| 1. |
Masaki Okamoto, Takahiro Sakatsume, Shuntaro Tsubaki, Yuji Wada, Interlayer-expanded MWW-type zeolite catalysts with carbon filler in expanded micropores for efficient microwave heating, Journal of Materials Chemistry A, 10.1039/D2TA01602H, 10, 14585-14593, 2022.06. |
| 2. |
Tsubaki, Shuntaro; Matsuzawa, Tomoki; Higuchi, Tomoki; Fujii, Satoshi; Wada, Yuji, Determining the influence of microwave-induced thermal unevenness on vanadium oxide catalyst particles, Chemical Engineering Journal, 10.1016/j.cej.2021.133603, 433, 2, 133603, 2022.04. |
| 3. |
Matsuhisa, Masayuki; Kishimoto, Fuminao; Furusawa, Kosuke; Tsubaki, Shuntaro; Wada, Yuji, Microwave Boosting of Interfacial Tunneling Electron Transfer in a Quantum Dot-Sensitized Photoelectrode, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 10.1246/bcsj.20210401, 95, 2, 288-295, 2022.02. |
| 4. |
Tsubaki, Shuntaro; Nakasako, Yuki; Ohara, Noriko; Nishioka, Masateru; Fujii, Satoshi; Wada, Yuji, Ultra-fast pyrolysis of lignocellulose using highly tuned microwaves: synergistic effect of a cylindrical cavity resonator and a frequency-auto-tracking solid-state microwave generator, GREEN CHEMISTRY, 10.1039/c9gc02745a, 22, 2, 342-351, 2020.01. |
| 5. |
Sanchez, Pablo B.; Tsubaki, Shuntaro; Padua, Agilio A. H.; Wada, Yuji, Kinetic analysis of microwave-enhanced cellulose dissolution in ionic solvents, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c9cp06239d, 22, 3, 1003-1010, 2020.01. |
| 6. |
Shuntaro Tsubaki, Kiriyo Oono, Ayumu Onda, Takashi Kadono, Masao Adachi, Tomohiko Mitani, Microwave-assited solubilization of microalgae in high-temperature ethylene glycol, Biomass and Bioenergy, 10.1016/j.biombioe.2019.105360, 130, 105360, 2019.09. |
| 7. |
Tsubaki, Shuntaro; Oono, Kiriyo; Onda, Ayumu, Fractionation of plant-cuticle-based bio-oils by microwave-assisted methanolysis combined with hydrothermal pretreatment and enzymatic hydrolysis, HELIYON, 10.1016/j.heliyon.2019.e01887, 5, 6, 2019.06. |
| 8. |
Kishimoto, Fuminao; Matsuhisa, Masayuki; Imai, Takashi; Mochizuki, Dai; Tsubaki, Shuntaro; Maitani, Masato M.; Suzuki, Eiichi; Wada, Yuji, Remote Control of Electron Transfer Reaction by Microwave Irradiation: Kinetic Demonstration of Reduction of Bipyridine Derivatives on Surface of Nickel Particle, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 10.1021/acs.jpclett.9b00629, 10, 12, 3390-3394, 2019.06. |
| 9. |
S. Tsubaki, T. Matsuzawa, S. Fujii, Eiichi Suzuki, H. Kanamori, T. Hoshino, S. Hosoda, Y. Wada, In situ Raman monitoring of dielectric-heating-enhanced freeze-drying under different electromagnetic wave frequencies, RSC Advances, 2019, 9, 9001-9005, 2019.03. |
| 10. |
S. Tsubaki, S. Hayakawa, S. Ueda, S. Fujii, E. Suzuki, J. Zhang, A. Bond, Y. Wada, Radio frequency alternating electromagnetic field enhanced tetraruthenium polyoxometalate electrocatalytic water oxidation, Chemical Communications, 55, 8, 1032-1035, 2019.01. |
| 11. |
Shuntaro Tsubaki, Shogo Hayakawa, Tadaharu Ueda, Tomohiko Mitani, Ei-ichi Suzuki, Satoshi Fujii, Yuji Wada, Proton-Enhanced Dielectric Properties of Polyoxometalates in Water under Radio-Frequency Electromagnetic Waves, Materials, 10.3390/ma11071202, 11, 1202, 2018.07. |
| 12. |
Reversible Mechanochlomic Luminescence of a Heteroatom-Free Helically Chiral Hydrocarbon. |
| 13. |
Jun Fukushima, Shuntaro Tsubaki, Tomoki Matsuzawa, Keiichiro Kashimura, Tomohiko Mitani, Tomoaki Namioka, Satoshi Fujii, Naoki Shinohara, Hirotsugu Takizawa, Yuji Wada, Effect of Aspect Ratio on the Permittivity of GraphiteFiber in Microwave Heating, Materials, 11, 169, 2018.01. |
| 14. |
Fuminao Kishimoto, Kah Hon Leong, Shinichiro Kawamura, Naoto Haneishi, Shuntaro Tsubaki, Yuji Wada, Acceleration of Water Electrolysis by Accumulation of Microwave Energy at a Pt Disk Electrode, CHEMISTRY LETTERS, 10.1246/cl.170686, 46, 11, 1593-1596, 2017.11, The current density of water reduction using a commercial Pt disk electrode was enhanced under 2.45 GHz microwave irradiation. The transitional alternation of temperature distribution was explained with a heat-transfer simulation using COMSOL Multiphysics based on the finite element method. Results show that most of the microwave energy was converted into thermal energy at the vicinity of the Pt electrode. A local high-temperature region enhancing the water-reduction reaction was hence formed.. |
| 15. |
Satoshi Fujii, Shuntaro Tsubaki, Naomi Inazu, Eiichi Suzuki, Yuji Wada, Smelting of Scandium by Microwave Irradiation, Materials, 10, 1138, 2017.09. |
| 16. |
