Comparison of Three Microwave/Chemical Pretreatment Processes for Enzymatic Hydrolysis of Rice Straw

The microwave/chemical Pretreatment is a more effective rice-straw Pretreatment technique than the conventional heating chemical Pretreatment by accelerating reactions during the Pretreatment process. In this paper, three microwave/chemical Pretreatment processes of rice straw, viz microwave/alkali, microwave/acid/alkali and microwave/acid/alkali/H2O2 were investigated for its enzymatic hydrolysis and the xylose recovery from the Pretreatment liquor. Firstly, the effect of three microwave/chemical Pretreatment processes of rice straw on its weight loss and chemical composition was examined. The results show that the rice straw pre-treated by microwave/acid/alkali/H2O2 had the highest weight loss and cellulose content. Then, the xylose recovery from Pretreatment liquor was studied. The xylose could not be recovered during the microwave/alkali Pretreatment process, but it could be recovered as crystalline xylose during the microwave/acid/alkali and microwave/acid/alkali/H2O2 Pretreatment processes. Finally, the enzymatic hydrolysis of pre-treated rice straw (substrate concentration 50 g l−1, pH 4·8 and enzyme loading 20 mg g−1 substrate) was also investigated and the results indicate that the rice straw pre-treated by microwave/acid/alkali/H2O2 had the highest hydrolysis rate and glucose content in the hydrolysate.