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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Separation of thorium (IV) from lanthanide concentrate (LC) and water leach purification (WLP) residue

Thorium (IV) content in industrial residue produced from rare earth elements production industry is one of the challenges to Malaysian environment. Separation of thorium from the lanthanide concentrate (LC) and Water Leach Purification (WLP) residue from rare earth elements production plant is described. Both materials have been tested by sulphuric acid and alkaline digestions. Th concentrations in LC and WLP were determined to be 1289.7 ± 129 and 1952.9±17.6 ppm respectively. The results of separation show that the recovery of Th separation from rare earth in LC after concentrated sulphuric acid dissolution and reduction of acidity to precipitate Th was found 1.76-1.20% whereas Th recovery from WLP was less than 4% after concentrated acids and alkali digestion processes. Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) was used to determine Th concentrations in aqueous phase during separation stages. This study indicated that thorium maybe exists in refractory and insoluble form which is difficult to separate by these processes and stays in WLP residue as naturally occurring radioactive material (NORM)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Assessment of heavy metals in seawater and fish tissues at Pulau Indah, Selangor, Malaysia

This study focuses on the levels of heavy metals in seawater and selected fish tissue at Pulau Indah, Selangor, Malaysia. Pulau Indah primarily contains Westport (Malaysia’s major port), and a host of full scales factories. Therefore, it is important to monitor the levels of pollution in this water body and the aquatic organisms in the long term effects, due to the human activities in this area. Water samples in this study were taken from 8 locations along the coastal area. The water samples were collected using water sampler and sampling locations were determined using a Global Positioning system (GPS). Similarly, in situ water quality parameters including temperature, dissolve oxygen (DO), salinity, total suspended solid (TSS), pH and turbidity were measured by using portable multi probes meter. Then, the samples were acidified until pH 2 and filtered. Fish samples were purchased from local fisherman along the Pulau Indah coastal area and samples were digested using concentrated nitric acid in wet digestion method. The levels of selected heavy metals in four species of fish and seawater from Pulau Indah coastal area were determined using Inductive Coupled Plasma Mass Spectrometer (ICPMS) after dilution to the samples. In general, the quality of water at Pulau Indah is lower than Malaysia Marine Water Quality Standard except for few locations were higher than the maximum permissible levels. The concentration of heavy metals which are lead (Pb), copper (Cu), zinc (Zn) and uranium (U) in water samples are in the range of 0.36-5.43 µg/L, 75.20-621.58 µg/L, 11.92-30.52 µg/L, and 4.00-4.65 µg/L respectively. While the results of the four selected fish showed the following order of abundance Zn> U> Cu> Pb. Transfer factor (TF) of heavy metals in fish tissue of selected fish species from the water was discussed. However, the observed metal concentration in the sample tissue did not exceed the allowable limit of Malaysian Food Act (1983) and Regulation (1985). Therefore, it is safe for human consumption. Moreover, the pollution levels of these heavy metals were also compared with other studies. This present study can also be used to evaluate the safety dose uptake level of marine biota as well as to monitor environmental health.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Global Shape and Ligand Binding Efficiency of the HIV-1-neutralizing Antibodies Differ from Those of Antibodies That Cannot Neutralize HIV-1

