Preparation of hypoallergenic ovalbumin by high-temperature water treatment.

The high-temperature water treatment is one of the methods used to reduce the molecular weight of proteins. In this study, in order to establish a practical method for preparing hypoallergenic materials using the high-temperature water treatment, we investigated the effects of processing temperature on the antigenicity and allergenicity of a food allergen. Additionally, the foaming ability of the samples was also evaluated as a function desired in the food industry. We used ovalbumin as a model allergen. As a result, although there was no significant difference among the samples treated with different processing temperatures, all the antigens treated with high-temperature water showed a decrease in antigenicity and allergenicity. In addition, when ovalbumin was treated at a temperature of 130 °C or higher, there was a significant improvement in foaming properties. These findings indicate that high-temperature water treatment is a potential strategy for preparing practical hypoallergenic materials.

Environment-friendly utilization of squid pen with water: Production of ß-chitin nanofibers and peptides for lowering blood pressure.

Chitin, an abundant biopolymer on Earth, represents a resource for sustainable functional materials. However, traditional ß-chitin production methods involve alkaline treatment at approximately 90 °C for its separation from the protein, thus not suitable as a functional peptide, as it is mixed with an alkaline aqueous solution. This study examined the conversion of squid pen into solid ß-chitin and water-soluble peptides using only water at temperatures of 150-250 °C for 30-120 min. Solid ß-chitin was converted to its nanofiber form and the physicochemical properties of the ß-chitin nanofibers were almost the same as those produced by the traditional method. Because this method uses only water, the protein in the squid pen may also be a functional peptide for lowering blood pressure, by inhibiting the Angiotensin-1 converting enzyme. High-temperature water treatment is a promising environment-friendly technique for complete utilization of squid pen components, including ß-chitin and protein.

Effect of the degree of acetylation on the physicochemical properties of α-chitin nanofibers.

The effective utilization of abundant α-chitin resources for materials engineering applications requires methods for controlling the physicochemical properties of α-chitin nanofiber (NF) dispersions. Herein, the relationship between the degree of acetylation (DA) of α-chitin and the physicochemical properties of α-chitin nanofibers (α-ChNFs) was investigated. α-Chitin with different DAs was prepared by varying the deacetylation treatment time. These α-chitin samples were disintegrated into NFs using wet pulverization. The average width of the α-ChNFs decreased with decreasing DA. Furthermore, the transmittance and viscosity of the α-ChNF dispersions increased with decreasing DA. We successfully developed a simple model for estimating the average width of α-ChNFs with different DAs. These results indicate that the DA is an effective parameter for defining and controlling the physicochemical properties of α-ChNFs.

Non-catalytic conversion of chitin into Chromogen I in high-temperature water.

The non-catalytic conversion of chitin into N-acetyl-ᴅ-glucosamine (GlcNAc) derivatives such as 2-acetamido-2,3-dideoxy-ᴅ-erythro-hex-2-enofuranose (Chromogen I) was investigated in high-temperature water at 290-390 °C and 25 MPa with a reaction time of 0-180 min. High-temperature water treatment is a promising method for chitin conversion as it does not require the use of any additional organic solvents or ionic liquids. A semi-batch reactor was developed to control the reaction temperature and time. It was found that the chitin powder could be converted into a water-soluble fraction in ~90% yield, with Chromogen I being obtained in a maximum yield of 2.6%. Furthermore, a kinetic model was developed to estimate the reaction rate for the conversion of the chitin powder to the water-soluble fraction.

Preparation of ß-chitin nanofiber aerogels by lyophilization.

In this study, chitin nanofiber dispersions prepared in neutral and acidic pH conditions were lyophilized to produce aerogels. The effects of the freezing speed of the nanofiber dispersions and the dispersibility of the chitin nanofiber were studied. The characteristics of the aerogels were studied using scanning electron microscopy, relative surface area measurements, and compression tests. The repulsion forces of the chitin nanofiber in acidic conditions were effective in the formation of a more uniform microstructure during water solidification, resulting in aerogels with a high mechanical strength. The aerogel made from the chitin nanofiber dispersion prepared in neutral conditions was influenced by ice crystal growth during freezing, resulting in a nonuniform structure. In contrast, the surface area of the aerogel in neutral conditions interestingly remained unchanged compared to that of the original powder, which was due to the morphological transformation.

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 ß-ChNFs were dispersed but showed some remaining aggregations and that the acidified ß-ChNFs were completely individualized. In addition, the α-chitin steadily disintegrated with increasing disintegration time, and the aspect ratio of the ß-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.

Self-Sustaining Cellulose Nanofiber Hydrogel Produced by Hydrothermal Gelation without Additives.

