Effect of Sodium Hydroxide Pretreatment on Rice Straw Composition

Background/Objectives: Sodium hydroxide (NaOH) pretreatmentwas used to determine the effect of pretreatment on chemical composition of pretreated rice straw. The experiment was designed to measure the effects in terms of NaOH concentration and pretreatment time mainly on the total carbohydrate content (TOC) and lignin content of pretreated rice straw. Methods/Statistical Analysis:Compositional characterization was performed based on the National Renewable Energy Laboratory (NREL) laboratory analysis protocols. Rice straw obtained from Sekinchan, Selangor Malaysia was dried to reduce the moisture content (<15%) and ground to 2 mm particle size. Rice straw was pretreated with different concentration of NaOH (2%w/v, 6%w/v and 12%w/v) and pretreatment time of 1 and 3 hours, while temperature was kept constant at 55°C. Findings:Rice straw sample pretreated with 12%w/v NaOH for 1 hour gave the highest glucan content, an increase of 85.6% from the native untreated rice straw. This condition also yielded the best delignification effect which reduced the lignin composition up to 79.6%, while sample pretreated with 2%w/v for 3 hours gave the highest composition on total carbohydrate content of 79.16% for which included glucan, xylan and arabinan.Hence, the pretreatment condition of 2%w/v NaOH concentration for 3 hours was the best condition in order to obtain high total carbohydrate content while severe pretreatment condition of 12%w/v NaOH concentration for 1 hours was best to give the delignification effect to the rice straw. Application/Improvements: The results from this work can be used for further evaluation of pretreated rice straw using NAOH particularly for enzymatic hydrolysis. Is useful in determining the carbohydrate conversion during the hydrolysis.