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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Topochemical Understanding of Lignin Distribution During Hydrothermal Flowthrough Pretreatment

Changes in surface properties during biomass pretreatments are important parameters to understand and engineer biological biomass conversion processes. In particular, different influences on the surface of biomass are expected between flowthrough and batch pretreatments. In this paper, for a better understanding of biomass surface changes by hydrothermal flowthrough pretreatment, the mechanism by which the surface of biomass is altered in terms of cellulose and lignin was investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and compared with the bulk chemical composition and the results from scanning electron microscope (SEM). ToF-SIMS analysis results provide semi-quantitative information of cellulose and lignin and support the other observation from SEM and bulk compositional analyses. In brief, more lignin was observed on the surface of biomass at the early stage hydrothermal pretreatment, while the lignin mainly located at the cell corners was reduced by extended pretreatment time. Finally, unlike batch pretreatment, pseudo-lignin formation was not observed on the poplar surface during the flowthrough process.

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

The best models of metabolism

Biochemical systems are among of the oldest application areas of mathematical modeling. Spanning a time period of over one hundred years, the repertoire of options for structuring a model and for formulating reactions has been constantly growing, and yet, it is still unclear whether or to what degree some models are better than others and how the modeler is to choose among them. In fact, the variety of options has become overwhelming and difficult to maneuver for novices and experts alike. This review outlines the metabolic model design process and discusses the numerous choices for modeling frameworks and mathematical representations. It tries to be inclusive, even though it cannot be complete, and introduces the various modeling options in a manner that is as unbiased as that is feasible. However, the review does end with personal recommendations for the choices of default models. WIREs Syst Biol Med 2017, 9:e1391. doi: 10.1002/wsbm.1391 This article is categorized under: Analytical and Computational Methods > Dynamical Methods Models of Systems Properties and Processes > Mechanistic Models Biological Mechanisms > Metabolism

Voit, Eberhard O.↗
DOE OSTI2018

Bioconversion of Methane for Value-Added Products

This chapter will briefly summarize the background of methane production from natural gas and biogas together with an introduction to the biomolecular basis of methanotrophy and the actual and potential commercial applications. This chapter also discusses the safety considerations for using methane in laboratory and safe development of methane-based bioprocesses. In the end, this chapter will focus on the process development for biological conversion of methane into desired products with attention to the enhancement of mass transfer efficiency and the development of bioreactor designs.

09 BIOMASS FUELS↗
DOE OSTI2018

Applications of KPFM-Based Approaches for Surface Potential and Electrochemical Measurements in Liquid

Kelvin probe force microscopy (KPFM) has been widely used to map nanoscale surface potentials of materials in ambient and ultra-high vacuum environments. However, to study and ultimately understand charge-related processes, e.g., in biological systems or to further improve energy storage devices such as electrochemical batteries, nanoscale surface potential measurements in liquid environments are required. Here, we describe the various implementations of KPFM-based approaches for measuring surface potentials in liquid environments. We provide practical guidelines for surface potential measurements and describe what other information can be obtained. Finally, we discuss potential applications and limitations of existing approaches and present possible solutions for the successful implementation of liquid KPFM.

Collins, Liam F.↗
DOE OSTI2020

Single-entity electrochemistry at confined sensing interfaces

Measurements at the single-entity level provide more precise diagnosis and understanding of basic biological and chemical processes. Recent advances in the chemical measurement provide a means for ultra-sensitive analysis. Confining the single analyte and electrons near the sensing interface can greatly enhance the sensitivity and selectivity. In this work, we summarize the recent progress in single-entity electrochemistry of single molecules, single particles, single cells and even brain analysis. The benefits of confining these entities to a compatible size sensing interface are exemplified. Finally, the opportunities and challenges of single entity electrochemistry are addressed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Seasonality of soil CO2 efflux in a temperate forest: Biophysical effects of snowpack and spring freeze–thaw cycles

Changes in characteristics of snowfall and spring freeze–thaw-cycle (FTC) events under the warming climate make it critical to understand biophysical controls on soil CO2 efflux (RS) in seasonally snow-covered ecosystems. We conducted a snow removal experiment and took year-round continuous automated measurements of RS, soil temperature (T5) and soil volumetric water content at the 5 cm depth (W5) with a half-hour interval in a Chinese temperate forest in 2010–2011. Our objectives were to: (1) develop statistical models to describe the seasonality of RS in this forest; (2) quantify the contribution of seasonal RS to the annual budget; (3) examine biophysical effects of snowpack on RS; and (4) test the hypothesis that an FTC-induced enhancement of RS is jointly driven by biological and physical processes.

