Insights into the role of chemical-assisted densification in structural deconstruction and enzymatic hydrolysis enhancement of corn stover

Densification facilitates the utilization of lignocellulosic biomass by overcoming its limitations of low density and associated processing costs. In this study, acid- and alkali-assisted pelletization of corn stover was performed to investigate the synergistic effects of chemicals and mechanical compression on the physicochemical properties of the pellets and their enzymatic hydrolysis. Results from confocal Raman microscopy revealed that densification caused significant rupture and collapse of plant cell walls. The combined effects of chemicals, pressure, and heat during pelletization reduce biomass particle size and effectively degrade its components. Pelletization also lowers the water absorption capacity of biomass, enabling enzymatic hydrolysis slurries to stay well-mixed at high solid loadings. Acid-assisted pelletization hydrolyzed hemicelluloses into xylose, oligoglucose, and xylooligosaccharides, whereas alkali-assisted pelletization primarily degraded lignin. Enzymatic hydrolysis of pellets without further pretreatment demonstrated that H2SO4-treated pellets achieved glucose and xylose yields of 48.2 % and 72.8 %, respectively, while NaOH-treated pellets yielded 76.8 % glucose and 63.8 % xylose. These findings could facilitate the application of acid- and alkali-assisted biomass pelletization in large-scale biorefineries.