Asymmetric disposition of Fab arms in the structures solved for the broadly neutralizing monoclonal antibody (nmAb) IgG1 b12 raised the question of whether the unusual shape observed for b12 is common for all IgG1 mAbs or if there is a difference in the overall shape of nmAbs versus non-nmAbs. In this paper, we compared small angle x-ray scattering (SAXS) data-based models and limited proteolysis profiles of some IgG1 mAbs known to be having and lacking HIV-1 neutralizing potency. In non-nmAbs, the Fab arms were found to be symmetrically disposed in space relative to central Fc, but in most nmAbs, the Fab arms were asymmetrically disposed, as seen for IgG1 b12. The only exceptions were 2G12 and 4E10, where both Fab arms were closed above Fc, suggesting some Fab-Fc and/or Fab-Fab interaction in the nmAbs that constrained extension of the Fab-Fc linker. Interestingly, these observations were correlated with differential proteolysis profiles of the mAbs by papain. Under conditions when papain could cut both Fab arms of non-nmAbs, only one Fab arm could be removed from neutralizing ones (except for 2G12 and 4E10). Chromatography and small angle x-ray scattering results of papain-digested products revealed that 1) the Fab-Fc or Fab-Fab interactions in unliganded mAbs are retained in digested products, and 2) whereas anti-gp120 non-nmAbs could bind two gp120 molecules, nmAbs could bind only one gp120. Finally, additional experiments showed that except for 2G12 and 4E10, unopen shapes of nmAbs remain uninfluenced by ionic strength but can be reversibly opened by low pH of buffer accompanied by loss of ligand binding ability.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Structural and Biochemical Characterization of a Novel Aminopeptidase from Human Intestine

N-acetylated α-linked acidic dipeptidase-like protein (NAALADase L), encoded by the NAALADL1 gene, is a close homolog of glutamate carboxypeptidase II, a metallopeptidase that has been intensively studied as a target for imaging and therapy of solid malignancies and neuropathologies. However, neither the physiological functions nor structural features of NAALADase L are known at present. In this paper, we report a thorough characterization of the protein product of the human NAALADL1 gene, including heterologous overexpression and purification, structural and biochemical characterization, and analysis of its expression profile. By solving the NAALADase L x-ray structure, we provide the first experimental evidence that it is a zinc-dependent metallopeptidase with a catalytic mechanism similar to that of glutamate carboxypeptidase II yet distinct substrate specificity. A proteome-based assay revealed that the NAALADL1 gene product possesses previously unrecognized aminopeptidase activity but no carboxy- or endopeptidase activity. These findings were corroborated by site-directed mutagenesis and identification of bestatin as a potent inhibitor of the enzyme. Analysis of NAALADL1 gene expression at both the mRNA and protein levels revealed the small intestine as the major site of protein expression and points toward extensive alternative splicing of the NAALADL1 gene transcript. Taken together, our data imply that the NAALADL1 gene product's primary physiological function is associated with the final stages of protein/peptide digestion and absorption in the human digestive system. Finally, based on these results, we suggest a new name for this enzyme: human ileal aminopeptidase (HILAP).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Molecular basis of structural make-up of feeds in relation to nutrient absorption in ruminants, revealed with advanced molecular spectroscopy: A review on techniques and models

Progress in ruminant feed research is no more feasible only based on wet chemical analysis, which is merely able to provide information on chemical composition of feeds regardless of their digestive features and nutritive value in ruminants. Studying internal structural make-up of functional groups/feed nutrients is often vital for understanding the digestive behaviors and nutritive values of feeds in ruminant because the intrinsic structure of feed nutrients is more related to its overall absorption. In this article, the detail information on the recent developments in molecular spectroscopic techniques to reveal microstructural information of feed nutrients and the use of nutrition models in regards to ruminant feed research was reviewed. The emphasis of this review was on (1) the technological progress in the use of molecular spectroscopic techniques in ruminant feed research; (2) revealing spectral analysis of functional groups of biomolecules/feed nutrients; (3) the use of advanced nutrition models for better prediction of nutrient availability in ruminant systems; and (4) the application of these molecular techniques and combination of nutrient models in cereals, co-products and pulse crop research. The information described in this article will promote better insight in the progress of research on molecular structural make-up of feed nutrients in ruminants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Energy and nutrient recovery from municipal and industrial waste and wastewater—a perspective

