Depolymerization of Lignin from Extracted Solid Waste of Cupressus lusitanica Mill. Biomass Using Imidazole

Abstract

Implementation of green chemistry and biorefinery concept are needed to boost production of biomass-derived fuels, chemicals, and materials with cost-effective processing of sustainable feedstock. The use of imidazole as a novel solvent for biomass pretreatment creates an approach that helps accomplish this concept. The present work is dedicated to study the pretreatment of residual lignocellulosic biomass, namely, extracted solid waste of Cupressus lusitanica, by application of the alkaline solvent—imidazole. The pretreatment allowed obtaining cellulose- and hemicellulose-rich fractions, whereas lignin was depolymerized. Both cellulose and hemicellulose recovery were highly dependent on the reaction conditions. The highest cellulose content was obtained at 160 °C for 4 h and was 40.7 ± 0.6 wt% with a delignification yield of 65.2 ± 0.4 wt%. The effect of biomass delignification on the efficiency of enzymatic digestibility was also analyzed and it was observed a good linear relationship between the delignification yield and the glucan to glucose yield. The presence of added-value phenolic compounds from depolymerized lignin in recovered imidazole was analyzed by capillary electrophoresis and determination of total phenolic content and antioxidant activity was also performed. These compounds were tentatively identified and their structures proposed on the basis of the HPLC–MS analyzes.