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Evans, Barbara R.

Publications and source records attributed to Evans, Barbara R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Iron Impurity Impairs the CO 2 Capture Performance of MgO: Insights from Microscopy and Machine Learning Molecular Dynamics

Magnesium oxide (MgO) is a promising sorbent for direct air capture (DAC) of carbon dioxide. Iron (Fe) is a common impurity in naturally occurring MgO and minerals used to produce MgO, yet a molecular-scale understanding of Fe-doping effects on carbonation is lacking. Here, in this study, we observed reduced carbonation performance in Fe-doped MgO experimentally. The energetics of adsorbing a (bi)carbonate ion on pristine and Fe-doped MgO(001) surfaces were further investigated using ab initio and machine learning potential molecular dynamics coupled with metadynamics simulations. Both pristine and Fe-doped surfaces exhibited a basic (OH – ) hydration layer, where the (bi)carbonate ion adsorption is thermodynamically favorable. However, the dissolution of surface Fe had smaller energy barriers and was more favorable than Mg. Leached Fe likely neutralized the near-surface basicity, yielding reduced reactivity on Fe-doped MgO. Our observations offer critical insights for material selection and emphasize the importance of evaluating the geologic origin of earth materials used for DAC.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A New Triketone Ligand for Extraction of Lithium from Brines**

Recovery of lithium from brines by liquid-liquid solvent extraction (LLE) with diketones and synergistic co-ligands has been investigated for decades, but industrial application has been limited. In pursuit of a ligand with improved properties, a series of ketonamides with beta-carbonyl groups were designed, synthesized, and tested in extraction of lithium from sulfate and carbonate simulants of clay mineral tailing leachates. The best performing ligand, a novel tricarbonyl amide, was characterized for lithium extraction with and without four synergistic co-ligands. Further, the tricarbonyl amide combined with the synergistic co-ligand Cyanex-923 was absorbed on a resin support. The ligand-modified resin was tested for performance in extraction of dilute brine simulants and up to 60 % recovery of lithium was achieved.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Deconvoluting Structures of Component Plant Biopolymers Using Deuterium Labeled Brassica oleracea Stems

Several Brassica species are cultivated globally for the production of seed oils as food, lubricants, and increasingly biofuels. The stem and leaf residues of these herbaceous dicotyledonous crops constitute another feedstock for biofuels and other products. Plant cell walls are complex, multipolymeric structures that consist primarily of polysaccharides and lignin. Cellulose chains coalesce to form crystalline microfibrils while the amorphous biopolymers, hemicellulose, and lignin form a network structure and fill the interstitial space. Neutron scattering has been used for the structural study of the assembly and deconstruction of the plant cell walls. However, similar neutron sensitivity of the different amorphous biopolymers has made structural association to individual component biopolymers nontrivial and ambiguous. To improve the association of structural features to specific biopolymer components, partial deuteration of the plant cell wall can be employed to increase the difference in the neutron scattering length density between amorphous carbohydrate and lignin plant polymers. Vegetative stems from partially deuterated Brassica oleracea acephala (kale) plants were obtained commercially, and the plant cell wall structures were studied by contrast-variation small-angle neutron scattering (CV-SANS) and Fourier-transform infrared spectroscopy (FTIR). FTIR results indicated that deuterium substitution for hydrogen in the carbohydrates was higher than that in lignin. By combining CV-SANS and FTIR results, the neutron scattering length density (nSLD) of the polysaccharides and lignin was determined to match nSLD of 65%:35% and 48%:52% D 2 O/H 2 O solvent mixtures, respectively. These nSLD values were higher than the nSLD values of polysaccharides and lignin for H 2 O grown biopolymers. The nSLD increase correlates to replacing about 42.5% of hydrogens present as both C–H and O–H groups in cellulose with deuterium atoms, while only 21% for lignin. In conclusion, this study lays the foundation to use partially deuterated plants to deconvolute structural features of the different component biopolymers, especially cellulose, hemicellulose, and lignin, of the plant cell wall without introducing unintended structural modifications due to the pretreatment extraction processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Chemical and Morphological Structure of Transgenic Switchgrass Organosolv Lignin Extracted by Ethanol, Tetrahydrofuran, and $\mathcal{γ}$-Valerolactone Pretreatments

