High yield solvent extraction of hydrothermal and ball-milling treated lignin prior to enzymatic hydrolysis for co-valorization of lignin and cellulose in Miscanthus sacchariflorus

Abstract A lignin extraction procedure was developed for improving extraction yield, mitigating structural changes, and retaining depolymerization performance of the lignin fraction from hydrothermal and ball-milling treated miscanthus. The remaining residues after the lignin extraction process were subjected to enzymatic hydrolysis for evaluating the possibility of producing fermentable sugars. The extraction yield was improved by a factor of 5 due to hydrothermal treatment, and its extract contained approximately 50 g/L of total phenolic compound. The high molecular weight lignin fraction (Mw: 5640–6850 Daltons) was highly dissolved in 80% and 96% dioxane solution, but the low molecular weight part (Mw: 4170–5270 Daltons) was detected regardless of conditions. The major depolymerization products of HML are 4-vinylphenol (6.6 mg/g) and 2-methoxy-4-vinylphenol (4.3 mg/g). 90% of glucose yield was obtained after enzymatic hydrolysis of the extraction residue. Overall, both yields of lignin extraction and enzymatic hydrolysis of residue were improved by combining hydrothermal and ball-milling treatment and changing the solvent combination.