Acid hydrolysis of cellulose using hydrothermal reaction was conducted to maximize reducing sugar concentration and the response surface methodology (RSM) was applied to study the effects of independent variables, such as reaction temperature (116 ~ 184oC), reaction time (12 ~ 28 min) and hydrochloric acid concentration (HCl, 0.0159 ~ 0.1841 N) on reducing sugar concentration and production yield from the cellulose. With the optimum conditions of the acid-catalyzed hydrothermal hydrolysis, the reducing sugar (RS) was obtained as 369.14 mg-RS/g-cellulose in 172.77oC of the reaction temperature, 28.41 min of the reaction time and 0.067 N of the hydrochloric acid concentration. The glucose (Glu) was obtained as 281.94 mg-Glu/g-cellulose in 154.70oC of the reaction temperature, 11.59 min of the reaction time and 0.184 N of the hydrochloric acid concentration.

Sugar, starch and lignocellulosic biomass has been mainly used as raw materials for the production of the bioethanol. However, the sharp fluctuation of grain prices, a threat of world famine, and hardly biodegradable substance like lignin contained in lignocellulosic materials make the pre-processing of the biomass complicated in several aspects. As a result, the focus of attention has now shifted to the ‘third biomass’ such as algae, which has a high value of energy recovery. In this study, a kind of macroalgae and its characteristic were surveyed and then, the physical, biological, chemical, combined, and hydrothermal pretreatments for its hydrolysis were deeply considered. Consequently, the macroalgae could be more effectively hydrolyzed at the combined process such as the hydrothermal-chemical or biological treatment, chemical-biological treatment and so on than the single process like the biological pretreatment.