Pretreatment and fractionation of lignocellulosics in biphasic system and moderate severity

The fractionation of macro-constituents is of paramount importance to efficiently exploit the biomass. The chemical and physical properties of cellulose, hemicellulose and lignin are different, but their separation is hindered by the co-penetration at microscopic level and by the chemical bonds among them. Several pretreatment have been proposed in order to disrupt such a complex structure making more efficient the action of solvents (aqueous or organic) and enzymes. The recovery yield and the purity of the obtained streams are an issue of all these process. Another issue is the digestibility of the residual cellulose that is the major source of glucose to feed subsequent fermentation processes. In this work we investigated the pretreatment of corn stover in a biphasic system constituted by a furanic solvent (2-MTHF) and oxalic acid solution. The pretreatments were carried out in a 200 mL Parr reactor under pressure of 10 bar of CO₂ at total solid concentration of 10 wt% and temperature range 130-150 °C.  The washed residue has undergone enzymatic hydrolysis tests with commercial mix in shaken flasks at 45°C up to 96h. The purity and recovery of C5, C6 sugars (monomers and oligomers) and lignin after pretreatment and digestion were assessed by FTIR, TGA and HPIC and reported to the initial content in the raw biomass.