Fibrillation of wood cell walls into submicron and/or nanoscale fibers was successfully carried out in the presence of water by using a batch-type kneader with combination-available twin-screw elements. The results obtained are expected to be used for the application of a twin-screw extruder. Two types of screw combinations were used for applying different shearing and distribution forces. Most of the fibers of the fibrillated products had diameters less than 1 mu m, and some of them had diameters less than 100 nip. The maximum glucose yield by enzymatic saccharification Was found to be 54.2% in the fibrillated products kneaded for 20 min after ball milling for 20 min using a screw combination for applying high shearing force. The fibrillation increased the surface area of cellulose. The glucose yield was improved by cooking the fibrillated products with water at 135 degrees C under 0.25 MPa, revealing that only mechanical kneading appears to have some limitation to expose cellulose for complete enzymatic saccharification. (C) 2009 Elsevier Ltd. All rights reserved.