Journal of applied glycoscience最新文献

Isoprimeverose [α-D-xylopyranosyl-(1→6)-D-glucose] is produced from xyloglucan using the cooperative action of glycoside hydrolases including isoprimeverose-producing oligoxyloglucan hydrolase and β-galactosidase in Aspergillus oryzae. This study investigated A. oryzae strains and culture conditions suitable for isoprimeverose production from xyloglucan. Each strain of A. oryzae had a different ability to degrade xyloglucans. When an A. oryzae strain with high xyloglucan-degradation activity was cultured in a medium containing partially degraded xyloglucan as the carbon source, the production of glycoside hydrolases that degrade xyloglucan into isoprimeverose was highly induced. Our procedure efficiently produced isoprimeverose from xyloglucan without any genetically modified microorganisms or purification of enzymes.

In this study, we developed a method to synthesize sophorose using three enzymes-sucrose phosphorylase from Leuconostoc mesenteroides, 1,2-β-oligoglucan phosphorylase from Enterococcus italicus, and exo β-1,2-glucooligosaccharide sophorohydrolase from Parabacteroides distasonis-in a one-pot reaction, employing inexpensive starting materials. After optimization, a reaction was carried out using 5 mM glucose, 250 mM sucrose, 10 mM inorganic phosphate, and enzyme concentrations of 5 µg/mL sucrose phosphorylase, 20 µg/mL 1,2-β-oligoglucan phosphorylase, and 50 µg/mL exo β-1,2-glucooligosaccharide sophorohydrolase at 30 °C for 48 h, yielding 108 mM sophorose. Following yeast treatment, sophorose was purified by size-exclusion chromatography with a final yield of 45 % based on the amount of sucrose used as the donor substrate.

Water sorption reduces the glass transition temperature (T _g) of amorphous carbohydrate powders due to water plasticization. Caking of amorphous powder occurs when T _g decreases below the storage temperature (T), that is, when the glass-to-rubber transition occurs. Although glass-to-rubber transition also occurs when T is greater than T _g, knowledge regarding the caking of amorphous powders induced by T elevation is limited. Thus, caking properties were investigated using amorphous carbohydrate powders with varying water activity (a _w) values prepared at 25 °C, stored at a higher temperature, and then returned to 25 °C (T-cycled samples) for storage. Maltodextrin and glucose mixtures at weight ratios of 0, 0.1, and 0.2 glucose were employed. The caking behavior of T-cycled powders with high a _w values was similar to that of a _w-cycled samples (dried powders were stored under various a _w conditions and then returned to the dry condition via vacuum-drying) reported previously. T-cycled powders with a low a _w value, by contrast, were resistant to caking even in the rubbery state. This suggests that water molecules support the progression of caking as the binder under high-a _w conditions. To analyze the hydration level at which water molecules begin to act as a binder for caking, determination of the multilayer adsorbed water content and multilayer adsorbed a _w values is proposed. The fracture stress increased with increases in T - T _g, depending on the sample. The binding effect of water also contributed to the formation of a harder cake.

Short linear maltodextrin (SLMD) was synthesized from starch via the combined action of branching and debranching enzymes. The number-average degree of polymerization and number-average chain length of SLMD were 8.49 ± 0.21 and 8.52 ± 0.60, respectively, indicating that it consists of linear chains. In gel permeation chromatography analyses, SLMD showed a single peak at a molecular weight of 1,200. SLMD consisted mainly of linear saccharides with a degree of polymerization of 6-12, without high molecular weight α-glucans or small malto-oligosaccharides. SLMD had a much higher blue value and a longer λmax compared with those of commercial dextrose equivalent (DE) 13 maltodextrin. While the DE 13 maltodextrin solution remained clear, an SLMD solution became turbid upon cooling, with the turbidity reversing upon heating. This interconversion was reproducible. SLMD absorbed moisture only to a limited extent, even under high relative humidity, and remained solid without noticeable viscousness. These results demonstrate the novelty and distinct properties of SLMD compared with those of other maltodextrins available on the market, implying its potential for various applications in the food industry.

Because of the complicated hierarchical structure of starch, starch retrogradation is usually evaluated by combining several structural analysis methods covering various spatial scales. However, structural analyses are typically performed individually, making correlating the structural changes at different spatial scales challenging. Therefore, this study used a simultaneous measurement system comprising small-angle neutron scattering (SANS)/Fourier-transform infrared (FTIR)-attenuated total reflection (ATR) to record multiple structural changes in potato starch during retrogradation. In the SANS patterns, the shoulder-like peak became more pronounced with time. The peak intensity, I _max, representing the amount of ordered semicrystalline structures, increased over time, revealing the orderly reassembly of starch on the nanoscale upon retrogradation. In the FTIR-ATR spectra, the ratio of absorptions (R _1042/1016) at 1,042 and 1,016 cm^-1, indicating the short-range ordered structure in starch, increased during retrogradation. Therefore, the double-helix structures were reformed during retrogradation. The rate constant of the kinetic change for R _1042/1016 was larger than for I _max; thus, changes in the short-range ordered structure of starch converged before the changes in the semicrystalline structure. These results suggest that the formation of double-helix structures of the amylopectin side chain and the structural change of its ordered arrangement could occur in stages during retrogradation.

