Acid-assisted organosolv pre-treatment and enzymatic hydrolysis of Cynara cardunculus for the production of glucose

Lignocellulosic biomass is non-edible feedstock that can be used into integrated biorefinery for the production of biochemicals and biofuel. Among lignocellulosic biomass, cardoon (Cynara cardunculus) is a promising crop thanks to its low water and fertilizer demand. Organosolv is a chemical treatment that uses numerous organic or aqueous solvent mixtures and a small amount of acid catalyst in order to solubilize the lignin and hemicellulose fractions, making the cellulose accessible to hydrolytic enzymes. In this work, lignocellulosic residues of cardoon underwent a two-step treatment process to obtain fermentable glucose. In the first step the milled biomass was subjected to microwave assisted extraction (MAE) using an acidified water/γ-valerolactone mixture yielding a solid cellulose pulp. In the second step, the cellulose pulp was hydrolyzed by cellulolytic enzymes into glucose. The first step optimization was carried out by means of backward elimination of not statistically significant factors performed on a full factorial design of experiment (DOE). The investigated factors were process temperature, acid catalyst concentration, and water/γ-valerolactone ratio. A glucose production equal to 30.17 grams per 100 grams of raw material (89% of the maximum theoretical yield) was achieved after conducting the process at 150 °C using an acidified water solution (1.96% H2SO4 w/w).