We prepared a self-sustaining hydrogel from 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNs) via hydrothermal treatment at 160 °C. The self-sustaining hydrogels could be obtained at less than 1 wt % TOCNs without any additives. Brownish hydrogels obtained after the hydrothermal treatment could be rendered transparent by immersing them in distilled water at 5 °C. The compressive modulus of the hydrogel increased with increasing heating time. X-ray diffraction studies reveal that the crystal structure of the internal layers of the TOCNs remained intact after the hydrothermal treatment and depigmentation. The hydrothermal treatment caused the hydrolysis of molecules, especially the glucuronate units, from the external layer of TOCN. The elimination of the glucuronate units decreased the net negative surface charge of the TOCNs, resulting in their aggregation into a three-dimensional network structure owing to the predominance of attractive forces. Such additive-free hydrogels that can be shaped into diverse forms are promising for medical applications.

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

An unambiguous structural characterization of the water-soluble Aureobasidium pullulans ß-(1→3, 1→6)-glucan is yet to be achieved, although this ß-(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 ß-(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 ß-(1→3, 1→6)-glucan revealed that the structural units are a ß-(1→3)-d-glucan backbone with four ß-(1→6)-d-glucosyl side branching units every six residues. In addition, circular dichroism spectroscopic analysis revealed that the ß-(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 ß-(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.

Effect of acidity on the physicochemical properties of α- and ß-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 ß-ChNFs was compared. The transmittance and viscosity of the ß-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 ß-chitin than α-chitin. In addition, the effect of the acid species on the transmittance of ß-ChNFs was investigated. The transmittance of ß-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.

Two-dimensional NMR data of a water-soluble ß-(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 ß-(1→3, 1→6)-glucan from Aureobasidium pullulans. Data include analyzed the 2D NMR spectra of these ß-glucans, which are related to the subject of an article in Carbohydrate Polymers, entitled "NMR spectroscopic structural characterization of a water-soluble ß-(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.

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

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

Effect of sub- and supercritical water treatments on the physicochemical properties of crab shell chitin and its enzymatic degradation.

This study examined the effects of sub- and supercritical water pretreatments on the physicochemical properties of crab shell α-chitin and its enzymatic degradation to obtain N,N'-diacetylchitobiose (GlcNAc)2. Following sub- and supercritical water pretreatments, the protein in the crab shell was removed and the residue of crab shell contained α-chitin and CaCO3. Prolonged pretreatment led to α-chitin decomposition. The reaction of pure α-chitin in sub- and supercritical water pretreatments was investigated separately; we observed lower mean molecular weight and weaker hydrogen bonds compared with untreated α-chitin. (GlcNAc)2 yields from enzymatic degradation of subcritical (350 °C, 7 min) and supercritical water (400 °C, 2.5 min) pretreated crab shell were 8% and 6%, compared with 0% without any pretreatment. This study shows that sub- and supercritical water pretreatments of crab shell provide to an alternative method to the use of acid and base for decalcification and deproteinization of crab shell required for (GlcNAc)2 production.

Effects of supercritical water and mechanochemical grinding treatments on physicochemical properties of chitin.

This study examined the effects of a combined pretreatment with supercritical water and mechanochemical grinding with a ball mill on the physicochemical properties of chitin and its enzymatic degradation. Following pretreatment with a combination of supercritical water and grinding, chitin had a lower mean molecular weight, a lower crystallinity index, a lower crystallite size, greater d-spacing, weaker hydrogen bonds, and the amide group was more exposed compared with untreated chitin. These properties increased the hydrophilicity of the chitin and enhanced its enzymatic degradation. The N,N'-diacetylchitobiose (GlcNAc)(2) yield after enzymatic degradation of chitin following pretreatment with supercritical water (400 °C, 1 min) and grinding (800 rpm, 10 min) was 93%, compared with 5% without any treatment, 37% with supercritical water pretreatment alone (400 °C, 1 min), and 60% with grinding alone (800 rpm, 30 min).

Amination of n-hexanol in supercritical water.

The amination of 1-n-hexanol followed by amidation was carried out in supercritical water at 380, 400, and 420 degrees C and water densities of 0.1, 0.3, and 0.5 g/cm3. The replacement of the hydroxyl group with the amino group was found to occur in 1-n-hexanol using ammonium acetate in supercritical water without the addition of a metal or an acid catalyst. The yield of the final product, N-n-hexylacetamide, increased by increasing the reaction temperature, water density, and the amount of ammonium acetate. The yield and the selectivity of N-n-hexylacetamide were 78.5% and 87.5%, respectively, in supercritical water at 400 degrees C, 0.5 g/cm3, for 10 min.