This publication highlights the latest advancements in the field of energy and nutrient recovery from organics rich municipal and industrial waste and wastewater. Energy and carbon rich waste streams are multifaceted, including municipal solid waste, industrial waste, agricultural by-products and residues, beached or residual seaweed biomass from post-harvest processing, and food waste, and are valuable resources to overcome current limitations with sustainable feedstock supply chains for biorefining approaches. The emphasis will be on the most recent scientific progress in the area, including the development of new and innovative technologies, such as microbial processes and the role of biofilms for the degradation of organic pollutants in wastewater, as well as the production of biofuels and value-added products from organic waste and wastewater streams. The carboxylate platform, which employs microbiomes to produce mixed carboxylic acids through methane-arrested anaerobic digestion, is the focus as a new conversion technology. Nutrient recycling from conventional waste streams such as wastewater and digestate, and the energetic valorization of such streams will also be discussed. The selected technologies significantly contribute to advanced waste and wastewater treatment and support the recovery and utilization of carboxylic acids as the basis to produce many useful and valuable products, including food and feed preservatives, human and animal health supplements, solvents, plasticizers, lubricants, and even biofuels such as sustainable aviation fuel.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Standardized protocols and procedures can precisely and accurately quantify non-structural carbohydrates

Non-structural carbohydrates (NSCs), the stored products of photosynthesis, building blocks for growth, and fuel for respiration, are central to plant metabolism, but their measurement is challenging. Differences in methods and procedures among laboratories can cause results to vary widely, limiting our ability to integrate and generalize patterns in plant C balance among studies. A recent assessment found that NSC concentrations measured for a common set of samples can vary by an order of magnitude, but sources for this variability were unclear. We measured a common set of nine plant material types, and two synthetic samples with known NSC concentrations, using a common protocol for sugar extraction and starch digestion, and three different sugar quantification methods (ion chromatography, enzyme, acid) in six laboratories. We also tested how sample handling, extraction solvent, and centralizing parts of the procedure in one laboratory affected results. NSC concentrations measured for synthetic samples were within about 11.5% of known values for all three methods. However, differences among quantification methods were the largest source of variation in NSC measurements for natural plant samples because the three methods quantify different NSCs. The enzyme method quantified only glucose, fructose, and sucrose, with ion chromatography we additionally quantified galactose, while the acid method quantified a large range of mono- and oligosaccharides. For some natural samples, acid method quantification doubled sugar relative to the other methods, demonstrating that trees allocate C to a range of sugar molecules. Sample handling had little effect on measurements, while ethanol sugar extraction improved accuracy over water extraction. Our results demonstrate that reasonable accuracy of NSC measurements can be achieved when different methods are used, as long as protocols are robust and standardized. Thus, we provide detailed protocols for the extraction, digestion and quantification of NSCs in plant samples, which should improve the comparability of NSC measurements among laboratories.

Landhäusser, Simon M.↗
DOE OSTI2023

Circulating Current Reduction of Back-to-Back MMC with Advanced Grid-Support Functionalities for Medium-Voltage Applications

A Lyapunov energy function based circulating current reduction scheme for a back to back modular multilevel converter based system for a microgrid application has been proposed in this digest. In order to ensure no circulating or zero sequence currents within the modules, the dynamics from one leg of the converter to the other are evaluated. A Lyapunov energy function is then developed and utilizing the circulating current dynamics of the converter the overall control law is implemented. In this digest a decentralized hierarchical control architecture has been implemented for the main current control; where the outer loop or the central controller implements the higher level grid interconnection functions as per IEEE 1547-2018 standards and the inner loop based on synchronous reference frame implements the current control architecture. The inner loops' outputs are the commanded converter voltages either on either side which are augmented by the Lyapunov energy function based circulating current suppression architecture. To evaluate the efficacy of the overall system, the overall system is modeled around a 300kVA back to back SiC multilevel modular converter used as a direct-connected medium voltage (MV) grid intertie based on MATLAB/Simulink domain. Several important case studies are presented in this paper to prove the effectiveness of the proposed architecture. case study results are presented.

circulating current↗
DOE OSTI2018

Development and Validation of a SiC Based 50 kW Grid-Connected PV Inverter: Preprint

In this digest a 50kW string PV inverter formed using all SiC semiconductor devices is presented. The inverter design includes additively manufactured power block, symmetrical Y-core inductors for ac side filter, and advanced inverter functionality for grid support. This inverter utilizes the conventional three-phase Voltage Source Inverter topology and optimizes the design for SiC based devices. This paper presents the full functional validation of the designed inverter along with quantification of the efficiency and power density. The performance of the inverter for high dc-bus voltage without multi-level topology to exploit SiC advantages is also presented in this digest. The full paper will include details of inverter design, optimization and further experimental validation.

