Furthermore, the silica layer prevents the accessibility of microorganisms to carbohydrates inside the straw (AgbaglaDohnani et al., 2003). Thus, removing the silica from rice straw canbe a proper strategy for increasing the accessible cellulose surface area to hydrolytic enzymes in the hydrolysis process. In this study, the effect of sodium carbonate pretreatment on the structure and silica content of rice straw and its consequence on hydrolysis and fermentation steps were studied.