Efficient Fractionation of Corn Stover for Biorefinery Using a Sustainable Pathway

Abstract

This study presents a sustainable pathway for fractionating corn stover to produce glucose, high-quality lignin nanoparticles (LNPs), and levulinic acid (LA) based on the use of p-toluenesulfonic acid (p-TsOH), a solvent having strong acidity and surface activity at a high concentration. At a moderate pretreatment temperature (100 °C), 85% of xylose, 88% of arabinose, and 83% of lignin were removed from the substrate and present in the hydrolysate, while the cellulose yield in the solid residue fraction was 93%. The cellulose fraction exhibited much reduced “biomass recalcitrance” and was readily enzyme-hydrolyzed, with its glucose yield reaching up to 93% at a high solid concentration of 15% (w/w). The hydrolysate, involving the p-TsOH catalyst, was recycled for further hydrolysis of fresh corn stover: after recycling the hydrolysate four times, the cellulose fraction still had a high glucose yield of 81%. The lignin fraction in the hydrolysate was utilized in the form of LNPs, which were prepared as a result of diluting the recycled hydrolysate. The as-prepared LNPs were spherical and uniform, with an average particle size of 147 nm. The application of LNPs in the preparation of chitosan film significantly improved its strength. After LNP preparation, the diluent containing monomeric sugars was directly heated to 180 °C to produce LA in the presence of p-TsOH (an effective catalyst) with an LA yield of 57.1%. The LA was easily separated from the spent acid based on methyl isobutyl ketone (MIBK) extraction, and the p-TsOH/water mixture was recycled in the process.