| This thesis includes three parts: 1.) effect of hydrogen peroxide on delignification of peat; 2.) pre-treatment of pine sawdust using various methods, including organosolv extraction, ultrasonic treatment, and sodium hydroxide treatment; and 3.) enzymatic hydrolysis of pre-treated pine sawdust for glucose production. The delignification efficiency (DE), pre-treatment efficiency (PE), and glucose yield, total sugar yield, and total weight loss were systematically quantified under different conditions. Effects of pre-treatments on peat and pine sawdust structure were characterized using various analytical tools, such as scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV spectrometer. The detailed results are summarized below: 1.) Pretreatment of peat with hydrogen peroxide under alkaline condition was studied for delignification in a batch reactor. Impact of reaction time, reaction temperature, and the concentration of hydrogen peroxide on lignin removal was systematically studied. Peat samples before and after pretreatment were characterized using FTIR. The hydrolyzate solution was characterized using UV-spectrometer. The delignification efficiency increased with an increase in reaction time and hydrogen peroxide concentration. There was an optimal reaction temperature (45°C) for delignification. The experimental results suggested that the optimal reaction condition is 1.5 wt% H2O 2, pH 11.5, temperature 45 °C, reaction time 12 h and about 40 wt% biomass can be dissolved under optimal conditions. The results indicated that the hydrogen peroxide pretreatment had significant effects on delignification of peat; however, the pretreatment could not change the lignin's structure. 2.) Pretreatment efficiency (PE) and delignification efficiency (DE) of pine samples with different pretreatment methods were studied, and SEM, FTIR, XRD analysis methods were used to examine the structural changes before and after the pretreatment. All the pretreatment methods, in particular the organosolv extraction, resulted in removal of lignin and hemicellulose. The PE and DE were 51.40%+/-2% and 76.5%+/-3% for organosolv extracted pine; 53.3%+/-1% and 77.20%+/-2.6% for organosolv extracted +ultrasound treated pine; 57.7%+/-1.1% and 81.5%+/-3% for organosolv extracted +NaOH treated pine; 61.6%+/-1% and 86.4%+/-3% for organosolv extracted+ultrasound+NaOH treated pine, respectively. Among all the methods tested, organosolv+ultrasound+NaOH achieved the highest pretreatment and delignification efficiencies of 61.6%+/-1% and 86.4%+/-3%, respectively, implying that the combination of these three methods did have a significant effect on removal of lignin and dissolution of hemicellulose. Through the observations from SEM figures, FTIR and XRD spectrums, the structural feature changes of the components in cell wall after the pre-treatment were clearly demonstrated: first, the cell wall was disordered, twisted and exposed its inner structure; second, the characteristic function groups in lignin and hemicellulose were removed or reformed; third, the pretreatment did not result in the structure change of cellulose but increased its content, as expected. 3.) Enzymatic hydrolysis of pine samples treated with different pretreatment methods was systematically studied. Different glucose yields, total sugar yields and total weight loss were obtained under various enzyme loading (0∼15.56 FPU cellulase) and reaction time (48 hours). The maximum glucose yield and the maximum total sugar yield were 5.78% and 7.13%, for raw pine, 9.56% and 30.14% for organosolv extracted pine, 10.74% and 24.07% for organosolv extracted + ultrasound treated pine, 13.64% and 26.81% for organosolv extracted and NaOH treated pine, and 19.27% and 22.40% for organosolv extracted + ultrasound + NaOH treated pine, respectively. It was observed that the glucose yields were positively proportional to the values of PE and DE from the pretreatment, while the total sugar yields were inversely proportional to the values of PE and DE. Compared to that of the untreated pine sawdust sample, hydrolysis of the pretreated pine samples led to 2-3 fold increases in the glucose and total sugar yields under the optimal conditions. These results suggest that enzymatic hydrolysis of softwood sawdust could be greatly enhanced by pretreatment of the feedstock by organosolv extraction combined with ultrasound and alkaline treatment. |