Wang, Chuankuan↗
DOE OSTI2015

Snowpack-climate manipulation using infrared heaters in subalpine forests of the Southern Rocky Mountains, USA

Effects of infrared heaters on snow accumulation, snowmelt, and snow–atmosphere energy exchange were examined at Niwot Ridge, Colorado (CO) and compared to a naturally warmer, but otherwise similar subalpine site in the Valles Caldera National Preserve, New Mexico (NM). Observed snow accumulation was 30% lower on average and snow melted out 16 days earlier in the heated plots compared to the controls. Soil temperature during snowmelt was 3 °C greater on average and soil moisture was 4% lower on average in heated plots compared to controls. In NM, snow accumulation was 23% lower, snow melted 23 days earlier, soil temperature was 0.6 °C greater, and soil moisture was 13% lower on average relative to CO controls. In order to estimate differences in energy and mass balance fluxes at the snow–atmosphere interface in control versus warmer plots, the 1-D, physically based snowmelt model, SNOWPACK, was used. Model results indicated that heaters alter radiative, turbulent and mass fluxes by amounts comparable to the differences between CO and NM fluxes. The proportion of the energy flux associated with latent heat exchange during snowmelt was 9–27% of the total energy flux in heated models and 19–22% of NM models compared to 3–7% in control models. Thus, sublimation loss to the atmosphere was greater in both experimentally and naturally warmer cases relative to the control case. We conclude that IR heaters can provide alterations to the timing and magnitude of snow accumulation and snowmelt consistent with conditions observed at a warmer analog site and with climate and hydrology model projections. Finally, impacts of IR heating on energy partitioning and sublimation should be considered when designing manipulations of the snowpack, as reductions in snowmelt water may alter biological or ecological processes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Identification of Rbd2 as a candidate protease for sterol regulatory element binding protein (SREBP) cleavage in fission yeast

Lipid homeostasis in mammalian cells is regulated by sterol regulatory element-binding protein (SREBP) transcription factors that are activated through sequential cleavage by Golgi Site-1 and Site-2 proteases. Fission yeast SREBP, Sre1, engages a different mechanism involving the Golgi Dsc E3 ligase complex, but it is not clearly understood exactly how Sre1 is proteolytically cleaved and activated. In this study, we screened the Schizosaccharomyces pombe non-essential haploid deletion collection to identify missing components of the Sre1 cleavage machinery. Our screen identified an additional component of the SREBP pathway required for Sre1 proteolysis named rhomboid protein 2 (Rbd2). We show that an rbd2 deletion mutant fails to grow under hypoxic and hypoxia-mimetic conditions due to lack of Sre1 activity and that this growth phenotype is rescued by Sre1N, a cleaved active form of Sre1. We found that the growth inhibition phenotype under low oxygen conditions is specific to the strain with deletion of rbd2, not any other fission yeast rhomboid-encoding genes. Our study also identified conserved residues of Rbd2 that are required for Sre1 proteolytic cleavage. All together, our results suggest that Rbd2 is a functional SREBP protease with conserved residues required for Sre1 cleavage and provide an important piece of the puzzle to understand the mechanisms for Sre1 activation and the regulation of various biological and pathological processes involving SREBPs. - Highlights: • An rbd2-deleted yeast strain shows defects in growth in response to low oxygen levels. • rbd2-deficient cells fail to generate cleaved Sre1 (Sre1N) under hypoxic conditions. • Expression of Sre1N rescues the rbd2 deletion mutant growth phenotype. • Rbd2 contains conserved residues potentially critical for catalytic activity. • Mutation of the conserved Rbd2 catalytic residues leads to defects in Sre1 cleavage.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Cullin 3 regulates ADAMs-mediated ectodomain shedding of amphiregulin