Satoshi Horikoshi, Takashi Minagawa, Shuntaro Tsubaki, Ayumu Onda, Nick Serpone, Is Selective Heating of the Sulfonic Acid Catalyst AC-SO3H by Microwave Radiation Crucial in the Acid Hydrolysis of Cellulose to Glucose in Aqueous Media?, CATALYSTS, 10.3390/catal7080231, 7, 8, 231, 2017.08, Selective heating of microwave-absorbing solid catalysts in a heterogeneous medium may affect a chemical reaction; such selectivity cannot be achieved by conventional oil-bath or steam heating methods. Moreover, microwave methods are often misunderstood with respect to equipment and temperature measurements, so that additional experimentation is necessary. In this regard, the present study intended to clarify the effect of microwave selective heating on acid hydrolytic processes using a sulfonated activated carbon catalyst (AC-SO3H). The model reaction chosen was the acid hydrolysis of cellulose carried out in a Pyrex glass microwave reactor, with the process being monitored by examining the quantity of total sugar, reducing sugar, and glucose produced. Heat transfer from the catalyst to the aqueous solution through absorption of microwaves by the catalyst occurred as predicted from a simulation of heat transfer processes. The resulting experimental consequences are compared with those from the more uniform microwave conduction heating method by also performing the reaction in a SiC microwave reactor wherein microwaves are absorbed by SiC. Some inferences of the influence of microwave selective heating of carbon-based catalyst particles are reported. Under selective heating conditions (Pyrex glass reactor), the yield of glucose from the acid hydrolysis of cellulose was 56% upon microwave heating at 200 degrees C, nearly identical with the yield (55%) when the hydrolytic process was performed under mainly conventional heating conditions in the SiC reactor. Although the beneficial effect of catalyst selective heating was not reflected in the reaction efficiency, there were substantial changes in the state of adsorption of cellulose on the catalyst surface.. |
| 17. |
Ayumu Onda, Sayuri Onda, Miyuki Koike, Kazumichi Yanagisawa, Shuntaro Tsubaki, Masanori Hiraoka, Catalytic Hydrolysis of Polysaccharides Derived from Fast-Growing Green Macroalgae, CHEMCATCHEM, 10.1002/cctc.201700100, 9, 14, 2638-2641, 2017.07, Green macroalgae, such as Ulva spp., has a higher growth rate than terrestrial lingocellulosic biomass, which often leads to serious environmental issues such as green tide. So, it is a promising feedstock for biorefineries. Hiraoka produced Ulva with reproducible compositions and sizes by our original cultivation method. The macroalgae contained approximately 35 wt% of a soluble polysaccharide called ulvan, which is a sulfated glucuronorhamnan polysaccharide. The catalytic conversion of extracted ulvan was performed under hydrothermal conditions at 130 degrees C by using solid acid catalysts. The Amberlyst 70 catalyst has a stable structure and gave monosaccharides in quantitative yield, predominantly in the form of rhamnose. The Amberlyst 70 catalyst showed higher activity than sulfonated activated- carbon (AC-SO3H) in the hydrothermal conversion of ulvan, although Amberlyst 70 showed lower catalytic activity than AC-SO3H in the hydrolysis of starch.. |
| 18. |
Masato M. Maitani, Hirokazu Satou, Aoi Ohmura, Shuntaro Tsubaki, Yuji Wada, Crystalline orientation control using self-assembled TiO2 nanosheet scaffold to improve CH3NH3PbI3 perovskite solar cells, Japanese Journal of Applied Physics, 56, 8S2, 08MC17, 2017.07. |
| 19. |
Naoto Haneishi, Shuntaro Tsubaki, Masato M. Maitani, Eiichi Suzuki, Satoshi Fujii, Yuji Wada, Electromagnetic and Heat-Transfer Simulation of the Catalytic Dehydrogenation of Ethylbenzene under Microwave Irradiation, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 10.1021/acs.iecr.7601413, 56, 27, 7685-7692, 2017.07, Electromagnetic and heat-transfer simulations were used to study the effects of microwave-generated nonuniform temperature distributions in a catalyst bed on the rate enhancement of a fixed-bed flow reaction. We used the dehydrogenation of ethylbenzene over a magnetite catalyst as a model reaction. During the microwave reaction, a temperature gradient was generated in the catalyst bed; the highest temperature occurred at the core of the catalyst bed, and it parabolically decreased toward the surface. Using these simulation results and Arrhenius parameters, the reaction rates were estimated by considering the nonuniform temperature distribution. The measured reaction rate was 36% larger than the simulated value, indicating that the rate enhancement under microwaves can, not only be attributed to the nonuniform temperature distribution in the catalyst bed. This could be due to nonequilibrium local heating (the so-called hot spot) in the very small region around the catalyst particle.. |
| 20. |
Hiroshi Yokawa, Hirokazu Mutou, Shuntaro Tsubaki, Naoto Haneishi, Takashi Fuji, Norio Asano, Keiichiro Kashimura, Tomohiko Mitani, Satoshi Fujii, Naoki Shinohara, Yuji Wada, Water vaporization from deposited sand by microwave cavity resonator, Journal of Civil & Environmental Engineering, 10.4172/2165-784X.1000279, 7, 4, 1000279-1000279, 2017.07. |
| 21. |