We report the recalcitrance of lignocellulosic biomass is a challenge in biological-based biorefinery systems due to the complex physicochemical structure of plant cell walls. Pretreatment and genetic modification are two approaches in biomass conversion that have succeeded in modifying the structure of lignocellulose to enable better enzymatic deconstruction. However, the structural differences among pretreatment-solubilized lignin isolated from switchgrass genotypes have not been extensively investigated. Here, three organosolv pretreatment systems-ethanol (EtOH), tetrahydrofuran (THF), and γ-valerolactone (GVL)-were used on wild-type (WT) and two transgenic switchgrasses. All organosolv pretreatments caused a significant reduction in the molecular mass of lignins; particularly, up to ~90% decrease was observed in EtOH-pretreated lignin compared to untreated lignin. The WT EtOH lignin also presented the smallest particle size among all WT lignins. THF pretreated transgenic lignins showed a higher molecular mass, β-O-4 linkages, and aliphatic hydroxyl content compared to EtOH and GVL pretreated lignin. The number of hydrogen bonds between lignin and the organic solvents calculated from the molecular dynamics simulations followed the same trend as the experimentally determined reduction in lignin molecular mass. The results revealed the structural changes of solubilized lignin isolated from wild-type and transgenic switchgrass after different organosolv pretreatments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Deuterium incorporation into cellulose: a mini-review of biological and chemical methods

Isotopic enrichment offers structural insights that are not easily accessible with natural abundance isotopic composition. Deuterated cellulose has attracted considerable attention in the field of neutron scattering studies, providing information about the dynamics, structure of cellulose and its interactions with other plant cell wall components. The deuteration of cellulose also allows the analysis of cellulose hydrogen bonds by FTIR or NMR techniques. The chemical structure of cellulose contains both exchangeable hydroxyl and non-exchangeable alkyl hydrogens. Deuterium incorporation can be divided into two classifications: biological route which incorporates both alkyl and hydroxyl bound deuterium, and chemical route which typically replaces hydroxyl-bound exchangeable hydrogen. Additionally, the biological route involves cultivating plants or microorganisms in a deuterium-enriched medium. The chemical route typically involves an exchange reaction between hydroxyl-bound hydrogen and D 2 O, often facilitating with an alkaline reagent. This review provides an overview of recent advances in deuteration methods and characterization as well as the application of deuterated cellulose.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Structural Reorganization of Noncellulosic Polymers Observed In Situ during Dilute Acid Pretreatment by Small-Angle Neutron Scattering

Production of second-generation bioethanol from lignocellulosic biomass requires pretreatment to open the plant cell wall structure and improve enzyme access. Many different thermochemical pretreatments have been extensively developed and employed, but the exact nature of plant cell wall recalcitrance and the most efficient and economical approach to alter plant cell wall structure via pretreatment still remain elusive. In order to understand the role of noncellulosic switchgrass polymers on the overall efficiency of pretreatment, the structural evolution of the noncellulosic polymers of the plant cell wall were investigated during dilute acid pretreatment (DAP) by employing in-situ small-angle neutron scattering (in-situ SANS). In this study, we observed real-time structural changes not possible to observe by any other technique. To deconvolute the structural evolution of lignin and hemicellulose polymers during DAP, native switchgrass (NATV), and isolated holocellulose (HOLO) and cellulose (CELL) fractions from NATV were studied. Our results show that aggregate particles first appear around 80 °C for NATV and HOLO samples. Further, due to the low temperature and pretreatment severity condition, these particles are likely derived from hemicellulose. The formations of much larger aggregate particles, only observed in the NATV sample, were attributed to lignin. For the HOLO sample, as the temperature and pretreatment severity condition increased, hemicellulose-derived aggregate particle sizes increased, suggesting this process was the nucleation and early stage formation of pseudolignin particles. Consistent with our interpretation of structural evolutions in NATV and HOLO samples, no formation of aggregate particles was observed in CELL samples for the entire duration of the pretreatment. These results suggest that not only lignin but also hemicellulose can form aggregate particles within plant cell walls during pretreatment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Effects of soil particles and convective transport on dispersion and aggregation of nanoplastics via small-angle neutron scattering (SANS) and ultra SANS (USANS)

