Dissolution and enzymatic hydrolysis of sugarcane bagasse using ionic liquids and deep eutectic solvents

Abstract

The recalcitrant nature of biomass hampers the enzymes' access to polysaccharides. Ionic liquids (ILs) and deep eutectic solvents (DESs) are eco-friendly solubilizing agents since these facilitate effective delignification and enhance carbohydrate's accessibility to enzymes for proficient bioconversion. This study focuses on the pretreatment of sugarcane bagasse with a series of choline-based ILs and DESs to enhance biomass hydrolysis and lignin extraction. Initially, a screening of the green solvents in the dissolution process was performed, where Choline chloride/acetic acid DES showed the best results for xylan (61.7 %) and Choline lactate IL for cellulose (53.4 %) and both with complete dissolution (100 %) for lignin. The results suggested that increased temperature and biomass/solvent ratio lead to higher dissolution yields, which achieved 80 % for most solvents studied. In contrast, the opposite is seen for water content. Pretreatment with the green solvents allowed for greater hydrolysis of the non-dissolved materials, with a 2–4-fold increase compared to untreated bagasse. Enzymatic hydrolysis with Cellic CTec2 showed high yields (above 85 %). Furthermore, remarkable results were obtained, where more than 80 % of the non-dissolved material pretreated with DES was hydrolyzed. The lower concentrations of enzymes led to better hydrolysis results for the material pretreated with DES (100 %) and the untreated material (60.8 %). A wide optimum range was observed for temperature and pH with temperatures from 30 to 60 °C and pH between 3 and 6. Overall, the results of this study provide an effective and facile pretreatment method for lignocellulosic biomass waste with green solvents to enhance enzymatic hydrolysis.