Two-stage acid hydrolysis was conducted on easy reacting cellulose and resistant reacting cellulose of fractionated Gelidium amansii (f-GA). Acid hydrolysis of f-GA was performed at between 170 and 200 degrees C for a period of 0-5 min, and an acid concentration of 2-5% (w/v, H(2)SO(4)) to determine the optimal conditions for acid hydrolysis. In the first stage of the acid hydrolysis, an optimum glucose yield of 33.7% was obtained at a reaction temperature of 190 degrees C, an acid concentration of 3.0%, and a reaction time of 3 min. In the second stage, a glucose yield of 34.2%, on the basis the amount of residual cellulose from the f-GA, was obtained at a temperature of 190 degrees C, a sulfuric acid concentration of 4.0%, and a reaction time 3.7 min. Finally, 68.58% of the cellulose derived from f-GA was converted into glucose through two-stage acid saccharification under aforementioned conditions. (C) 2011 Elsevier Ltd. All rights reserved.