Mitsumasa Osada

Non-catalytic synthesis of Chromogen I and III from N-acetyl-D-glucosamine in high-temperature water

Non-catalytic synthesis of 2-acetamido-2,3-dideoxy-D-erythro-hex-2-enofuranose (Chromogen I) and 3-acetamido-5-(1′,2′-dihydroxyethyl)furan (Chromogen III) from N-acetyl-D-glucosamine (GlcNAc) was achieved, with the highest yields of 23.0% and 23.1%, respectively, in high-temperature water at 120–220 °C and 25 MPa with a reaction time of 7–39 s.

Effect of purification method of β-chitin from squid pen on the properties of β-chitin nanofibers.

The relationship between purification methods of β-chitin from squid pen and the physicochemical properties of β-chitin nanofibers (NFs) were investigated. Two types of β-chitin were prepared, with β-chitin (a→b) subjected to acid treatment for decalcification and then base treatment for deproteinization, while β-chitin (b→a) was treated in the opposite order. These β-chitins were disintegrated into NFs using wet pulverization. The β-chitin (b→a) NF dispersion has higher transmittance and viscosity than the β-chitin (a→b) NF dispersion. For the first time, we succeeded in obtaining 3D images of the β-chitin NF dispersion in water by using quick-freeze deep-etch replication with high-angle annular dark field scanning transmission electron microscopy. The β-chitin (b→a) NF dispersion has a denser and more uniform 3D network structure than the β-chitin (a→b) NF dispersion. Widths of the β-chitin (a→b) and (b→a) NFs were approximately 8-25 and 3-10nm, respectively.

Non-catalytic dehydration of N,N′-diacetylchitobiose in high-temperature water

Non-catalytic synthesis of 4-O-β-2-acetamido-2-deoxy-D-glucopyranosyl 2-acetamido-2,3-dideoxydidehydro-glucopyranose (GND) from chitin disaccharide, N,N′-diacetylchitobiose (GlcNAc)2, was achieved, with a maximum yield of 24.7% in high-temperature water at 120–220 °C and 25 MPa with a reaction time of 8–39 s.

Effect of acidity on the physicochemical properties of α- and β-chitin nanofibers

We have investigated whether acidity can be used to control the physicochemical properties of chitin nanofibers (ChNFs). In this study, we define acidity as the molar ratio of dissociated protons from the acid to the amino groups in the raw chitin powder. The effect of acidity on the physicochemical properties of α- and β-ChNFs was compared. The transmittance and viscosity of the β-ChNFs drastically and continuously increased with increasing acidity, while those of the α-ChNFs were not affected by acidity. These differences are because of the higher ability for cationization based on the more flexible crystal structure of β-chitin than α-chitin. In addition, the effect of the acid species on the transmittance of β-ChNFs was investigated. The transmittance of β-ChNFs can be expressed by the acidity regardless of the acid species, such as hydrochloric acid, phosphoric acid, and acetic acid. These results indicate that the acidity defined in this work is an effective parameter to define and control the physicochemical properties of ChNFs.

NMR spectroscopic structural characterization of a water-soluble β-(1 → 3, 1 → 6)-glucan from Aureobasidium pullulans

An unambiguous structural characterization of the water-soluble Aureobasidium pullulans β-(1→3, 1→6)-glucan is yet to be achieved, although this β-(1→3, 1→6)-glucan is expected to exhibit excellent biofunctional properties. Thus, we herein report the elucidation of the primary structure of the A. pullulans β-(1→3, 1→6)-glucan using nuclear magnetic resonance spectroscopy, followed by comparison of the obtained structure with that of schizophyllan (SPG). Structural characterization of the A. pullulans β-(1→3, 1→6)-glucan revealed that the structural units are a β-(1→3)-d-glucan backbone with four β-(1→6)-d-glucosyl side branching units every six residues. In addition, circular dichroism spectroscopic analysis revealed that the β-(1→3, 1→6)-glucan interacted with polyadenylic acid (poly(A)) chains in DMSO solution to form a complex similar to that obtained in the complexation of SPG/poly(A). This finding indicates that β-(1→3, 1→6)-glucan forms a triple-helical conformation in aqueous solution but exhibits a random coil structure in DMSO solution, which is similar to the behavior of SPG.

Systematic dynamic viscoelasticity measurements for chitin nanofibers prepared with various concentrations, disintegration times, acidities, and crystalline structures

Dynamic viscoelasticities were measured for chitin nanofiber (ChNF) dispersions prepared with various concentrations, disintegration times, acidities, and crystalline structures. The 0.05w/v% dispersions of pH neutral ChNFs continuously exhibited elastic behavior. The 0.05w/v% dispersions of acidified ChNFs, on the other hand, transitioned from a colloidal dispersion to a critical gel and then exhibited elastic behavior with increasing ChNF concentration. A double-logarithmic chart of the concentration vs. the storage modulus was prepared and indicated the fractal dimension and the nanostructure in the dispersion. The results determined that the neutral α- and β-ChNFs were dispersed but showed some remaining aggregations and that the acidified β-ChNFs were completely individualized. In addition, the α-chitin steadily disintegrated with increasing disintegration time, and the aspect ratio of the β-chitin decreased as a result of the exscessive disintegration. The storage moduli of the ChNFs were greater than those of chitin solutions, nanorods, and nanowhiskers with the same solids concentrations.

Utilization of Supercritical Fluid for Catalytic Thermochemical Conversions of Woody-Biomass Related Compounds

This chapter summarizes various valuable chemicals and gases that can be produced from woody biomass and related feedstock compounds using heterogeneous catalysts and supercritical fluid media (supercritical multiphase reaction). Merits and characteristics of the supercritical multiphase reaction are well demonstrated with two examples: (1) fuel gases production from lignin, a component of woody biomass, with supported ruthenium catalysts in supercritical water, and (2) hydrogenation of alkylphenols, fragments of lignin, with supported rhodium catalysts in supercritical carbon dioxide.

Two-dimensional NMR data of a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans and schizophyllan from Schizophyllum commune

This article contains two-dimensional (2D) NMR experimental data, obtained by the Bruker BioSpin 500 MHz NMR spectrometer (Germany) which can used for the determination of primary structures of schizophyllan from Schizophyllum commune (SPG) and a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans. Data include analyzed the 2D NMR spectra of these β-glucans, which are related to the subject of an article in Carbohydrate Polymers, entitled “NMR spectroscopic structural characterization of a water-soluble β-(1→3, 1→6)-glucan from A. pullulans” (Kono et al., 2017) [1]. Data can help to assign the 1H and 13C chemical shifts of the structurally complex polysaccharides.