14 SOLAR ENERGY↗
DOE OSTI2015

Kinship, inbreeding and fine‐scale spatial structure influence gut microbiota in a hindgut‐fermenting tortoise

Abstract Herbivorous vertebrates rely on complex communities of mutualistic gut bacteria to facilitate the digestion of celluloses and hemicelluloses. Gut microbes are often convergent based on diet and gut morphology across a phylogenetically diverse group of mammals. However, little is known about microbial communities of herbivorous hindgut‐fermenting reptiles. Here, we investigate how factors at the individual level might constrain the composition of gut microbes in an obligate herbivorous reptile. Using multiplexed 16S rRNA gene sequencing, we characterized the faecal microbial community of a population of gopher tortoises ( Gopherus polyphemus ) and examined how age, genetic diversity, spatial structure and kinship influence differences among individuals. We recovered phylotypes associated with known cellulolytic function, including candidate phylum Termite Group 3, suggesting their importance for gopher tortoise digestion. Although host genetic structure did not explain variation in microbial composition and community structure, we found that fine‐scale spatial structure, inbreeding, degree of relatedness and possibly ontogeny shaped patterns of diversity in faecal microbiomes of gopher tortoises. Our findings corroborate widespread convergence of faecal‐associated microbes based on gut morphology and diet and demonstrate the role of spatial and demographic structure in driving differentiation of gut microbiota in natural populations.

Yuan, Michael L.↗
DOE OSTI2024

Altering the substitution and cross‐linking of glucuronoarabinoxylans affects cell wall architecture in Brachypodium distachyon

Summary The Poaceae family of plants provides cereal crops that are critical for human and animal nutrition, and also, they are an important source of biomass. Interacting plant cell wall components give rise to recalcitrance to digestion; thus, understanding the wall molecular architecture is important to improve biomass properties. Xylan is the main hemicellulose in grass cell walls. Recently, we reported structural variation in grass xylans, suggesting functional specialisation and distinct interactions with cellulose and lignin. Here, we investigated the functions of these xylans by perturbing the biosynthesis of specific xylan types. We generated CRISPR/Cas9 knockout mutants in Brachypodium distachyon XAX1 and GUX2 genes involved in xylan substitution. Using carbohydrate gel electrophoresis, we identified biochemical changes in different xylan types. Saccharification, cryo‐SEM, subcritical water extraction and ssNMR were used to study wall architecture. Bd XAX1A and Bd GUX2 enzymes modify different types of grass xylan. Brachypodium mutant walls are likely more porous, suggesting the xylan substitutions directed by both Bd XAX1A and GUX2 enzymes influence xylan‐xylan and/or xylan–lignin interactions. Since xylan substitutions influence wall architecture and digestibility, our findings open new avenues to improve cereals for food and to use grass biomass for feed and the production of bioenergy and biomaterials.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

In Vivo and In Vitro Effects of a ClpP-Activating Antibiotic against Vancomycin-Resistant Enterococci

ABSTRACT Antibiotics with novel bactericidal mechanisms of action are urgently needed. The antibiotic acyldepsipeptide 4 (ADEP4) activates the ClpP protease and causes cells to self-digest. The effects of ADEP4 and ClpP activation have not been characterized sufficiently for the enterococci, which are important pathogens known for high levels of acquired and intrinsic antibiotic resistance. In the present study, ADEP4 was found to be potently active against both Enterococcus faecalis and Enterococcus faecium , with MIC 90 s of 0.016 μg/ml and 0.031 μg/ml, respectively. ClpP purified from E. faecium was found to bind ADEP4 in a surface plasmon resonance analysis, and ClpP activation by ADEP4 was demonstrated biochemically with a β-casein digestion assay. In addition, E. faecium ClpP was crystallized in the presence of ADEP4, revealing ADEP4 binding to ClpP in the activated state. These results confirm that the anti-enterococcal activity of ADEP4 occurs through ClpP activation. In killing curve assays, ADEP4 was found to be bactericidal against stationary-phase vancomycin-resistant E. faecalis (VRE) strain V583, and resistance development was prevented when ADEP4 was combined with multiple classes of approved antibiotics. ADEP4 in combination with partnering antibiotics also eradicated mature VRE biofilms within 72 h of treatment. Biofilm killing with ADEP4 antibiotic combinations was superior to that with the clinically used combinations ampicillin-gentamicin and ampicillin-daptomycin. In a murine peritoneal septicemia model, ADEP4 alone was as effective as ampicillin. ADEP4 coadministered with ampicillin was significantly more effective than either drug alone. These data suggest that ClpP-activating antibiotics may be useful for treating enterococcal infections.

