To fully exploit the benefits of N-methylmorpholine-N-oxide (NMMO) in lignocelluloses bioconversion, a compatible system was established for efficient in situ saccharification of cellulose in NMMO-aqueous media in which the NMMO is able to activate and solubilize the cellulose, and the cellulases possess high stability and activity. Cellulase retained its original activity after being pre-incubated in 15% and 20% (w/v) NMMO solutions. After optimization of reaction parameters, high saccharification rate (96.5%) was obtained in aqueous-NMMO media by ultrasound assisted treatment of cellulose. The viscosity and FTIR analysis revealed that NMMO-treated cellulose under ultrasonic condition was porous and amorphous, which led to improved saccharification. The addition of trifle lignin in lower concentration improved the saccharification efficiency of sugarcane bagasse, while higher concentration interferes with hydrolysis. In conclusion, these findings provided great implications to develop a continuous process NMMO-cellulases system for transformation of native biomass. (C) 2011 Elsevier Ltd. All rights reserved.