Masato M. Maitani, Daikichi Iso, Junbeom Kim, Shuntaro Tsubaki, Yuji Wada, Microwave Application to Efficient Annealing Process of CH3NH3PbI3 Perovskite Crystalline Films, ELECTROCHEMISTRY, 10.5796/electrochemistry.85.236, 85, 5, 236-240, 2017.05, As next-generation printable solar cells, perovskite solar cell utilizing organometal halide perovskite crystalline semiconductor as the active layer has been considered as one of the most promising systems for its high efficiency (> similar to 22%) and construction with low-cost materials. Annealing process of organometal halide perovskite crystalline films are, however, relatively time-consuming process for the perovskite solar cells. We propose the microwave heating applied to the annealing process of the CH3NH3PbI3 perovskite crystalline films for converting the intermediate state of as-coated precursor films into perovskite poly-crystalline films. Observed rapid conversion process into perovskite crystals with higher crystallinity and even the degradation of perovskite to be PbI2 by evaporation of methylammonium iodide at relatively lower temperature to the conventional hotplate heating imply a promising potential to achieve novel high throughput annealing process with high-quality crystallinity of perovskite films at low-temperature due to direct and effective heating of CH3NH3PbI3 films by the microwave irradiation. (C) The Electrochemical Society of Japan, All rights reserved.. |
| 22. |
Yuji Wada, Satoshi Fujii, Eiichi Suzuki, Masato M. Maitani, Shuntaro Tsubaki, Satoshi Chonan, Miho Fukui, Naomi Inazu, Smelting Magnesium Metal using a Microwave Pidgeon Method, SCIENTIFIC REPORTS, 10.1038/srep46512, 7, 46512, 2017.04, Magnesium (Mg) is a lightweight metal with applications in transportation and sustainable battery technologies, but its current production through ore reduction using the conventional Pidgeon process emits large amounts of CO2 and particulate matter (PM2.5). In this work, a novel Pidgeon process driven by microwaves has been developed to produce Mg metal with less energy consumption and no direct CO2 emission. An antenna structure consisting of dolomite as the Mg source and a ferrosilicon antenna as the reducing material was used to confine microwave energy emitted from a magnetron installed in a microwave oven to produce a practical amount of pure Mg metal. This microwave Pidgeon process with an antenna configuration made it possible to produce Mg with an energy consumption of 58.6 GJ/t, corresponding to a 68.6% reduction when compared to the conventional method.. |
| 23. |
Shuntaro Tsubaki, Kiriyo Oono, Masanori Hiraoka, Ayumu Onda, Tomohiko Mitani, Microwave-assisted hydrothermal extraction of sulfated polysaccharides from Ulva spp. and Monostroma latissimum, FOOD CHEMISTRY, 10.1016/j.foodchem.2016.04.121, 210, 311-316, 2016.11, Microwave-assisted hydrothermal extraction was applied for production of sulfated polysaccharides from Ulva spp. and Monostroma latissimum. The maximum ulvan yields attained 40.4 +/- 3.2% (Ulva meridionalis) and 36.5 +/- 3.1% (Ulva ohnoi) within 4 min of come-up time and 10 min of extraction time at 160 degrees C, respectively. The rhamnan sulfate yield from M. latissimum further attained 53.1 +/- 7.2% at 140 degrees C. The sulfated polysaccharides were easily recovered from the extract by simple ethanol precipitation. In addition, molecular weights and viscosity of the extracted polysaccharides could be controlled by varying the extraction temperature. Dielectric measurement revealed that ionic conduction was the important parameter that affect the microwave susceptibility of algae-water mixture. The sulfated polysaccharides extracts are expected as potential feedstock for medical and food applications. (C) 2016 Elsevier Ltd. All rights reserved.. |
| 24. |
Fuminao Kishimoto, Masayuki Matsuhisa, Shinichiro Kawamura, Satoshi Fujii, Shuntaro Tsubaki, Masato M. Maitani, Eiichi Suzuki, Yuji Wada, Enhancement of anodic current attributed to oxygen evolution on α-Fe2O3 electrode by microwave oscillating electric field, Scientific Reports, 10.1038/srep35554, 6, 35554, 2016.10. |
| 25. |
Taishi Ano, Fuminao Kishimoto, Dai Mochizuki, Shuntaro Tsubaki, Masato M. Maitani, Eiichi Suzuki, Yuji Wada, Distance-depending Photoinduced Electron Transfer at Two-dimensional Interface in Alternate Stacked Structures of Tantalate Nanosheets and Tungstate Nanosheets, CHEMISTRY LETTERS, 10.1246/cl.160526, 45, 9, 1111-1113, 2016.09, We demonstrate the electron transfer from the conduction band of tantalate nanosheets to that of tungstate nanosheets depending on the interlayer distance in the alternate-stacked structure prepared by the thiol-ene click reaction of thiol-grafted tantalate nanosheets and alkene-grafted tungstate nanosheets. The interlayer distance is precisely controlled from 0.93 to 1.64 nm by changing the methylene chain number of the organic bridges. The logarithm of the rate constant of the electron transfer decreases linearly with the distance.. |
