Elsevier BV Acta Medica Okayama 0921-8831 36 10 2025 Evaluating the effects of electrolytes on the interaction forces between alumina surfaces in polyacrylic acid solutions using atomic force microscopy 105028 EN Naoto Kishimoto Graduate School of Natural Science and Technology, Okayama University Ryota Kaji Faculty of Science and Engineering, Doshisha University Katsumi Tsuchiya Faculty of Science and Engineering, Doshisha University Koreyoshi Imamura Graduate School of Natural Science and Technology, Okayama University Naoyuki Ishida Faculty of Science and Engineering, Doshisha University Evaluation and control of ceramic slurry at the microscopic level are critical to ensure consistent quality in manufactured ceramics. Notably, metal ions such as Mg2+ and Al3+ are common in ceramic slurries and significantly influence the stability of particle. This study applied atomic force microscopy to investigate the interaction forces between alumina particle surfaces in the presence of different concentrations of three metal ions and polyacrylic acid (PAA), a widely used dispersant.<br> The attractive forces observed at low PAA concentrations were attributed to polymer bridging between alumina surfaces, whereas the repulsive forces observed at high PAA concentrations were attributed to the domination of steric repulsion between adsorbed PAA molecules. The presence of multivalent metal ions, such as Mg2+ and Al3+, modulated these interactions; an increasing ion valence induced a transition from repulsive to attractive force, primarily owing to electrostatic screening, which caused conformational collapse of the PAA chains and diminished the range of steric repulsion. Similarly, increasing the concentration of these metal ions decreased the range of repulsive forces, eventually resulting in a net attraction driven by the same electrostatic and polymer conformation mechanisms. Notably, the addition of 0.1 M AlCl3 produced an anomalous long-range attraction between surfaces that could not be explained by conventional mechanisms, such as polymer bridging or electrostatic interactions between charge domains. No potential conflict of interest relevant to this article was reported.

Informa UK Limited Acta Medica Okayama 0737-3937 43 6 2025 Spray-drying of polymer solutions across a broad concentration range and the subsequent formation of a few micro- ∼nano-meter sized fibers 1108 1116 EN Chika Araga Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Kaito Fukushima Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Haruna Sato Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Nao Honda Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Takato Hasegawa Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Koichi Nakaso Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Naoyuki Ishida Department of Chemical Engineering and Material Sciences, Faculty of Science and Engineering, Doshisha University Koreyoshi Imamura Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Spray drying is a widely utilized technique for the concentration and fine particulation of dried products. This study demonstrated that a versatile spray dryer, equipped with a two-fluid nozzle atomizer, can convert polymer solutions into nanoscale fibers by manipulating the conditions of the polymer solutions. The polymers employed in this research included polyvinylpyrrolidones (Mw 24.5 k to 60 kDa), dextrans (70 k to 450–650 kDa), pullulan, gum Arabic, Eudragit and agar, with methanol and water serving as solvents. Various combinations of polymers and solvents were subjected to spray drying at polymer concentrations ranging from 5 to 1000 g/L. Scanning electron microscopy analyses of the spray-dried samples indicated that the products transitioned from micrometer-sized particles to sub-micrometer fibers in several instances when the polymer concentrations exceeded specific threshold levels. The investigation also explored the relationship between these threshold concentrations and the surface tension and viscosity of the polymer solutions. No potential conflict of interest relevant to this article was reported.

Informa UK Limited Acta Medica Okayama 0737-3937 42 2 2023 Flavor retention characteristics of amorphous solid dispersion of flavors, prepared by vacuum-foam- and spray-drying under different conditions 227 237 EN Yuna Nitta Department of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Haruna Sato Department of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Rina Yamamoto Department of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Hiroyuki Imanaka Department of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Naoyuki Ishida Department of Chemical Engineering and Material Sciences, Faculty of Science and Engineering, Doshisha University Koreyoshi Imamura Department of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University We investigated the powderization of flavoring substances, using an amorphous solid dispersion (ASD) technique, in which hydrophobic molecules are separately embedded in a water-soluble carrier matrix. Six flavors, five carrier forming materials (polyvinylpyrrolidone/disaccharides), two solvents (methanol/ethanol) and two drying methods (vacuum-foam-/spray-drying) were employed. The drying conditions for the two drying processes were first examined, and under the optimal drying conditions, various flavor-carrier combinations and compositions of ASD samples were prepared and their flavor retention after drying and during storage under a vacuum were compared. Results demonstrated that flavor loss during drying and storage was minimized when the material was vacuum-foam-dried with polyvinylpyrrolidone. Vacuum-foam-drying in the presence of α-maltose or palatinose also resulted in a greater retention of flavor during drying and storage than a typical O/W emulsification-based powderization. These findings suggest that the ASD-based powderization of flavoring materials is a feasible alternative to the currently used produces. No potential conflict of interest relevant to this article was reported.