Terrestrial nanoplastics (NPs) pose a serious threat to agricultural food production systems due to the potential harm of soil-born micro- and macroorganisms that promote soil fertility and ability of NPs to adsorb onto and penetrate into vegetables and other crops. Very little is known about the dispersion, fate and transport of NPs in soils. This is because of the challenges of analyzing terrestrial NPs by conventional microscopic techniques due to the low concentrations of NPs and absence of optical transparency in these systems. Herein, we investigate the potential utility of small-angle neutron scattering (SANS) and Ultra SANS (USANS) to probe the agglomeration behavior of NPs prepared from polybutyrate adipate terephthalate, a prominent biodegradable plastic used in agricultural mulching, in the presence of vermiculite, an artificial soil. SANS with the contrast matching technique was used to study the aggregation of NPs co-dispersed with vermiculite in aqueous media. We determined the contrast match point for vermiculite was 66% D 2 O / 33% H 2 O. At this condition, the signal for vermiculite was ~50–100%-fold lower that obtained using neat H 2 O or D 2 O as solvent. According to SANS and USANS, smaller-sized NPs (50 nm) remained dispersed in water and did not undergo size reduction or self-agglomeration, nor formed agglomerates with vermiculite. Larger-sized NPs (300–1000 nm) formed self-agglomerates and agglomerates with vermiculite, demonstrating their significant adhesion with soil. However, employment of convective transport (simulated by ex situ stirring of the slurries prior to SANS and USANS analyses) reduced the self-agglomeration, demonstrating weak NP-NP interactions. Convective transport also led to size reduction of the larger-sized NPs. Therefore, this study demonstrates the potential utility of SANS and USANS with contrast matching technique for investigating behavior of terrestrial NPs in complex soil systems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

A disposable bulk-acoustic-wave microalga trapping device for real-time water monitoring

Recently, there has been an increase in the use of algal physiology as a convenient and useful indicator for monitoring of water quality in aquatic ecosystems. However, current methods for monitoring algal physiology are high-cost, power intensive, and have limited sensitivity for practical samples in which algal concentration is low. In order to alleviate these problems, we developed a simple-to-fabricate acoustophoretic particle trapping device that can effectively enrich various types of microalgae such as chlorella and diatoms for real-time monitoring of water quality. This microalgae trap is fabricated by embedding a piezoelectric resonator in a single channel. In comparison to previously reported acoustophoretic particle traps, this device has a simple structure and does not require sheath flows, which makes the device low cost and simple to fabricate and operate. Using Chlorella kessleri and the marine diatom Thalassiosira pseudonana as model algae, we report the microalgae trap has demonstrated notable particle trapping efficiencies between 82 % to 74 % for Chlorella with a through-flow of 0.5 μl/min to 2.7 μl/min and 85 % to 79 % for diatoms with a 0.5 μl/min to 4 μl/min through-flow. The trap has also shown to simultaneously trap Chlorella and diatoms at different heights of the microchannel. This device has high promise for trapping, separating and manipulating microalgae.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Production of deuterated biomass by cultivation of Lemna minor (duckweed) in D 2 O

The small aquatic plant duckweed, particularly the genus Lemna , widely used for toxicity testing, has been proposed as a potential source of biomass for conversion into biofuels as well as a platform for production of pharmaceuticals and specialty chemicals. Ability to produce deuterium-substituted duckweed can potentially extend the range of useful products as well as assist process improvement. Cultivation of these plants under deuterating conditions was previously been reported to require addition of kinetin to induce growth and was hampered by anomalies in cellular morphology and protein metabolism. Here, we report the production of biomass with 50–60% deuterium incorporation by long-term photoheterotrophic growth of common duckweed Lemna minor in 50% D 2 O with 0.5% glucose. L. minor grown in 50% D 2 O without addition of kinetin exhibited a lag phase twice that of H 2 O-grown controls, before start of log phase growth at 40% of control rates. Compared to continuous white fluorescent light, growth rates increased fivefold for H 2 O and twofold for 50% D 2 O when plants were illuminated at higher intensity with a metal halide lamp and a diurnal cycle of 12-h light/12-h dark. Deuterium incorporation was determined by a combination of 1 H and 2 H nuclear magnetic resonance (NMR) to be 40–60%. The cellulose from the deuterated plants had an average-number degree of polymerization (DP n ) and polydispersity index (PDI) close to that of H 2 O-grown controls, while Klason lignin content was reduced. Furthermore, the only major gross morphological change noted was root inhibition.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Hemicellulose–Cellulose Composites Reveal Differences in Cellulose Organization after Dilute Acid Pretreatment