| 26. |
Taishi Ano, Fuminao Kishimoto, Ryo Sasaki, Shuntaro Tsubaki, Masato M. Maitani, Eiichi Suzuki, Yuji Wada, In situ temperature measurements of reaction spaces under microwave irradiation using photoluminescent probes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c6cp02034h, 18, 19, 13173-13179, 2016.05, We demonstrate two novel methods for the measurement of the temperatures of reaction spaces locally heated by microwaves, which have been applied here to two example systems, i.e., BaTiO3 particles covered with a SiO2 shell (BaTiO3-SiO2) and layered tungstate particles. Photoluminescent (PL) probes showing the temperature-sensitivity in their PL lifetimes are located in the nanospaces of the above systems. In the case of BaTiO3-SiO2 core-shell particles, rhodamine B is loaded into the mesopores of the SiO2 shell covering the BaTiO3 core, which generates the heat through the dielectric loss of microwaves. The inner nanospace temperature of the SiO2 shell is determined to be 28 degrees C higher than the bulk temperature under microwave irradiation at 24 W. On the other hand, Eu3+ is immobilized in the interlayer space of layered tungstate as the PL probe, showing that the nanospace temperature of the interlayer is only 4 degrees C higher than the bulk temperature. This method for temperature-measurement is powerful for controlling microwave heating and elucidates the ambiguous mechanisms of microwave special effects often observed in chemical reactions, contributing greatly to the practical application of microwaves in chemistry and materials sciences.. |
| 27. |
Shuntaro Tsubaki, Kiriyo Oono, Ayumu Onda, Kazumichi Yanagisawa, Tomohiko Mitani, Jun-ichi Azuma, Effects of ionic conduction on hydrothermal hydrolysis of corn starch and crystalline cellulose induced by microwave irradiation, CARBOHYDRATE POLYMERS, 10.1016/j.carbpol.2015.11.022, 137, 10, 594-599, 2016.02, This study investigated the effects of ionic conduction of electrolytes under microwave field to facilitate hydrothermal hydrolysis of corn starch and crystalline cellulose (Avicel), typical model biomass substrates. Addition of 0.1 M NaCl was effective to improve reducing sugar yield by 1.61-fold at unit energy (kJ) level. Although Avicel cellulose was highly recalcitrant to hydrothermal hydrolysis, addition of 0.1 M MgCl2 improved reducing sugar yield by 6.94-fold at unit energy (kJ). Dielectric measurement of the mixture of corn starch/water/electrolyte revealed that ionic conduction of electrolytes were strongly involved in facilitating hydrothermal hydrolysis of polysaccharides. (C) 2015 Elsevier Ltd. All rights reserved.. |
| 28. |
Euis Hermiati, Shuntaro Tsubaki, Jun-ichi Azuma, Cassava pulp hydrolysis under microwave irradiation with oxalic acid catalyst for ethanol production, Journal of Mathematical and Fundamental Sciences, 10.5614/j.math.fund.sci.2014.46.2.2, 46, 2, 125-139, 2014.05. |
| 29. |
Shuntaro Tsubaki, Kiriyo Oono, Masanori Hiraoka, Tadaharu Ueda, Ayumu Onda, Kazumichi Yanagisawa, Jun-ichi Azuma, Hydrolysis of green-tide forming Ulva spp. by microwave irradiation with polyoxometalate cluster, Green Chemistry, 10.1039/C3GC42027B, 16, 2277-2233, 2013.12. |
| 30. |
Shuntaro Tsubaki, Kazuki Sugimura, Yoshikuni Teramoto, Keizo Yonemori, Jun-ichi Azuma, Cuticular Membrane of Fuyu Persimmon Fruit Is Strengthened by Triterpenoid Nano-Fillers, PLOS ONE, 10.1371/journal.pone.0075275, 8, 9, e75275, 2013.09, The mechanical defensive performance of fruit cuticular membranes (CMs) is largely dependent on the molecular arrangement of their constituents. Here, we elucidated nano-sized interactions between cutin and triterpenoids in the cuticular matrix of Fuyu persimmon fruits (Diospyros kaki Thunb. cv. Fuyu), focusing on the mechanical properties using a combination of polymer analyses. The fruit CMs of Fuyu were primarily composed of wax (34.7%), which was predominantly triterpenoids followed by higher aliphatic compounds, and cutin (48.4%), primarily consisting of 9,10-epoxy-18-hydroxyoctadecanoic acid and 9,10,18-trihydroxyoctadecanoic acid. Based on the tensile tests of the CM, the removal of wax lead to a considerable decrease in the maximum stress and elastic modulus accompanied by an increase in the maximum strain, indicating that wax is of significant importance for maintaining the mechanical strength of the CM. Wide-angle X-ray diffraction and relaxation time measurements using solid-state C-13 nuclear magnetic resonance indicated that the triterpenoids in the cuticular matrix construct a nanocomposite at a mixing scale below 20-24 nm; however, the higher aliphatic compounds did not exhibit clear interactions with cutin. The results indicated that the triterpenoids in the cuticular matrix endow toughness to the CM by functioning as a nanofiller.. |
| 31. |
