After 48 h, the solution was filtrated through a G5 sintered glass filter to remove unreacted cellulose. The filtrate was concentrated in a rotary evaporator under reduced pressure at 50 °C. The product was purified on a silica gel column (silica gel 60N, 63–210 µm, 60 g, 18 cm × 3.2 cm) with ethyl acetate/2-propanol/water (16:3:1, v/v/v) to give methyl β-D-glucoside (397 mg, 33%). The preparative-scale synthesis was repeated twice.
The 1H nuclear magnetic resonance (NMR) spectrum of methyl β-D-glucoside was recorded on a Bruker AVANCE II 400 FT-NMR (400 MHz) spectrometer. 1H NMR (D2O) δ 3.04 (1H, dd, J = 8.0, 9.2 Hz, H-2), 3.16 (1H, t, J = 9.2 Hz, H-4), 3.22–3.27 (1H, m, H-5), 3.27 (1H, t, J = 9.2 Hz, H-3), 3.36 (3H, s, OCH3), 3.51 (1H, dd, J = 5.9, 12.3 Hz, H-6b), 3.71 (1H, dd, J = 2.2, 12.3 Hz, H-6a), 4.16 (1H, d, J = 8.0 Hz, H-1).
Quantification of methyl β-D-glucoside and cellobiose by HPLC
Methyl β-D-glucoside and cellobiose were monitored by HPLC same as chapter II.
The retention times were 6.37 min (±0.31%), and 12.39 min (±0.29%), respectively.
Their yields were determined by the following equation:
Yglucoside (%) = (Cglucoside×162/194)/Ccell×100%, Ycellobiose (%) = (Ccellobiose×162/171)/Ccell×100%,
where Yglucoside and Ycellobiose are the yields of methyl β-D-glucoside and cellobiose, The Cglucoside, Ccell, and Ccellobiose are the concentrations of methyl β-D-glucoside, cellulose and cellobiose respectively, in mg/mL.
CONCLUSIONS
Cellulose was pretreated by IL/cosolvent and then enzymatic convert to glucose and methyl β-D-glucoside in this study.
CHAPTER I
All of the cosolvents tested in this investigation, including pyridine, NMI, DMF, DMAc, DMI, NMP, and DMSO, effectively decreased dissolution temperatures of crystalline cellulose to 30 °C in [Amim]Cl. Moreover, increased proportions of [Amim]Cl in the mixed solvent systems contributed to solubilization efficiency, and the solubility of microcrystalline cellulose reached 12–15% at 30 °C in [Amim]Cl/NMI, [Amim]Cl/NMP and [Amim]Cl/DMSO at 1.5 g/0.5 g. TGA shows that thermal stability of the regenerated cellulose from [Amim]Cl/DMSO is significantly higher than that without DMSO. In case of filter paper pulp, NMI, NMP, and DMSO effectively decrease the dissolution temperature, as well. Significant decrease in DP was observed for NMI and NMP, but not for DMSO. Finally, [Emim]OAc/DMAc dissolved 12%
filter paper pulp at 30 °C without DP decrement, whereas [Emim]OAc dissolved only 5–8% pulp at 30 °C and led to 8–9% decrease in DP. In conclusion, some cosolvents including DMSO and DMAc increase solubilization efficiency and have superior cellulose-protective effects during enhanced dissolution of cellulose in ILs.
particular, a novel AAIL, [TBP][DMGly], was the most effective in the presence of DMSO leading to nearly 100% conversion of cellulose to glucose. The biocompatibility of [TBP][DMGly] with cellulase was higher than that in the case of the other ILs. In this system, it was possible to dissolve and hydrolyze cellulose in one batch process. The ratio of [TBP][Gly] to DMSO greatly affects the dissolution efficiency and enzymatic hydrolysis of cellulose and this ratio can be easily adjusted according to the requirements.
CHAPTER III
Pretreatments with AAIL/cosolvent were essential for the enzymatic synthesis of methyl β-D-glucoside from cellulose, and the initial formation rates and yields increased dramatically. The methanol content was one of the key factors for the effective synthesis, because methanol is not only an important reactant but also has an inhibitory effect on cellulase activity. Exploration of the formation route provides valuable insights into the highly efficient synthesis of methyl β-D-glucoside from cellulose.
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ACKNOWLEDGEMENTS
First and foremost I want to thank my supervisor Professor Noriyuki Nakajima and Associate Professor Takao Kishimoto. Their brilliant and timely guidance made my doctoral research work carried out smoothly. I have appreciated Lectuer Masahiro Hamada for his help during the experiments. I am especially grateful for members of our research group, and all of them are friendly and warmhearted to make me have a perfect life in Japan. I am also thankful for the financial support from Toyama Prefectural University and our research office to make me concentrate on the study.
Finally I want to thank my family for their love and understanding of my choice for studying abroad.