Journal of applied glycoscience最新文献

3-Keto-levoglucosan (3ketoLG) has been postulated to be the product of a reaction catalyzed by levoglucosan dehydrogenase (LGDH), a bacterial enzyme involved in the metabolism of levoglucosan (LG). To investigate the LG metabolic pathway catalyzed by LGDH, 3ketoLG is needed. However, 3ketoLG has not been successfully isolated from the LGDH reaction. This study investigated the ability of pyranose oxidase to convert LG into 3ketoLG by oxidizing the C3 hydroxyl group. During the oxidation of LG, 3ketoLG was spontaneously crystallized in the reaction mixture. Starting with 500 mM LG, the isolation yield of 3ketoLG was 80 %. Nuclear magnetic resonance analyses revealed that a part of 3ketoLG dimerized in aqueous solution, explaining its poor solubility. Even under normal conditions, 3ketoLG was unstable in aqueous solution, with a half-life of 16 h at pH 7.0 and 30 °C. The decomposition proceeded through β-elimination of the C-O bonds at both C1 and C5, as evidenced by decomposition products. This instability explains the difficulty in obtaining 3ketoLG via the LGDH reaction.

A GH67 α-glucuronidase gene derived from Bacillus halodurans C-125 was expressed in E. coli to obtain a recombinant enzyme (BhGlcA67). Using the purified enzyme, the enzymatic properties and substrate specificities of the enzyme were investigated. BhGlcA67 showed maximum activity at pH 5.4 and 45 °C. When BhGlcA67 was incubated with birchwood, oat spelts, and cotton seed xylan, the enzyme did not release any glucuronic acid or 4-O-methyl-glucuronic acid from these substrates. BhGlcA67 acted only on 4-O-methyl-α-D-glucuronopyranosyl-(1→2)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranose (MeGlcA³Xyl₃), which has a glucuronic acid side chain with a 4-O-methyl group located at its non-reducing end, but did not on β-D-xylopyranosyl-(1→4)-[4-O-methyl-α-D-glucuronopyranosyl-(l→2)]-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylop- yranose (MeGlcA³Xyl₄) and α-D-glucuronopyranosyl-(l→2)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-xylopyranose (GlcA³Xyl₃). The environment for recognizing the 4-O-methyl group of glucuronic acid was observed in all the crystal structures of reported GH67 glucuronidases, and the amino acids for discriminating the 4-O-methyl group of glucuronic acid were widely conserved in the primary sequences of the GH67 family, suggesting that the 4-O-methyl group is critical for the activities of the GH67 family.

A fermented beverage of plant extracts (Super Ohtaka^®) was prepared from about 50 kinds of fruits and vegetables. This natural fermentation was performed by yeast (Zygosaccharomyces spp. and Pichia spp.) and lactic acid bacteria (Leuconostoc spp.) and resulted in the production of a novel fructopyranose-containing saccharide, which was subsequently isolated using carbon-Celite column chromatography and preparative-HPLC. The structure of the saccharide was determined using MALDI-TOF MS and NMR, and the saccharide was identified as β-D-fructopyranosyl-(2→6)-β-D-fructofuranosyl-(2↔1)-α-D-glucopyranoside. This is the first description of this novel saccharide and its isolation from a natural source.

The aim of this study was to clarify the change in the powder properties of rice flour depending on the milling process. Rice flour samples, which have gradual mechanical shock properties, were prepared using different milling methods. Furthermore, the correlation between the starch damage, owing to mechanical shock, and powder properties of rice flour was investigated. The particle size was changed gradually through each milling process; however, the change did not clearly correlate with starch damage. The results of the X-ray diffraction (XRD) pattern of nongelatinized samples showed the typical A-type structure of starch. The crystal structure of starch in rice flour may change to a disorder state with the progress of milling; thus, in this study, instead of crystallinity, we considered the disorder index (DI) calculated from the XRD intensity of samples. Relationship between DI and starch damage was confirmed with R ² = 0.923. Therefore, the mechanical shock caused by the milling process contributes to the crystal state of starch. The parameter q _m calculated from the Guggenheim-Anderson-de Boer (GAB) equation of each sample corresponded to the DI. This result suggested that the sorption site of rice flour decreased, and a positive correlation was observed between the parameter K and DI. Thus, the interaction between the rice flour and water molecules weakened because of the mechanical shock. In addition, the use of a SEM image supports the insight that the change in parameter K may reflect the structural change in the solid phase. These results demonstrated that the change in powder properties of rice flour caused by mechanical shock of the milling could evaluate quantitatively.

