Study On Enzymatic Hydrolysis Of Corn Stover Based On Sporl And Hot Water Pretreatment Process

Ethanol production from lignocellulosic materials has become an inevitable trend of new energy development. The pretreatment is one of the critical steps in the byconversion of lignocellulosic materials to ethanol, which would directly influence enzymatic hydrolysis efficiency of cellulose and cost of ethanol production. Therefore, it is necessary to develop new lignocellulose pretreatment process with high efficiency, low pollution and les investment.In the paper, both hot water and SPORL method were studied to pretreat corn stover by analysising dissolution rate of lignin, dissolution/retention rate of pentosan, cellulose conversion and glucose yield. In addition, two-stage pretreatment combined SPORL with hot water was studied too.Firstly, the influences of temperature, holding time and chemical additives on corn stover during hot water pretreatment were investigated. Alkyl phenol polyoxyethylene ether OP-10and inorganic salt FeCl3were studied as catalysis for the degradation of hemicellulose in corn stover. Results showed that the optimal conditions of hot water pretreatment were liquid ratio1:4, temperature170℃, holding time30min. Under such conditions, the appropriate dosages of OP-10and FeCl3are0.3%and6.5%, respectively. The dissolution rate of pentosan in liquid achieved52.47%when the corn stover was pretreated with9.75%(0.15M) FeCl3at140℃for30min, which was10-fold greater than pretreatment with hot water.Secondly, it has been seen from results that SPORL pretreatment can effectively improve the enzymatic hydrolysis of substrate. Sulfuric acid had negative effect on the concentration of furfural and5-HMF in liquid phase. The optimal conditions of SPORL pretreatment were the dose of sodium bisulfite5%, sulfuric acid1.84%, liquid ratio1:4, temperature180℃, holding time20min. Under these conditions, conversion rate of enzymatic hydrolysis is86.31%, glucose yield is80.71%at the dosage of cellulose10FPU/g and1.0CBU/g. Concentration of furfural and5-HMF was6.83g/L and2.25g/L in the liquid, respectively.Finally, the two-stage pretreatment, SPORL pretreatment after hot water, was used to improve fermentable sugars yield. Compared with single-stage hot water and SPORL, the two-stage pretreatment significantly improved the enzymatic hydrolysis of cellulose and glucose yield. When the hot water pretreatment (9.75%FeCl3,140℃and30min) combined with SPORL pretreatment (3%NaHSO3,170℃and30min.), the dissolution rates of pentosan be up to66.5%, the enzymatic hydrolysis rate of substrate and glucose yield were90.57%and71.29%, respectively.