The Characteristic Analysis Of Different Cellulose Substrates During The Steam Explosion Pretreatment And Enzymatic Hydrolysis Process

The substrate diversity of various cellulose substrates was the key factor for hindering the efficiency of pretreatment and enzymatic hydrolysis. In this study, the bacterial cellulose (BC), rice straw (RS) and Caragana korshinskii Kom. (CKK) were used as the representatives of pure cellulose, grass biomass and woody biomass. In order to study the relationships between the efficiency of pretreatment or enzymatic hydrolysis and the physicochemical characteristic of cellulose substrates, the effects of steam explosion pretreatment on recalcitrance of RS and CKK and the regularities of different types cellulose substrates during the enzymatic hydrolysis process were investigated. The adsorption capacity of different cellulose substrates to endoglucanase (EG) and exoglucanase (CBH I and CBH II) were also studied.The result indicated that steam explosion pretreatment (SEP) could effectively promote biomass degradation. The glucose yield of SEP-treated RS (SEPR) and SEP-treated CKK (SEPK) was up to 82.56% and 45.46% after 72 h enzymatic hydrolysis,which was 0.88 and 1.43 times higher than untreated RS (UR) and untreated CKK (UK).And the xylose yield was up to 43.14% to 37.03%,which was 2.25 and 3.38 times higher than UR and UK. SEM micrographs indicated that the compact physical structure of RS and CKK was destructed after steam explosion pretreatment and the effect of steam explosion to the physical structure of CKK was lower than that of RS.The glucose yield of BC was up to 93.12% after 72h enzymatic hydrolysis when the cellulose loading was 1%, which was higher than that of RS and CKK. For BC, the glucose yield was obviously decreased with increasing cellulose loading. The glucose yield was decreased to 55.34% when the cellulose loading was increased to 10%. After adding xylanase to 8mg protein /g cellulose, the yields of glucose and xylose of SEPR and SEPK were increased. However, after adding pectinase into 5 mg protein/g cellulose, the glucose yields of SEPR and SEPK were decreased to 69.25% and 42.22%. The ability to adsorb enzymes of RS and CKK was significantly enhanced after steam explosion pretreatment.The particle sizes of BC, SEPR and SEPK were reduced gradually during the enzymatic hydrolysis process from the result of SEM analysis. The FTIR analysis showed that the intensity of cellulose related characteristic peaks of BC and SEPR was decreased after enzymatic hydrolysis, but the intensity of lignin related characteristic peaks of SEPR and SEPK was increased. The CrI of the samples did not exhibit obvious change during the enzymatic hydrolysis process.The binding ability of endoglucanase (EG) to cellulose substrate was higher than that of exoglucanase (CBH ? and CBH ?) and the adsorption law of substrate to EG, CBH I and CBH ? was shown as a periodic adsorption mode.