, increasing the temperature above 130 degrees C did not improve the enzymatic digestibility of SCB. Thus, ChCl:AA could be recycled and reused. Therefore, this study demonstrated the potential of AA in DES pretreatments as an environmentally friendly and efficient method for the valorization of SCB components.