Elsevier Acta Medica Okayama 0260-8774 292 2021 Crystallization characteristics of amorphous trehalose dried from alcohol 110325 EN Takanari Sekitoh Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Takashi Okamoto Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Akiho Fujioka Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Tomohiko Yoshioka Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Shinji Terui Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Hiroyuki Imanaka Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Naoyuki Ishida Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Koreyoshi Imamura Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Trehalose forms a glass that can be used to preserve labile substances under desiccation. The crystallization characteristics, namely crystallization temperature (Tcry) and isothermal crystallization behavior of amorphous trehalose, dried from alcohol (methanol, ethanol), was analyzed and the results were compared with those for the amorphous trehalose freeze-dried from water. The use of alcohol as a solvent lowered the Tcry from 184 ± 6 °C for the case of an aqueous solvent to 103 ± 5 °C/methanol and 120 ± 8 °C/ethanol. The formation of multiple forms of crystals and partial melting were suggested by the thermal analysis. Isothermal crystallization experiments showed that the alcohol-originated amorphous trehalose was eventually exclusively converted into β-form crystals. The induction period (tind) before the start of isothermal crystallization was markedly shortened when alcohol was used as the solvent compared to water. The tind values for various amorphous sugar samples including the alcohol-originated ones could be correlated with difference between Tcry and the sample temperature. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 1349-6115 44 2010 Effects of the Cultivation Method on the Characteristics or Gene Expression Profiles of Aspergillus oryzae Using mCD or DPY Media 73 83 EN Hiroyuki Imanaka Soukichi Tanaka Bin Feng Koreyoshi Imamura Kazuhiro Nakanishi 10.18926/19962 We used modified Czapek-Dox (mCD) or dextrin-peptone-yeast extract (DPY) media to cultivate a filamentous fungus, Aspergillus oryzae IAM 2706 by three different cultivation methods, i.e., shaking-flask culture (SFC), agar-plate culture (APC), and membrane-surface liquid culture (MSLC), to identify the differences in cultivation behaviors and gene transcriptional profiles. The fungi cultivated by APC or MSLC secreted a greater number of different proteins/enzymes in larger quantities compared with fungi cultivated by SFC, particularly when DPY medium was used. In particular, the amounts of protease secreted by fungi cultivated via MSLC or APC were much greater compared with SFC. When mCD medium was used, α-amylase activity was barely detectable in all cultures while the activity was detected in MSLC and APC in a quantity that was several times higher than that in SFC using DPY medium. SDS-PAGE analysis and N-terminal amino acid sequences confirmed 6 proteins in the culture supernatants when DPY medium was used. Among these proteins oryzin (an alkaline protease) and α-amylase were detected at much higher levels in APC and MSLC compared with SFC, which was consistent with the measured activity of the secreted enzymes. However, when mCD medium was used, only oryzin was detected in significant amounts in MSLC and APC. Microarray analyses of the fungi cultivated by SFC, APC or MSLC using either mCD or DPY media indicated that the gene transcriptional profile of the MSLC sample was similar to that of the APC sample but different from that of the SFC sample. When mCD medium was used, most of the genes that were up-regulated 10-folds or greater in the MSLC sample relative to the SFC sample were unknown or predicted proteins. Transcription of the oryzin gene was only slightly up-regulated in the MSLC sample while transcription of the α-amylase gene was slightly down-regulated. On the other hand, when DPY medium was used, many known genes including the oryzin gene were up-regulated in the MSLC sample versus the SFC sample. No potential conflict of interest relevant to this article was reported.