Salmon cartilage proteoglycan fractions have recently gained favor as ingredients of functional food and cosmetics. An optimal hot water method to extract proteoglycan from salmon cartilage has recently been developed. The extracted cartilage includes hyaluronan and collagen in addition to proteoglycan as counterparts that interact with each other. In this study, biochemical analyses and atomic force microscopical analysis revealed global molecular images of proteoglycan in the hot water extract. More than seventy percent of proteoglycans in this extract maintained their whole native structures. Hyaluronan purified from the hot water extract showed a distribution with high molecular weight similar to hyaluronan considered to be native hyaluronan in cartilage. The current data is evidence of the quality of this hot water cartilage extract.

We previously reported that sensitivity to Congo Red (CR) or Lysing Enzymes (LE) is affected by the loss of cell-wall α-1,3-glucan (AG) in Aspergillus nidulans. We found that the amount of CR adsorbed to AG was significantly less than the amount adsorbed to β-1,3-glucan (BG) or chitin, suggesting that loss of cell-wall AG would increase exposure of BG on the cell surface, and thereby increase the sensitivity to CR. Generally, fungal BGs are known as biological response modifiers because of their recognition by Dectin-1 receptors in human immune systems. Therefore, isolation of AG-deficient mutants in Aspergillus oryzae has been used in the Japanese fermentation industry to create strains with increased ability to promote immune responses. Here, we aimed to isolate AG-deficient strains by mutagenizing A. oryzae conidia with chemical mutagens. Based on the increased sensitivity to CR in AG-deficient strains of A. nidulans and A. oryzae, we established a screening method for isolation of AG-deficient strains. Several candidate AG-deficient mutants of A. oryzae were isolated using the screening method; these strains showed increased sensitivity to CR and/or LE. Cytokine production was increased in the dendritic cells co-incubated with germinated conidia of the AG-deficient mutants. Furthermore, according to a Dectin-1 NFAT (nuclear factor of activator T cells)-GFP (green fluorescent protein) reporter assay, Dectin-1 response levels in the AG-deficient mutants were higher than those in wild-type A. oryzae. These results suggest that we successfully isolated AG-deficient mutants of A. oryzae with immunostimulatory effects.

In 2014, potato production in China amounted to 96 million tons, which was the highest in the world. As one of the most important nutritional foods in the world, potato is rich in starch, dietary fiber, vitamins, minerals, etc. Potatoes stand barren environment, drought, saline, and alkaline environment, and cold weather, with a short growing season. These features make them the best rain-fed crops suitable for production even when the annual rainfall is below 400 mm. In 2013, the Chinese Ministry of Agriculture suggested a potato staple food strategy using potatoes to make Chinese traditional staple foods such as steamed bread, noodles, etc. Our research group carried out a study on processing technology of potato staple food, especially fermented staple food. Some new processing technologies of potato staple food have been investigated and developed. The aim of this paper is to give an overview of the possible effects of adding potato flour in the dough and of the microstructure characteristics, technological parameters, total polyphenol content, and antioxidant activity of staple foods. We also systematically describe the processing technology of potato staple foods, which may be of great importance in promoting further expansion of the potato-processing industry and increasing the economic benefit of the companies.

Potatoes are generally regarded as high glycemic index (GI) foods. Resistant starch (RS) comprises the starch fraction that is not absorbed in the small intestine, thus controlling the glucose level and improving the intestinal environment. In this study, an analysis of the formation of RS of potato starch samples under different acetic acid-thermal treatment conditions was conducted. Additionally, the relationship between the rates of starch digestion, estimated GI (eGI), and the RS content was evaluated by employing in vitro enzymatic models. Compared with control samples, the RS content in the cold-stored samples after acid-boiling was higher, whereas that of samples after heating at 120 °C with acetic acid was decreased. The eGI was negatively correlated with the RS content in potatoes. Cold store after acid-boiling was effective in increasing the RS content. Furthermore, low eGI values may have resulted from higher levels of RS in potatoes.

We report production of the functional disaccharide gentiobiose β-D-Glcp-(1→6)-D-Glc by a hydrolysis reaction of hydrothermally treated Aureobasidium pullulans β-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 β-1,3-1,6-glucan was lower than that from A. pullulans β-1,3-1,6-glucan.

We prepared and characterized amylose nanogels containing ionic polysaccharides which we used were 4-O-methyl-D-glucurono-D-xylan (GX), alginate, xanthan, and chitosan. Gelation under a shear force followed by a wet pulverization leads to the formation of hybrid nanogels. The resultant nanogels were characterized by particle size analysis, zeta-potential measurement and atomic force microscopy (AFM). Wet pulverization under a pressure of 200 MPa reduced the particle size of the gels from 20-26 μm to 240-670 nm. Zeta potential measurement showed that the ionic polysaccharides increased surface charges of the amylose gels. AFM observations showed the network consisting of submicron size amylose-polysaccharide nano fibrils. The fibrils containing GX were dispersed uniformly, while those containing only amylose were partly aggregated.