Preparation and characterization of carboxymethylated Aureobasidium pullulans ß-(1 → 3, 1 → 6)-glucan and its in vitro antioxidant activity.

Aureobasidium pullulans ß-(1 â†’ 3, 1 â†’ 6)-glucan (APG) has a high degree of ß-(1 â†’ 6)-glucosyl branching and a regular triple helical structure similar to that of schizophyllan. In this study, APG was carboxymethylated to different degrees of substitution (DS = 0.51, 1.0, and 2.0, denoted CMAPG 1-3, respectively) using a heterogeneous reaction. With increasing DS, the triple-helix structure drastically decreased and converted to a random coil structure in CMAPG 3. Further, aqueous solutions of CMAPG changed from pseudoplastic fluids to perfect Newtonian liquids with increasing DS, indicating that the intra- and intermolecular hydrogen bonds had been cleaved by the substituents to form a random coil structure. In addition, APG and CMAPG solutions exhibited scavenging ability against hydroxyl, organic, and sulfate radicals. It was also found that the carboxymethylation of APG drastically enhanced the organic radical scavenging ability. On the basis of the relationship between the DS and radical scavenging ability of the CMAPG samples, we believe hydroxyl and organic radicals were preferably scavenged by the donation of hydrogen atoms from the glucose rings and the methylene moieties of the carboxymethyl groups, respectively. Considering the obtained results, CMAPG and APG are expected to have applications in pharmaceuticals, functional foods, and cosmetics as antioxidant polysaccharides.

Solid-state relaxation NMR dataset for a water-soluble ß-(1→3, 1→6)-glucan from Aureobasidium pullulans and schizophyllan from Schizophyllum commune.

We report the solid-state nuclear magnetic resonance (NMR) relaxation dataset for a triple helix and a random structure of water-soluble Aureobasidium pullulans ß-(1→3, 1→6)-d-glucan (APG) and those of schizophyllan from Schizophyllum commune (SPG), obtained by the Bruker BioSpin 500 MHz NMR spectrometer. These data include solid-state proton spin-lattice relaxation in the rotating frame (T 1ρH) and 13C spin-lattice relaxation (T 1C) of these two ß-(1→3, 1→6)-glucans, which are related to the subject of article in International Journal of Biological Macromolecules, entitled "Characterization of the secondary structure and order-disorder transition of a ß-(1→3, 1→6)-glucan from Aureobasidium pullulans" [1]. Data can help to investigate the structural characterization of the structural polysaccharides.

Characterization of the secondary structure and order-disorder transition of a ß-(1 → 3, 1 → 6)-glucan from Aureobasidium pullulans.

This study revealed the secondary structures of the water-soluble Aureobasidium pullulans ß-(1 â†’ 3, 1 â†’ 6)-d-glucan (APG) whose primary structural unit is a ß-(1 â†’ 3)-d-glucan backbone with four ß-(1 â†’ 6)-d-glucosyl branching units every six residues. Solid-state NMR spectroscopy, X-ray diffractometry (XRD), and small-angle X-ray scattering (SAXS) experiments involving samples prepared from lyophilized APG showed that APG forms a triple helix in H2O and a random structure in DMSO. In addition, it was revealed that the transformation from the triple helix of APG to the random structure occurs reversibly, and that the triple helix is recovered from the random structure in DMSO/H2O mixtures containing more than 30% H2O. Solid-state NMR and diffraction studies revealed that the triple helix of APG is more stable than that of schizophyllan (SPG) whose structure comprises a ß-(1 â†’ 3)-d-glucan backbone with one ß-(1 â†’ 6)-d-branching unit every three residues. The APG helical pitch is 1.82 nm, which is about 10% longer than that of the triple helix of SPG. These findings show that the ß-(1 â†’ 6) side-chain frequency strongly affects the stability and helical pitch of a ß-(1 â†’ 3, 1 â†’ 6)-d-glucan.

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.

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.

Production of Gentiobiose from Hydrothermally Treated Aureobasidium pullulans ß-1,3-1,6-Glucan.

We report production of the functional disaccharide gentiobiose ß-D-Glcp-(1→6)-D-Glc by a hydrolysis reaction of hydrothermally treated Aureobasidium pullulans ß-1,3-1,6-glucan as the substrate and Kitalase as the enzyme. Gentiobiose was produced over the pH range 4-6 and the concentration of gentiobiose produced decreased above pH 7. The maximum value of gentiobiose production was unaffected by the enzyme concentration. The maximum concentration of gentiobiose produced was dependent on the substrate concentration whereas the maximum ratio of gentiobiose to glucose was not. The production of gentiobiose from yeast ß-1,3-1,6-glucan was lower than that from A. pullulans ß-1,3-1,6-glucan.

Production of the Functional Trisaccharide 1-Kestose from Cane Sugar Molasses Using Aspergillus japonicus ß-Fructofuranosidase.

We report the production of the functional trisaccharide 1-kestose, O-ß-D-fructofuranosyl-(2→1)-ß-D-fructofuranosyl α-D-glucopyranoside, by ß-fructofuranosidase from Aspergillus japonicus using sugar cane molasses as substrate. Sucrose in cane sugar molasses acted as a fructosyl donor and acceptor for the enzyme. The tetrasaccharide nystose, O-ß-D-fructofuranosyl-(2→1)-ß-D-fructofuranosyl-(2→1)-ß-D-fructofuranosyl α-D-glucopyranoside, was produced from 1-kestose. Cane sugar molasses mixed with water provided a better substrate solution for ß-fructofuranosidase compared to undiluted molasses due to the high concentration of product inhibitors such as glucose and fructose in molasses. The maximum concentration of 1-kestose obtained was 84.9 mg/ml and the maximum production efficiency was 32.3% after 24 h reaction at 40 °C. The maximum efficiency of combined fructo-oligosaccharide (1-kestose and nystose) production was 40.6%. 1-Kestose was therefore produced via a fructosyl-transfer reaction catalyzed by ß-fructofuranosidase from A. japonicus.

Characterization and enzymatic hydrolysis of hydrothermally treated ß-1,3-1,6-glucan from Aureobasidium pullulans.

The chemical structure of hydrothermally treated ß-1,3-1,6-glucan from Aureobasidium pullulans was characterized using techniques such as gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR). The chemical shifts of anomeric carbons observed in the 13C-NMR spectra suggested the presence of single flexible chains of polysaccharide in the sample. ß-1,3-1,6-Glucan from A. pullulans became water-soluble, with an average molecular weight of 128,000 Da after hydrothermal treatment, and the solubility in water was approximately 10% (w/w). Sample (3% w/v) was completely hydrolyzed to glucose by enzymatic reaction with Lysing enzymes from Trichoderma harzianum. Gentiobiose (Glcß1 â†’ 6Glc) and glucose were released as products during the reaction, and the maximum yield of gentiobiose was approximately 70% (w/w). The molar ratio of gentiobiose to glucose after 1 h reaction suggested that the sample is likely highly branched. Sample (3% w/v) was also hydrolyzed to glucose by Uskizyme from Trichoderma sp., indicating that it is very sensitive to enzymatic hydrolysis.