Brown Gandt, Autumn↗
DOE OSTI2017

Accurate Quantification of Laminarin in Marine Organic Matter with Enzymes from Marine Microbes

Marine algae produce a variety of glycans, which fulfill diverse biological functions and fuel the carbon and energy demands of heterotrophic microbes. A common approach to analysis of marine organic matter uses acid to hydrolyze the glycans into measurable monosaccharides. The monosaccharides may be derived from different glycans that are built with the same monosaccharides, however, and this approach does not distinguish between glycans in natural samples. Here we use enzymes to digest selectively and thereby quantify laminarin in particulate organic matter. Environmental metaproteome data revealed carbohydrate-active enzymes from marine flavobacteria as tools for selective hydrolysis of the algal β-glucan laminarin. The enzymes digested laminarin into glucose and oligosaccharides, which we measured with standard methods to establish the amounts of laminarin in the samples. We cloned, expressed, purified, and characterized three new glycoside hydrolases (GHs) of Formosa bacteria: two are endo-β-1,3-glucanases, of the GH16 and GH17 families, and the other is a GH30 exo-β-1,6-glucanase. Formosa sp. nov strain Hel1_33_131 GH30 (FbGH30) removed the β-1,6-glucose side chains, and Formosa agariphila GH17A (FaGH17A) and FaGH16A hydrolyzed the β-1,3-glucose backbone of laminarin. Specificity profiling with a library of glucan oligosaccharides and polysaccharides revealed that FaGH17A and FbGH30 were highly specific enzymes, while FaGH16A also hydrolyzed mixed-linked glucans with β-1,4-glucose. Therefore, we chose the more specific FaGH17A and FbGH30 to quantify laminarin in two cultured diatoms, namely, Thalassiosira weissflogii and Thalassiosira pseudonana , and in seawater samples from the North Sea and the Arctic Ocean. Combined, these results demonstrate the potential of enzymes for faster, stereospecific, and sequence-specific analysis of select glycans in marine organic matter.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Activity-Based Protein Profiling of Ammonia Monooxygenase in Nitrosomonas europaea

Nitrosomonas europaea is an aerobic nitrifying bacterium that oxidizes ammonia (NH 3 ) to nitrite (NO 2 ₋ ) through the sequential activities of ammonia monooxygenase (AMO) and hydroxylamine dehydrogenase (HAO). Many alkynes are mechanism-based inactivators of AMO, and here we describe an activity-based protein profiling method for this enzyme using 1,7-octadiyne (17OD) as a probe. Inactivation of NH 4 + -dependent O 2 uptake by N. europaea by 17OD was time- and concentration-dependent. The effects of 17OD were specific for ammonia-oxidizing activity, and de novo protein synthesis was required to reestablish this activity after cells were exposed to 17OD. Cells were reacted with Alexa Fluor 647 azide using a copper-catalyzed azide-alkyne cycloaddition (CuAAC) (click) reaction, solubilized, and analyzed by SDS-PAGE and infrared (IR) scanning. A fluorescent 28-kDa polypeptide was observed for cells previously exposed to 17OD but not for cells treated with either allylthiourea or acetylene prior to exposure to 17OD or for cells not previously exposed to 17OD. The fluorescent polypeptide was membrane associated and aggregated when heated with β-mercaptoethanol and SDS. The fluorescent polypeptide was also detected in cells pretreated with other diynes, but not in cells pretreated with structural homologs containing a single ethynyl functional group. The membrane fraction from 17OD-treated cells was conjugated with biotin-azide and solubilized in SDS. Streptavidin affinity-purified polypeptides were on-bead trypsin-digested, and amino acid sequences of the peptide fragments were determined by liquid chromatography-mass spectrometry (LC-MS) analysis. Peptide fragments from AmoA were the predominant peptides detected in 17OD-treated samples. In-gel digestion and matrix-assisted laser desorption ionization–tandem time of flight (MALDI-TOF/TOF) analyses also confirmed that the fluorescent 28-kDa polypeptide was AmoA.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2024

