Development of an oligosaccharide library to characterise the structural variation in glucuronoarabinoxylan in the cell walls of vegetative tissues in grasses.

BACKGROUND: Grass glucuronoarabinoxylan (GAX) substitutions can inhibit enzymatic degradation and are involved in the interaction of xylan with cell wall cellulose and lignin, factors which contribute to the recalcitrance of biomass to saccharification. Therefore, identification of xylan characteristics central to biomass biorefining improvement is essential. However, the task of assessing biomass quality is complicated and is often hindered by the lack of a reference for a given crop. RESULTS: In this study, we created a reference library, expressed in glucose units, of Miscanthus sinensis GAX stem and leaf oligosaccharides, using DNA sequencer-Assisted Saccharide analysis in high throughput (DASH), supported by liquid chromatography (LC), nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Our analysis of a number of grass species highlighted variations in substitution type and frequency of stem and leaf GAX. In miscanthus, for example, the β-Xylp-(1 → 2)-α-Araf-(1 → 3) side chain is more abundant in leaf than stem. CONCLUSIONS: The reference library allows fast identification and comparison of GAX structures from different plants and tissues. Ultimately, this reference library can be used in directing biomass selection and improving biorefining

Development and application of a high throughput carbohydrate profiling technique for analyzing plant cell wall polysaccharides and carbohydrate active enzymes

BACKGROUND: Plant cell wall polysaccharide composition varies substantially between species, organs and genotypes. Knowledge of the structure and composition of these polysaccharides, accompanied by a suite of well characterised glycosyl hydrolases will be important for the success of lignocellulosic biofuels. Current methods used to characterise enzymatically released plant oligosaccharides are relatively slow. RESULTS: A method and software was developed allowing the use of a DNA sequencer to profile oligosaccharides derived from plant cell wall polysaccharides (DNA sequencer-Assisted Saccharide analysis in High throughput, DASH). An ABI 3730xl, which can analyse 96 samples simultaneously by capillary electrophoresis, was used to separate fluorophore derivatised reducing mono- and oligo-saccharides from plant cell walls. Using electrophoresis mobility markers, oligosaccharide mobilities were standardised between experiments to enable reproducible oligosaccharide identification. These mobility markers can be flexibly designed to span the mobilities of oligosaccharides under investigation, and they have a fluorescence emission that is distinct from that of the saccharide labelling. Methods for relative and absolute quantitation of oligosaccharides are described. Analysis of a large number of samples is facilitated by the DASHboard software which was developed in parallel. Use of this method was exemplified by comparing xylan structure and content in Arabidopsis thaliana mutants affected in xylan synthesis. The product profiles of specific xylanases were also compared in order to identify enzymes with unusual oligosaccharide products. CONCLUSIONS: The DASH method and DASHboard software can be used to carry out large-scale analyses of the compositional variation of plant cell walls and biomass, to compare plants with mutations in plant cell wall synthesis pathways, and to characterise novel carbohydrate active enzymes

Assessment of Structure and Properties Homogeneity after Repairing of a Nickel-Based Superalloy Product by the Electron Beam Additive Technology

Repairing damaged products made of nickel-based superalloys is an urgent task because replacing them with new products is a costly and time-consuming process. The present work considers the method of electron-beam additive manufacturing as an approach to the repair process. First of all, the initial product was produced by layer-by-layer deposition. Hereon, a part of the surface was removed, and then several more layers were deposited. Thus, three areas were considered in the work: initial, transitional, and repaired areas. Each of the formed regions was defect-free. It was found that the transition region was difficult to identify since it did not differ in structural-phase composition from the initial and repaired regions. It is shown that the complex thermal history consisting of periodic thermal exposure and repeated melting of the newly crystallized layers does not lead to the formation of defects and undesirable phases. Moreover, in all three regions, there is a redistribution of the chemical element content of the γ′ and γ phases towards an increase in the mismatch of their lattice parameters. The mechanical properties of the transition and repaired regions are not significantly different from the initial area

Regularities of Friction Stir Processing Hardening of Aluminum Alloy Products Made by Wire-Feed Electron Beam Additive Manufacturing

Friction stir processing of additive workpieces in the sample growth direction (the vertical direction) and the layer deposition direction (the horizontal one) was carried out. The hardening regularities of aluminum-silicon alloy A04130 and aluminum-magnesium alloy AA5056 manufactured by electron beam additive technology were studied. For each material, 1 to 4 subsequent tool passes were performed in both cases. It was found that the formation of the stir zone macro-structure does not significantly change with the processing direction relative to the layer deposition direction in additive manufacturing. The average grain size in the stir zone after the fourth pass for AA5056 alloy in the horizontal direction was 2.5 ± 0.8 μm, for the vertical one, 1.6 ± 0.5 μm. While for the alloy A04130, the grain size was 2.6 ± 1.0 μm and 1.8 ± 0.7 for the horizontal and vertical directions, respectively. The fine-grained metal of the stir zone for each alloy in different directions had higher microhardness values than the base metal. The tensile strength of the processed metal was significantly higher than that of the additively manufactured material of the corresponding alloy. The number of tool passes along the processing line is different for the two selected alloys. The second, third and fourth passes have the most significant effect on the mechanical properties of the aluminum-magnesium alloy