In order to establish the correlation between hemicelluloses removal and bioconversion efficiency of cellulose, fractionation process with increasing NaOH concentration selectively released the hemicellulosic polymers with increasing molecular weight and decreasing degree of substitution. Not only the initial hydrolysis rates also the concentrations of glucose and ethanol were significantly enhanced from 5.93 and 8.39 g/L to the range of 8.67-9.60 g/L and 11.53-13.71 g/L after alkaline treatment, respectively. However, the maximum conversions of cellulose to glucose (61.9%) and ethanol (64.6%) were achieved as 33.0% hemicelluloses was still remained. Excluding the negligible effect on the crystal transformation of cellulose, the improvement of bioconversion efficiency was resulted from the synergetical effects of surface exposure, multi-layers collapse and the hydrophilic property of the cellulosic substrate. It is critical task to balance these factors by the partial removal of hemicellulosic component, not complete. (C) 2013 Elsevier Ltd. All rights reserved.