Study On The Pretreatment And Enzymatic Hydrolysis Of Corn Stover Enhanced By Ultrasound And Additives

Cellulose and hemicellulose were the major components of plant materials, and they could be converted to sugar by chemical, physical and biological methods such as sulfuric acid hydrolysis or enzymatic hydrolysis. In this study, ultrasound, BSA (Bovine Serum Albumin) and Tween were used in order to reduce the quantity of sulfuric acid and enzyme, meanwhile, the conversion rates were also improved. The main results were shown as follows:1. There were some effects on the conversion of materials. The ultrasound time and power were the most important factors including the temperature, concentration and pretreatment time. First, the conversion rate at 121℃without ultrasound was equivalent to the rate at 110℃with ultrasound; Second, when the acid concentration was 0.50%, the rates of pretreatment and enzymatic hydrolysis were 34.2% and 31.8%, which were higher than the rates 32.0% and 26.7% when acid concentration was 0.75%; Third, when the pretreatment time was 1.5h, the conversion rate was 32.5%, which was 10.9% higher than that without ultrasound.2. From the HPLC analysis of the pretreatment liquid with ultrasound and without ultrasound, it was found that at lower temperature there were no HMF (5-hydroxymethyfurfural) and furfural. After ultrasound radiation the quantity of glucose and xylose were not reduced, but acetic acid was decreased.3. The enzymatic hydrolysis rate was increased with the BSA concentration. BSA was adsorbed on the lignin earlier, so available enzyme was increased. When the BSA concentration was 0.5g/L, the hydrolysis rate was 32.8% which was 25.2% higher than that without BSA.4. Tween has better effect on the enzymatic hydrolysis. Without Tween the conversion rate was 26.2%. After adding Tween 20 and Tween 80 the rates were increased to 34.4% and 37.0%. As the HPLC analysis showed, the glucose concentration was improved to 6.00 g/L and 6.08g/L, increased by 26.1% and 27.7%. The xylose was increased by 63.8% and 66.0%. Cellobiose was increased by 22.7%.5. With the increase of ultrasound power the kinetic parameters were also increased. Vm and Km were 3.59g/L*h and 25.14 without ultrasound and 12.48g/L*h and 85.51 with ultrasound, respectively. 6. From the FTIR analysis it was found that the wave crests were much sharper at 1514cm-1, 1604cm^-1 and 897cm^-1.This showed that the vibration of C-O andβ-bonds were strengthened.