Selective extraction of high-viscosity hemicellulose from oil-tea camellia fruit shells using a choline...

Oil-tea camellia fruit shells (CFS) are an abundant but underutilized by-product, rich in hemicelluloses and promising for high-value-added applications. Deep eutectic solvents (DESs) are widely used in lignocellulosic biomass fractionation, but few studies focus on selective hemicellulose extraction-especially improving extraction efficiency and selectivity of hemicelluloses. This study applies the choline chloride/monoethanolamine DES system to CFS hemicellulose extraction. Under optimal conditions (0 mol% water, 80 °C, molar ratio 1:6, solid-to-liquid ratio 1:20), selective extraction was achieved: the extracted hemicellulose-rich fraction had a yield up to 15.62% with a hemicellulose content up to 81.51% and a lignin content down to 16.45%. Structural analyses confirmed that the extracted hemicelluloses retained a well-preserved β-(1 → 4)-d-xylopyranosyl backbone with l-arabinose and 4-O-methyl-d-glucuronic acid side chains. Compared to conventional methods (e.g., alkaline extraction, DMSO extraction), the extracted CFS hemicellulose-rich fraction exhibited a much higher viscosity (up to 3500 mPa·s at a shear rate of 0.1 s^-1 and 570 mPa·s at 1 s^-1), which reflects enhanced cohesive forces and adhesive performance and thus strengthens its potential for bio-adhesive applications. This work provides a pathway for efficient and green CFS hemicellulose extraction and advances high-value CFS biomass utilizations.