D-Allulose 3-epimerase catalyzes C-3 epimerization between D-fructose and D-allulose was found in Arthrobacter globiformis strain M30. The enzyme gene was cloned, and its recombinant enzyme and the mutant variants were expressed in E. coli. Using the information of the sequence and model structure, we succeed in the improvement of melting temperature for the enzyme without significant loss of the enzyme activity by protein engineering method. The melting temperatures were increased by 2.7, 2.1, 3.7, 5.1, and 8.0 c[C for the mutants Glu75Pro, Arg137Lys, Ala200Lys, Ala270Lys, and Val237Ile, respectively. Each effect of the mutation was independent and additive. By integrating the above mutations, we constructed a thermostable mutant that exhibits a melting temperature 12 c[C higher than wild type, and remains stable at 65 c[C for 2 h. These highly stable properties suggest that the thermostable enzymes represent an ideal enzyme candidate for the industrial production of D-allulose.

β-Glucose 1-phosphate (βGlc1P) is a donor substrate in the synthesis of various α-glucosides by glycoside phosphorylases belonging to the glycoside hydrolase family 65. This study presents an efficient synthesis of βGlc1P combining enzymatic phosphorolysis of inexpensive maltose and baker's yeast fermentation to bias the equilibrium toward maltose phosphorolysis by removing released glucose. Mass production of βGlc1P was obtained in a 2 L reaction mixture initially containing 500 mM maltose and inorganic phosphate, with a yield of 76 %. βGlc1P was isolated from the reaction mixture by crystallization after electrodialysis to obtain 181 g of βGlc1P as a bis(cyclohexylammonium) salt.

Enzymatic hydrolysis of cellulosic biomass is a complex process involving many factors, including multiple enzymes, heterogeneous substrates, and multi-step enzyme reactions. Cellulase researchers have conventionally used a double-exponential equation to fit the experimental time course of product formation, but no theoretical basis for this has been established. Here we present a mechanism-based equation that fits well the progress curves of cellulase reaction, incorporating the concepts of non-productive and productive binding on the cellulose surface and processivity. The derived equation is double exponential. Our findings indicate that the reaction mechanism of cellulase itself can account for the double-exponential nature of the progress curve independently of other factors that may contribute, such as substrate heterogeneity and involvement of other enzymes.

The application of flour is determined by the composition of its starch and storage proteins. Previously isolated diploid waxy wheat is known to be amylose-free and possesses the same amylopectin structure as the wild-type. To reveal its characteristics, starch, protein, lipid, fiber, gluten, and allergen contents and rheological properties were analyzed and compared to its parental wild-type diploid wheat and commercially available hexaploid wheats. The results showed that the starch content of diploid waxy wheat was similar, but its protein, lipid, and fiber contents were higher than that of the wild-type. In addition, diploid waxy wheat produced high levels of gluten unlike its wild-type while its allergen level was similar to its wild-type. The storage modulus of diploid waxy wheat was significantly lower than that of other wheat lines at high temperatures. These results suggest that diploid waxy wheat holds different characteristics from hexaploid wheats for food processing.

The branched structure of amylose was probed using concanavalin A (ConA) lectin, which forms precipitable aggregates with highly branched glucans, such as glycogen and amylopectin. Rice (japonica cultivar) amylose was fractionated from de-fatted, gelatinized starch by precipitation with 1-butanol (BuOH) and purified by ultracentrifugation and repeated crystallization. The purified amylose still has short side chains, whose chain-length (CL) distribution resembles that of amylopectin. More than 96 wt% of the amylose was not precipitated with ConA and remained in the resultant supernatant. The amylose recovered from the supernatant exhibited essentially the same size distributions of molecules and the CL distributions of main and side chains as those of amylose without ConA precipitation. The molar % of branched molecules was slightly decreased by ConA precipitation (-ConA, 11.6; +ConA, 8.1). These results suggest that the side chains detected in BuOH-precipitable amylose preparation are essentially attributable to amylose itself. Also, the non-precipitable nature of the branched molecules of amylose by ConA supports our previous proposal that the organization of the short side chains on amylose molecules is quite different from that found in amylopectin, in which the short side chains are arranged in a cluster fashion, and the branched glucan interacts with ConA to form precipitable aggregates. A tiny amount of ConA-precipitable glucan was detected, but its CL distribution was inconsistent with the size distribution of the branched molecules. Even if the precipitable glucans were fragments of amylopectin, their contribution to the branches detected in amylose should be minor.