Shuntaro Tsubaki, Kiriyo Oono, Tadaharu Ueda, Ayumu Onda, Kazumichi Yanagisawa, Tomohiko Mitani, Jun-ichi Azuma, Microwave-assisted hydrolysis of polysaccharides over polyoxometalate clusters, BIORESOURCE TECHNOLOGY, 10.1016/j.biortech.2013.06.092, 144, 67-73, 2013.09, Polyoxometalate (POM) clusters were utilized as recyclable acid catalysts and microwave-absorbing agents for the microwave-assisted hydrolysis of corn starch and crystalline cellulose. Phosphotungstic (PW) and silicotungstic (SiW) acids showed high hydrolyzing activity, while phosphomolybdic acid (PMo) showed lower glucose stability. The PW catalyst could be recycled by ether extraction at least 4 times without changing its catalytic activity. The addition of PW could reduce the energy demand required for running the hydrolysis by 17-23%. The dielectric property of the aqueous PW solution was important for increasing the microwave-absorption capability of the reaction system and reducing the energy consumption. (C) 2013 Elsevier Ltd. All rights reserved.. |
| 32. |
Shuntaro Tsubaki, Kiriyo Oono, Ayumu Onda, Kazumichi Yanagisawa, Jun-ichi Azuma, Comparative decomposition kinetics of neutral monosaccharides by microwave and induction heating treatments, CARBOHYDRATE RESEARCH, 10.1016/j.carres.2013.04.013, 375, 1-4, 2013.06, The stabilities of five neutral monosaccharides (glucose, galactose, mannose, arabinose, and xylose) were kinetically compared after the molecules were submitted to microwave heating (internal heating) and induction heating (external heating) under completely identical thermal histories by employing PID (proportional, integral, and derivative) temperature controlled ovens and homogeneous mixing. By heating in water at 200 degrees C, the rate constants for the decomposition reactions varied from 2.13 x 10 (4) to 3.87 x 10 (4) s (1) for microwave heating; however, the values increased by 1.1-to 1.5-fold for induction heating. Similarly, in a dilute (0.8%) sulfuric acid solution, the decomposition rate constants varied from 0.61 x 10 (3) to 2.00 x 10 (3) s (1) for microwave heating; however, the values increased by 1.5-to 2.2-fold for induction heating. The results show that microwave heating imparts greater stability to neutral monosaccharides than does induction heating. The undesirable decomposition of monosaccharides at the surface boundary of reactor walls may have increased the probability of monosaccharide decomposition during induction heating. (C) 2013 Elsevier Ltd. All rights reserved.. |
| 33. |
Shuntaro Tsubaki, Shunichi Sakumoto, Norihiro Uemura, Jun-ichi Azuma, Compositional analysis of leaf cuticular membranes isolated from tea plants (Camellia sinensis L.), FOOD CHEMISTRY, 10.1016/j.foodchem.2012.10.116, 138, 1, 286-290, 2013.05, Chemical constituents of cuticular membranes (CMs) isolated from three tea cultivars (Camellia sinensis (L) O. Kuntze cvs. Yabukita, Samidori and Gokou) were compared. All CMs from the adaxial side of the leaves showed higher accumulation of wax, cutin and polysaccharide, while those from the abaxial side were abundant in cutan, showing the adaptation of the adaxial side to abiotic stresses, such as wind and rain, in contrast to the abaxial side, which provides defence against pathogens. Yabukita, a major tea cultivar in Japan, developed thick CMs while Samidori and Gokou, shade-cultivated tea cultivars, had lighter CMs, reflecting their thin and soft leaves. CMs rapidly accumulated 9,10-epoxy-18-hydroxyoctadecanoic acid at a very early stage of leaf development. Additionally, shade treatment did not influence cutin biosynthesis in CMs, reflecting high adaptation of tea leaves under low light levels. (C) 2012 Elsevier Ltd. All rights reserved.. |
| 34. |
Shuntaro Tsubaki, Jun-ichi Azuma, Total fractionation of green tea residue by microwave-assisted alkaline pretreatment and enzymatic hydrolysis, BIORESOURCE TECHNOLOGY, 10.1016/j.biortech.2013.01.001, 131, 485-491, 2013.03, Total refinery of constituents of green tea residue was achieved by combination of microwave-assisted alkaline pretreatment and enzymatic hydrolysis. Alkaline pretreatment was effective at separating pectic polysaccharides, protein, phenolic compounds and aliphatic compounds (probably originating from cuticular components), and the solubilization rate was attained 64-74% by heating at 120-200 degrees C. The higher heating value (HHV) of alkali-soluble fraction attained 20.1 MJ/kg, indicating its usability as black-liquor-like biofuel. Successive cellulolytic enzymatic hydrolysis mainly converted cellulose into glucose and attained the maximum solubilization rate of 89%. Final residue was predominantly composed of aliphatic cuticular components with high proportion in 9,10,18-trihydroxyoctadecanoic acid (30.1-48.6%). These cuticular components are potential alternative feedstock for aliphatic compounds commonly found in oil plants. (C) 2013 Elsevier Ltd. All rights reserved.. |
| 35. |