Enrichable consortia of microbial symbionts degrade macroalgal polysaccharides in Kyphosus fish

ABSTRACT Coastal herbivorous fishes consume macroalgae, which is then degraded by microbes along their digestive tract. However, there is scarce genomic information about the microbiota that perform this degradation. This study explores the potential of Kyphosus gastrointestinal microbial symbionts to collaboratively degrade and ferment polysaccharides from red, green, and brown macroalgae through in silico study of carbohydrate-active enzyme and sulfatase sequences. Recovery of metagenome-assembled genomes (MAGs) from previously described Kyphosus gut metagenomes and newly sequenced bioreactor enrichments reveals differences in enzymatic capabilities between the major microbial taxa in Kyphosus guts. The most versatile of the recovered MAGs were from the Bacteroidota phylum, whose MAGs house enzyme collections able to decompose a variety of algal polysaccharides. Unique enzymes and predicted degradative capacities of genomes from the Bacillota (genus Vallitalea ) and Verrucomicrobiota (order Kiritimatiellales ) highlight the importance of metabolic contributions from multiple phyla to broaden polysaccharide degradation capabilities. Few genomes contain the required enzymes to fully degrade any complex sulfated algal polysaccharide alone. The distribution of suitable enzymes between MAGs originating from different taxa, along with the widespread detection of signal peptides in candidate enzymes, is consistent with cooperative extracellular degradation of these carbohydrates. This study leverages genomic evidence to reveal an untapped diversity at the enzyme and strain level among Kyphosus symbionts and their contributions to macroalgae decomposition. Bioreactor enrichments provide a genomic foundation for degradative and fermentative processes central to translating the knowledge gained from this system to the aquaculture and bioenergy sectors. IMPORTANCE Seaweed has long been considered a promising source of sustainable biomass for bioenergy and aquaculture feed, but scalable industrial methods for decomposing terrestrial compounds can struggle to break down seaweed polysaccharides efficiently due to their unique sulfated structures. Fish of the genus Kyphosus feed on seaweed by leveraging gastrointestinal bacteria to degrade algal polysaccharides into simple sugars. This study reconstructs metagenome-assembled genomes for these gastrointestinal bacteria to enhance our understanding of herbivorous fish digestion and fermentation of algal sugars. Investigations at the gene level identify Kyphosus guts as an untapped source of seaweed-degrading enzymes ripe for further characterization. These discoveries set the stage for future work incorporating marine enzymes and microbial communities in the industrial degradation of algal polysaccharides.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Molecular Dissection of Xyloglucan Recognition in a Prominent Human Gut Symbiont

