Supramolecular Regulation and Controllable Coproduction of Bamboo Nanocellulose and Mono/Oligosaccharides via Dual-Enzymatic Treatment Assisted by Ball Milling

Nanocellulose (NC) derived from lignocellulosic biomass has served as a promising material for functional applications. However, conventional chemical and mechanical processes for NC fabrication are environmentally harmful and energy intensive and may inevitably cause component loss. Herein, a green dual-enzymatic treatment assisted by ball milling strategy was proposed for bamboo pulp to produce NC with varied morphologies and supramolecular structures, as well as the coproduction of monosaccharides and xylooligosaccharides (XOS) with reduced enzyme loading and treatment time. Endoglucanase (EG) and xylanase at various loading ratios were used for adjusting the physical–chemical structures of NC. Mechanistic studies showed the accomplishment of nanofibrillation under shorter ball milling time via retention of hemicelluloses, while longer ball milling time intensified fibril deconstruction, thus exposing cellulose hydrophobic surfaces favorable for subsequent enzymatic hydrolysis. The method was subsequently applied to bamboo holocellulose and microcrystalline cellulose (MCC)/xylan models, which obtained the highest yields of 23.2% glucose, 24.4% XOS, and 21.5% NC. Bamboo holocellulose produced NC with a high aspect ratio of up to 55.1, while MCC produced spherical NC with cellulose II allomorph. The proposed ball-milling-assisted dual-enzymatic treatment can provide theoretical guidance for high-value conversion and more complete utilization of bamboo polysaccharides.