Model hemicellulose–cellulose composites that mimic plant cell wall polymer interactions were prepared by synthesizing deuterated bacterial cellulose in the presence of glucomannan or xyloglucan. Dilute acid pretreatment (DAP) of these materials was studied using small-angle neutron scattering, X-ray diffraction, and sum frequency generation spectroscopy. The macrofibril dimensions of the pretreated cellulose alone were smaller but with similar entanglement of macrofibrillar network as native cellulose. In addition, the crystallite size dimension along the (010) plane increased. Glucomannan–cellulose underwent similar changes to cellulose, except that the macrofibrillar network was more entangled after DAP. Conversely, in xyloglucan–cellulose the macrofibril dimensions and macrofibrillar network were relatively unchanged after pretreatment, but the cellulose I β content was increased. Our results point to a tight interaction of xyloglucan with microfibrils while glucomannan only interacts with macrofibril surfaces. Furthermore, this study provides insight into roles of different hemicellulose–cellulose interactions and may help in improving pretreatment processes or engineering plants with decreased recalcitrance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Ultrastructure and Enzymatic Hydrolysis of Deuterated Switchgrass

Neutron scattering of deuterated plants can provide fundamental insight into the structure of lignocellulosics in plant cell walls and its deconstruction by pretreatment and enzymes. Such plants need to be characterized for any alterations to lignocellulosic structure caused by growth in deuterated media. Here we show that glucose yields from enzymatic hydrolysis at lower enzyme loading were 35% and 30% for untreated deuterated and protiated switchgrass, respectively. Lignin content was 4% higher in deuterated switchgrass but there were no significant lignin structural differences. Transmission electron microscopy showed differences in lignin distribution and packing of fibers in the cell walls that apparently increased surface area of cellulose in deuterated switchgrass, increasing cellulose accessibility and lowering its recalcitrance. These differences in lignification were likely caused by abiotic stress due to growth in deuterated media.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Hemicellulose characterization of deuterated switchgrass

This paper describes the structural characterization of hemicellulose isolated from hydroponically grown switchgrass in H 2 O medium (protiated) or 50% D 2 O medium (deuterated) through compositional analysis, GPC, FTIR, 13 C and 1 H/ 13 C HSQC NMR. 4-O-methyl glucuronoarabinoxylan (GAX), the major hemicellulose in switchgrass isolated from deuterated switchgrass, had structural properties similar to hemicellulose isolated from protiated switchgrass. Both had comparable arabinose to xylose ratio (0.25) and molecular weight (47–50 kDa). Finally, structural similarities show that deuterated switchgrass hemicellulose can be used as a model carbohydrate polymer in neutron scattering, or pharmaceutical studies due to their immunomodulatory activity and gastroprotective effects.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Effect of in Vivo Deuteration on Structure of Switchgrass Lignin

Biomass deuteration is an effective engineering method that can be used to provide key insights into understanding of biomass recalcitrance and the complex biomass conversion process. In this study, production of deuterated switchgrass was accomplished by growing the plants in 50% D 2 O under hydroponic conditions in a perfusion chamber. Cellulolytic enzyme lignin was isolated from deuterated switchgrass, characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) and compared with its protiated control sample to determine the effect of in vivo deuteration on the chemical structure of lignin. FTIR results showed that D 2 O can be taken up by the roots and transported to the leaves, and deuterium was subsequently incorporated into hydroxyl and alkyl groups in the plant and its lignin through photosynthesis. According to GPC results, deuterated lignin had slightly higher molecular weight, presumably due to isotope effects. 31 P and heteronuclear single quantum coherence (HSQC) NMR results revealed that lignin in the deuterated biomass preserved its native physicochemical characteristics. Finally, the conserved characteristics of the deuterated lignin show its great potential applications for structural and dynamic studies of lignocellulose by techniques such as neutron scattering.