Shuntaro Tsubaki, Kiriyo Oono, Ayumu Onda, Kazumichi Yanagisawa, Jun-ichi Azuma, Microwave-assisted hydrothermal hydrolysis of cellobiose and effects of additions of halide salts, BIORESOURCE TECHNOLOGY, 10.1016/j.biortech.2012.07.086, 123, 703-706, 2012.11, Microwave irradiation was compared with induction heating for hydrothermal hydrolysis of cellobiose. Microwave heating improved glucose selectivity and resulted in a pH of the hydrolyzates that was = 10 mM reduced the required microwave output to 58.6-66.2% as compared to conventional microwave-hydro-thermal hydrolysis without halide salts. Kinetic analyses revealed that the addition of salt increased the hydrolysis rate by increasing the frequency factor of the reaction. The results showed that microwave irradiation in the presence of microwave-absorbing salts is effective for hydrothermal hydrolysis of carbohydrates. (C) 2012 Elsevier Ltd. All rights reserved.. |
| 36. |
Jun-ichi Azuma, Shuntaro Tsubaki, Masahiro Sakamoto, Rike Yudianti, Euis Hermiati, Refinery of biomass by utilization of specific effects of microwave irradiation, Procedia Chemistry, 10.1016/j.proche.2012.06.003, 4, 17-25, 2012.08. |
| 37. |
Yuki Takahashi, Shuntaro Tsubaki, Masahiro Sakamoto, Shin Watanabe, Jun-Ichi Azuma, Growth-dependent chemical and mechanical properties of cuticular membranes from leaves of Sonneratia alba, PLANT CELL AND ENVIRONMENT, 10.1111/j.1365-3040.2012.02482.x, 35, 7, 1201-1210, 2012.07, Chemical and mechanical properties of the leaf cuticular membranes (CMs) of a mangrove, Sonneratia alba J. Smith, were analysed at various leaf development stages to evaluate their tolerance to environmental stress. Our analyses demonstrate that the CMs from leaves of S. alba at different growth stages are generally rich in wax (21.525.7%) and cutin (52.463.4%) which rapidly accumulate at the early stages of leaf growth, while cutan (4.310.3%) and polysaccharide (2.37.7%) continuously accumulate throughout growth. Immature CMs are physically weak and highly viscoelastic. However, CMs become strengthened and stiffened during leaf expansion and maturation (by factors of about 1.5 and 2.4, respectively) while their flexibility decreases (6883% decrease). Finally, the CMs lose their strength at the senescent stage (3043% decreasement). Correlation analysis between chemical composition and mechanical properties revealed that the cutin matrix is mainly responsible for the high viscoelastic properties of CMs, while wax, cutan and polysaccharide contributed to their elasticity. Wax also affected the strength of the CMs, whereas cutan and polysaccharide showed rigidizing effect. Rapid accumulation of wax and cutin in the CMs after bud burst followed by the mechanical supports of cutan and polysaccharide in an isolateral manner contributed to the remarkable environmental tolerance of S. alba.. |
| 38. |
Shuntaro Tsubaki, Yoshihiko Ozaki, Keizo Yonemori, Jun-ichi Azuma, Mechanical properties of fruit-cuticular membranes isolated from 27 cultivars of Diospyros kaki Thunb., FOOD CHEMISTRY, 10.1016/j.foodchem.2011.12.039, 132, 4, 2135-2139, 2012.06, Fruit cuticular membranes (CMs) were isolated from 27 cultivars of Diospyros kaki Thunb., and relationships among their chemical compositions, densities and mechanical properties were analysed. Wide cultivar dependency was observed in both chemical compositions and mechanical properties, however, astringency did not show clear correlation with them. Densities of the CMs showed significant positive correlation with maximum stress and elastic modulus, but negative correlation with maximum strain. Positive correlations were also observed in elastic modulus-polysaccharide content and maximum strain-polysaccharide content, and negative correlation in elastic modulus-cutin content on a weight over unit area (mu g/cm(2)) basis. The integration of densities of fruit CMs and their chemical constituents may explain the mechanical properties which are specific to each cultivar of D. kaki fruit. (C) 2011 Elsevier Ltd. All rights reserved.. |
| 39. |
Euis Hermiati, Jun-ichi Azuma, Shuntaro Tsubaki, Djumali Mangunwidjaja, Titi C. Sunarti, Ono Suparno, Bambang Prasetya, Improvement of microwave-assisted hydrolysis of cassava pulp and tapioca flour by addition of activated carbon, CARBOHYDRATE POLYMERS, 10.1016/j.carbpol.2011.08.033, 87, 1, 939-942, 2012.01, The superior effects of addition of activated carbon were evidenced for microwave assisted hydrolysis of starches in cassava pulp and tapioca flour under hydrothermal conditions varying irradiation temperature (160-230 degrees C at 5 min), duration of heating time (5-18 min at 210 degrees C) and amount of activated carbon at 0.5-2.0:1:20 of activated carbon:solid:liquid ratio. The presence of 1.0 g/g in microwave-assisted hydrolysis gave much improved glucose yields (44.49% for cassava pulp and 71.93% for tapioca flour) at lower heating temperature (220 degrees C and 200 degrees C, each for 5 min) with suppressed formation of secondary decomposed compounds than those without addition of activated carbon (32.41% in cassava pulp at 230 degrees C and 55.11% in tapioca flour at 240 degrees C, each for 5 min). The highest glucose yield from cassava pulp (52.27%) was obtained after heating at 210 degrees C for 15 min. (C) 2011 Elsevier Ltd. All rights reserved.. |
