Pretreatment of sugarcane bagasse using supercritical carbon dioxide combined with ultrasound to improve the enzymatic hydrolysis

► High efficiency of cellulose hydrolysis after treatment. ► No use of toxic reagents during the pretreatment. ► Low water consumption during the pretreatment. ► Low temperature in the pretreatment. This work evaluates the pretreatment of sugarcane bagasse combining supercritical carbon dioxide (SC-CO2) and ultrasound to enhance the enzymatic hydrolysis of pretreated bagasse. In a first step the influence of process variables on the SC-CO2 pretreatment to enhance the enzymatic hydrolysis was evaluated by mean of a Plackett–Burmann design. Then, the sequential treatment combining ultrasound+SC-CO2 was evaluated. Results show that treatment using SC-CO2 increased the amount of fermentable sugar obtained of about 280% compared with the non-treated bagasse, leading to a hydrolysis efficiency (based on the amount of cellulose) as high as 74.2%. Combining ultrasound+SC-CO2 treatment increased about 16% the amount of fermentable sugar obtained by enzymatic hydrolysis in comparison with the treatment using only ultrasound. From the results presented in this work it can be concluded that the combined ultrasound+SC-CO2 treatment is an efficient and promising alternative to carry out the pretreatment of lignocellulosic feedstock at relatively low temperatures without the use of hazardous solvents.