ABSTRACT Polysaccharide utilization loci (PUL) within the genomes of resident human gut Bacteroidetes are central to the metabolism of the otherwise indigestible complex carbohydrates known as “dietary fiber.” However, functional characterization of PUL lags significantly behind sequencing efforts, which limits physiological understanding of the human-bacterial symbiosis. In particular, the molecular basis of complex polysaccharide recognition, an essential prerequisite to hydrolysis by cell surface glycosidases and subsequent metabolism, is generally poorly understood. Here, we present the biochemical, structural, and reverse genetic characterization of two unique cell surface glycan-binding proteins (SGBPs) encoded by a xyloglucan utilization locus (XyGUL) from Bacteroides ovatus , which are integral to growth on this key dietary vegetable polysaccharide. Biochemical analysis reveals that these outer membrane-anchored proteins are in fact exquisitely specific for the highly branched xyloglucan (XyG) polysaccharide. The crystal structure of SGBP-A, a SusD homolog, with a bound XyG tetradecasaccharide reveals an extended carbohydrate-binding platform that primarily relies on recognition of the β-glucan backbone. The unique, tetra-modular structure of SGBP-B is comprised of tandem Ig-like folds, with XyG binding mediated at the distal C-terminal domain. Despite displaying similar affinities for XyG, reverse-genetic analysis reveals that SGBP-B is only required for the efficient capture of smaller oligosaccharides, whereas the presence of SGBP-A is more critical than its carbohydrate-binding ability for growth on XyG. Together, these data demonstrate that SGBP-A and SGBP-B play complementary, specialized roles in carbohydrate capture by B. ovatus and elaborate a model of how vegetable xyloglucans are accessed by the Bacteroidetes . IMPORTANCE The Bacteroidetes are dominant bacteria in the human gut that are responsible for the digestion of the complex polysaccharides that constitute “dietary fiber.” Although this symbiotic relationship has been appreciated for decades, little is currently known about how Bacteroidetes seek out and bind plant cell wall polysaccharides as a necessary first step in their metabolism. Here, we provide the first biochemical, crystallographic, and genetic insight into how two surface glycan-binding proteins from the complex Bacteroides ovatus xyloglucan utilization locus (XyGUL) enable recognition and uptake of this ubiquitous vegetable polysaccharide. Our combined analysis illuminates new fundamental aspects of complex polysaccharide recognition, cleavage, and import at the Bacteroidetes cell surface that may facilitate the development of prebiotics to target this phylum of gut bacteria.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Stable Highly Enriched Isotopes in Routine Analysis of Rocks, Soils, Grounds, and Sediments by ICP-MS

Two procedures of acid digestion in an open system and in autoclaves are developed for routine ICP-AES and ICP-MS analysis of rocks, soils, grounds, and sediments. Proposed is a technique based on the use of stable highly enriched isotopes produced in Russia which enables the control (although with certain limitations) over the digestion procedure for each analyzed sample.

58 GEOSCIENCES↗
DOE OSTI2020

Effect of Natural Fermentation of Sorghum on Resistant Starch Molecular Structure and Fermentation Property

Relevant research results have suggested that fermentation can increase the content of sorghum amylose chains and their retrogradation value. Therefore, this study explored the effect of fermentation pretreatment on the yield, digestibility, molecular structure, and in vitro fermentation property of sorghum-resistant starch by conducting fermentation pretreatment of sorghum and extracting the resistant starch from fermented sorghum with pressure-heat compound enzyme method. The results were as follows. After fermentation pretreatment, the yield of sorghum-resistant starch increased, the digestibility of sorghum-resistant starch reduced, the laminated structure size on the surface of the particles became more uniform, and the stacking mode became more neat and denser. The sorghum-resistant starch prepared before and after fermentation did not produce new chemical groups, and its functional group peak remained unchanged. After fermentation, the weight-average molecular weight of sorghum-resistant starch was elevated, and the percentage content of high- and low-molecular substances increased and decreased, respectively, compared with that of the unfermented sorghum-resistant starch. The percentage content of short-chain branches in the branched chain increased, whereas that of the long-chain branches decreased; the crystallinity of sorghum-resistant starch after fermentation decreased, and the intensity of X-diffraction peak changed slightly before and after fermentation. According to the results of the in vitro fermentation experiments, the fermentation broth of sorghum-resistant starch had the highest content of butyric acid and short-chain fatty acid. Research results reveal that, after fermentation pretreatment, sorghum-resistant starch presented increased yield, more complex molecular structure, heavier molecular weight and more uniform surface morphology, more efficient butyric acid generation, and greater fermentation rate than unfermented sorghum-resistant starch.

Ge, YunFei↗