| 40. |
Yuki Takahashi, Shuntaro Tsubaki, Masahiro Sakamoto, Shin Watanabe, Wahyu Dwianto, Jun-ichi Azuma, Chemical and mechanical properties of cuticular membranes isolated from leaves of Sonneratia alba, Wood Research Journal, 10.51850/wrj.2011.2.1.69-72, 2, 1, 69-72, 2011.06. |
| 41. |
Akikazu Matsumoto, Shuntaro Tsubaki, Masahiro Sakamoto, Jun-ichi Azuma, A novel saccharification method of starch using microwave irradiation with addition of activated carbon, BIORESOURCE TECHNOLOGY, 10.1016/j.biortech.2010.12.013, 102, 4, 3985-3988, 2011.02, Activated carbons were investigated for their heat catalytic effects to improve saccharification of starch by autohydrolysis in water under microwave electromagnetic field, and the results were compared with graphite and carbon nanotubes. The activated carbons with low adsorptive capacity of maltose showed high saccharification rate, while those with high adsorptive capacity exhibited low saccharification. In addition, the former activated carbons decreased the saccharification temperature by 10-30 degrees C. Maltooligosaccharides produced in the presence of the latter activated carbons were recovered by desorption with 50% aqueous ethanol. The results indicated that both adsorptive capacities of maltooligosaccharides and catalytic effects of hot spots arisen from the uneven surface structure of activated carbons might contribute to the improvement in starch saccharification. (C) 2010 Elsevier Ltd. All rights reserved.. |
| 42. |
Shuntaro Tsubaki, Masahiro Sakamoto, Jun-ichi Azuma, Microwave-assisted extraction of phenolic compounds from tea residues under autohydrolytic conditions, FOOD CHEMISTRY, 10.1016/j.foodchem.2010.05.088, 123, 4, 1255-1258, 2010.12, Phenolic compounds were extracted from three kinds of tea residues (green, oolong and black tea residues) by microwave-assisted extraction in water under autohydrolytic conditions without using any catalyst or organic solvent. Productions of phenolic compounds were enhanced by microwave heating at 230 C. The main phenolic constituent in the extract from green tea residue was pyrogallol (24.6%) which was estimated to be originated from degradations of catechins. Derivatives of guaiacyl units of lignin such as dihydroconiferyl alcohol (10.3%) and vanillin (8.1%) were, however, the main constituents in oolong tea residue. In the case of black tea residue, derivatives of both catechins and lignin were comparably extracted. These phenolic compounds are interesting as a bio-based chemical feedstock such as phenolic precursors and antioxidants. (C) 2010 Elsevier Ltd. All rights reserved.. |
| 43. |
Tsuyoshi Inoue, Shuntaro Tsubaki, Kazunori Ogawa, Kiyotaka Onishi, Jun-ichi Azuma, Isolation of hesperidin from peels of thinned Citrus unshiu fruits by microwave-assisted extraction, FOOD CHEMISTRY, 10.1016/j.foodchem.2010.04.051, 123, 2, 542-547, 2010.11, Simultaneous extraction by microwave-irradiation and crystallisation were performed in the same pot of solvent of 70% (v/v) aqueous ethanol for isolation of hesperidin from thinned immature fruit peels of Citrus unshiu as refining of Citrus waste biomass. The hesperidin content in immature fruits peels was about 3.2-fold higher than that of mature fruit. After microwave-assisted extraction (MAE), the yield of hesperidin reached 58.6 mg/g, which was comparable to the amount obtained after extraction using DMSO:methanol (1:1, v/v) as a solvent for 30 min at room temperature. Heating temperature and time for isolation of hesperidin crystallites were optimised as 140 degrees C and 8 min by using response surface methodology. Under this optimal condition, 86.8% (47.7 mg/g) of total hesperidin was isolable by MAE and low-temperature storage (5 degrees C, 24 h). (c) 2010 Elsevier Ltd. All rights reserved.. |
| 44. |
Tomoki Yoshida, Shuntaro Tsubaki, Yoshikuni Teramoto, Jun-ichi Azuma, Optimization of microwave-assisted extraction of carbohydrates from industrial waste of corn starch production using response surface methodology, BIORESOURCE TECHNOLOGY, 10.1016/j.biortech.2010.05.011, 101, 20, 7820-7826, 2010.10, Microwave-assisted extraction (MAE) was applied for production of carbohydrates mainly consisting of arabinoxylan from corn pericarp which is an industrial waste of corn starch production by using hot compressed water as a solvent. The solubilization rate increased with increase in heating temperature and reached 75.2% at 220 degrees C. The main extracted materials were carbohydrates consist of glucose, xylose and arabinose indicating solubilization of starch and hemicellulose, while residues were composed of cellulose. Four independent variables (heating temperature, come-up time, heating time and solid to liquid ratio) were optimized for maximizing the carbohydrates yield using the response surface methodology including fractional factorial design, the path of steepest ascent and central composite design. The optimized condition was as follows; heating temperature 176.5 degrees C, come-up time 2 min, heating time 16 min and solid to liquid ratio 1/20 (g/mL), respectively. The maximal yield attained 70.8% of carbohydrates with predominant production of xylo-oligosaccharides. (C) 2010 Elsevier Ltd. All rights reserved.. |