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

Allelopathic effects of exogenous phenylalanine: a comparison of four monocot species

Isotopic labeling of biomolecules through biosynthesis from deuterated precursors has successfully been employed for both structural studies and metabolic analysis. Phenylalanine is the precursor of many products synthesized by plants, including the monolignols used for synthesis of lignin. Possible allelochemical effects of phenylalanine have not been reported, although its deamination product cinnamic acid is known to have deleterious effects on root elongation and growth of several plant species. In this work, the effects of phenylalanine and its deuterated analog phenylalanine-d8 added to growth media were studied for annual ryegrass (Lolium multiflorum), winter grain rye (Secale cereale), and switchgrass (Panicum virgatum) cultivated under hydroponic conditions. Growth of annual ryegrass was inhibited by phenylalanine while switchgrass and rye were not significantly affected. Growth was less affected by deuterated phenylalanine-d8 than by its protiated counterpart, which may be a typical deuterium kinetic isotope effect resulting in slower enzymatic reaction rates. Deuterium incorporation levels of 2-3% were achieved in biomass of switchgrass and annual ryegrass. Both protiated and deuterated phenylalanine were moderately toxic (IC25 values 0.6 and 0.8 mM, respectively) to duckweed (Lemna minor) grown using a 12 h diurnal cycle under photoautotrophic conditions. A significant increase in toxicity, greater for the deuterated form, was noted when duckweed was grown under higher intensity, full spectrum illumination with a metal halide lamp compared to fluorescent plant growth lamps emitting in the blue and red spectral regions. Lastly, supplementation with glucose increased toxicity of phenylalanine consistent with synergy between hexose and amino acid uptake that has been reported for duckweed.

09 BIOMASS FUELS↗
DOE OSTI2016

A resettable in-line particle concentrator using AC electrokinetics for distributed monitoring of microalgae in source waters

Green algae have been studied as an important and effective biomarker to indicate water quality due to their sensitivity to toxic agents in freshwater sources. But, conventional methods to monitor algal physiology use a chlorophyll fluorometer whose use is hampered by high-cost, large footprint, and limited sensitivity for practical samples containing low algal concentration. In order to overcome these constraints, we developed a multi-level electrode platform for resettable trapping of algae via AC electro-osmosis (ACEO) and negative dielectrophoresis. Preliminary experiments were performed in freshwater with conductivity of 0.02 S/m. Algal trapping was demonstrated at a low voltage of 2 V. The concentration effect was experimentally verified by measuring the fluorescence intensity of algae and using hemocytometer counting chambers at the inlet and outlet of the multilevel microchannel lab-on-a-chip. An optimal frequency was found for trapping, which agrees with the frequency dependence of ACEO flow velocity. Through-flow rate and electrode dimensions were optimized as well. Trapping efficiencies within the range of 26% - 65% have been obtained. A maximum trapping rate of 182 cells/s was obtained with a flow rate of 20 l/min. Our lab-on-a-chip shows high potential for improving the limit of detection in algal monitoring and enabling the development of a portable, integrated and automated system for monitoring the quality of source drinking waters.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Understanding Multiscale Structural Changes During Dilute Acid Pretreatment of Switchgrass and Poplar

Biofuels produced from lignocellulosic biomass hold great promise as a renewable alternative energy and fuel source. To realize a cost and energy efficient approach, a fundamental understanding of the deconstruction process is critically necessary to reduce biomass recalcitrance. Here, the structural and morphological changes over multiple scales (5–6000 Å) in herbaceous (switchgrass) and woody (hybrid poplar) biomass during dilute sulfuric acid pretreatment were explored using neutron scattering and X-ray diffraction. Switchgrass undergoes a larger increase (20–84 Å) in the average diameter of the crystalline core of the elementary cellulose fibril than hybrid poplar (19–50 Å). Switchgrass initially forms lignin aggregates with an average size of 90 Å that coalesce to 200 Å, which is double that observed for hybrid poplar, 55–130 Å. Switchgrass shows a smooth-to-rough transition in the cell wall surface morphology unlike the diffuse-to-smooth transition of hybrid poplar. Yet, switchgrass and hybrid poplar pretreated under the same experimental conditions result in pretreated switchgrass producing higher glucose yields (~76 wt %) than pretreated hybrid poplar (~60 wt %). This observation shows that other aspects like cellulose allomorph transitions, cellulose accessibility, cellular biopolymer spatial distribution, and enzyme–substrate interactions may be more critical in governing the enzymatic hydrolysis efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