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

Accepted 28 Jul 2014Non-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.ArticleRSC ADVANCES. 4(64):33651-33657 (2014)journal articl

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.ArticleCarbohydrate Polymers. 134:718-725 (2015)journal articl

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

Published online 20 June 2016The 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 3–10 nm, respectively.ArticleINTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES. 91:987-993 (2016)journal articl

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

Published online 11 Apr 2017We 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.ArticleINTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES. 102:358-366 (2017)journal articl

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

Published online 20 June 2016The 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 3–10 nm, respectively.ArticleINTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES. 91:987-993 (2016)journal articl

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.ArticleCarbohydrate Polymers. 134:718-725 (2015)journal articl

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

Published online 11 Apr 2017We 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.ArticleINTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES. 102:358-366 (2017)journal articl