| 45. |
Jun-ichi Azuma, Shuntaro Tsubaki, Rike Yudianti and Myrtha Karina, Characterization of cuticle layer of Ilex latifolia, Wood Research Journal, 10.51850/wrj.2010.1.1.56-63, 1, 56-63, 2010.06. |
| 46. |
S. Tsubaki, Y. Ozaki, J. Azuma, Microwave-Assisted Autohydrolysis of Prunus mume Stone for Extraction of Polysaccharides and Phenolic Compounds, JOURNAL OF FOOD SCIENCE, 10.1111/j.1750-3841.2009.01466.x, 75, 2, C152-C159, 2010.03, Stone of Prunus mume (P. mume) is a by-product of pickled P. mume industry. Stones of native and pickled P. mume, mainly composed of holocellulose (83.8 +/- 1.8% and 65.1 +/- 0.3%, respectively) and acid-insoluble lignin (25.3 +/- 2.2% and 30.6 +/- 0.9%, respectively), were autohydrolyzed by microwave heating to extract polysaccharides and phenolic compounds. By heating at 200 to 230 degrees C, 48.0% to 60.8% of polysaccharide and 84.1% to 97.9% of phenolic compound were extracted in water along with partial degradation of hemicelluloses and lignin. The extracted liquors showed antioxidant activity against hydroxyl radical and DPPH radical originated from phenolic compounds. The pickled P. mume stone showed higher autohydrolyzability and microwave absorption capacity than the native stone due to absorbed salts and acids during pickling in fruit juice of P. mume with external addition of sodium chloride. Pickling process in salty and weak acidic juice seemed to be a kind of pretreatment for softening the stones prior to autohydrolysis induced by microwave heating.. |
| 47. |
Shuntaro Tsubaki, Michiyo Nakauchi, Yoshihiko Ozaki, Jun-ichi Azuma, Microwave Heating for Solubilization of Polysaccharide and Polyphenol from Soybean Residue (Okara), FOOD SCIENCE AND TECHNOLOGY RESEARCH, 10.3136/fstr.15.307, 15, 3, 307-314, 2009.05, Okara, a soybean by-product of tofu production, was treated with microwave irradiation in water for solubilization of its components. The solubilization rate increased with increasing temperature and reached higher than 70% around 200 degrees C with a heating time of 7 min. The main solubilized components were neutral carbohydrates consisting of arabinose and galactose, while the residues were mainly composed of cellulose. LV-SEM images confirmed solubilization of cell wall components. Production of new polyphenolic compounds that have antioxidant activity was observed above 180 degrees C. The heating temperature and heating time were optimized for neutral carbohydrate solubilization using the response surface methodology. The optimized condition was heating at 196 degrees C for 2 min, indicating that a short heating time is effective for solubilization of carbohydrates to prevent secondary decomposition.. |
| 48. |
Shuntaro Tsubaki, Hiroyuki IIda, Masahiro Sakamoto, Jun-Ichi Azuma, Microwave Heating of Tea Residue Yields Polysaccharides, Polyphenols, and Plant Biopolyester, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, 10.1021/jf802253s, 56, 23, 11293-11299, 2008.12, Microwave heating was used to produce aqueous-soluble components from green, oolong, and black tea residues. Heating at 200-230 degrees C for 2 min extracted 40-50% of polysaccharides and 60-70% of the polyphenols. Solubilization of arabinose and galactose by autohydrolysis occurred with heating above 170 degrees C, whereas heating above 200 degrees C was necessary to solubilize xylose. Catechins were soluble in water by heating at low temperature (110 degrees C); however, new polyphenols having strong antioxidant activity were produced above 200 degrees C. The amount of solubilized materials and antioxidant activity increased with increased fermentation of harvested tea leaves (green tea |
| 49. |
Tsubaki, S.; Oono, K.; Onda, A.; Ueda, T.; Mitani, T.; Hiraoka, M., Microwave-assisted hydrolysis of biomass over activated carbon supported polyoxometalates, RSC ADVANCES, 10.1039/c6ra28778f, 7, 20, 12346-12350. |
| 50. |
Hiraoka, Masanori; Ichihara, Kensuke; Zhu, Wenrong; Shimada, Satoshi; Oka, Naohiro; Cui, Jianjun; Tsubaki, Shuntaro; He, Peimin
, Examination of species delimitation of ambiguous DNA-based Ulva (Ulvophyceae, Chlorophyta) clades by culturing and hybridisation, PHYCOLOGIA, 10.2216/16-109.1, 56, 5, 517-532. |
