Optimization of lignin extraction by response surface methodology from sugarcane bagasse using deep eutectic solvents (DES)

Lignin removal in lignocellulosic biomass is an important step to obtain efficient fermentable sugars production during enzymatic hydrolysis. Likewise, interest has emerged in the past few years for the application of eco-friendly technology for biomass delignification. Thus, the use of deep eutectic solvents has been considered as an alternative to treat lignocellulosic biomass. The main objective of this work was to optimize the sugarcane bagasse delignification using deep eutectic solvents (DES): ChCl-Gly and ChCl-Urea. Previously, the effect of temperature (80–120 °C) and reaction time (2–6 h) were evaluated. Then, response surface methodology was used to optimize the conditions of reaction time, liquid-solid ratio (LSR), and temperature. The results found in this investigation showed that the increase of the reaction time and temperature improve the lignin removal. The optimization revealed that under optimal conditions it is possible to remove an 81.1% (13.12 h, LSR 23.4:1 and 160 °C) and 82% (14.04 h, LSR 17:1 y 160 °C) of the lignin in the sugarcane bagasse using ChCl-Gly and ChCl-Urea, respectively. Also, it is possible to convert 50–80% of the cellulose in sugarcane bagasse after the treatment with DES. This demonstrates that the use of DES is efficient and useful to remove the lignin from lignocellulosic biomass.