In this study, the structural factors controlling the enzymatic saccharification of rice straw cellulose were examined by preparing structure-modified rice straw samples such as dewaxed, alkali-treated, oxidized, and swollen rice straw. It was found that the initial enzymatic saccharification rate of the various structure-modified samples was largely controlled by the initial cellulose surface area of the cellulose unit. Although the presence of lignin limited the cellulose surface area, there was no strong relationship between the lignin content and the initial reaction. On the other hand, the long-term enzymatic saccharification of rice straw cellulose highly depended on the lignin removal rate (lignin content). It was also found that silica is not a crucial factor in controlling the enzymatic saccharification. (C) 2014 Elsevier Ltd. All rights reserved.