Highlights: • ADAMs-mediated EGF family shedding is regulated by actin cytoskeleton. • Cul3 regulates AREG shedding by modulating actin cytoskeleton. • The neddylation is crucial step for Cul3 to regulate ectodomain shedding. • Cul3 E3 ubiquitin ligase complex is promising target to regulate ADAM activity. A disintegrin and metalloproteinase (ADAM) family are crucial enzymes for ectodomain shedding of multiple substrates and are involved in diverse biologic and pathologic processes. However, the molecular mechanism underlying substrate selectivity of ADAMs is poorly understood. In this study, we observed that disruption of actin polymerization by pharmacological inhibitors, latrunculin A (LatA) and cytochalasin D (CyD), induced ectodomain shedding of epidermal growth factor (EGF) family ligands. Induced shedding activity by LatA or CyD was suppressed by a metalloprotease inhibitor KB-R7785, indicating that ADAMs-mediated shedding is tightly controlled by actin cytoskeleton. We also investigated roles of cullin family, a component of cullin-RING based E3 ubiquitin ligases, in ectodomain shedding, since cullin family is implicated in the regulation of cytoskeletal dynamics. Knockdown of cullin 3 (Cul3) by a specific siRNA inhibited ectodomain shedding of amphiregulin (AREG), a member of EGF family, and responses were associated with activation of RhoA GTPase and induction of stress fiber formation. On the other hand, the RhoA inhibitor C3 transferase rescued AREG shedding reduced by Cul3 knockdown. These results describe a novel molecular mechanism of Cul3 to regulate AREG shedding by modulating cytoskeletal dynamics in a RhoA dependent manner.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Electrically controlling and optically observing the membrane potential of supported lipid bilayers

Supported lipid bilayers are a well-developed model system for the study of membranes and their associated proteins, such as membrane channels, enzymes, and receptors. These versatile model membranes can be made from various components, ranging from simple synthetic phospholipids to complex mixtures of constituents, mimicking the cell membrane with its relevant physiochemical and molecular phenomena. In addition, the high stability of supported lipid bilayers allows for their study via a wide array of experimental probes. In this work, we describe a platform for supported lipid bilayers that is accessible both electrically and optically, and demonstrate direct optical observation of the transmembrane potential of supported lipid bilayers. We show that the polarization of the supported membrane can be electrically controlled and optically probed using voltage-sensitive dyes. Membrane polarization dynamics is understood through electrochemical impedance spectroscopy and the analysis of an equivalent electrical circuit model. In addition, we describe the effect of the conducting electrode layer on the fluorescence of the optical probe through metal-induced energy transfer, and show that while this energy transfer has an adverse effect on the voltage sensitivity of the fluorescent probe, its strong distance dependency allows for axial localization of fluorescent emitters with ultrahigh accuracy. We conclude with a discussion on possible applications of this platform for the study of voltage-dependent membrane proteins and other processes in membrane biology and surface science.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Rewiring yeast metabolism for producing 2,3-butanediol and two downstream applications: Techno-economic analysis and life cycle assessment of methyl ethyl ketone (MEK) and agricultural biostimulant production

Rising concerns for sustainability and global climate change have driven the development of sustainable pro- duction pathways for biofuels and chemicals from lignocellulosic biomass via integrated biological and chemical processes. We constructed an engineered Saccharomyces cerevisiae capable of producing 2,3-butanediol (2,3-BDO) from glucose without accumulating ethanol and glycerol, which hinder downstream processing of 2,3-BDO, through extensive metabolic reprogramming. Specifically, we introduced heterologous 2,3-BDO biosynthetic enzymes and deleted the major isozymes of ethanol and glycerol biosynthetic enzymes. In addition, we introduced an NAD + regenerating Pyruvate-Malate (PM) cycle and enhanced the NAD + regenerating capability of the PM cycle to resolve the redox imbalance from the deletion of ethanol and glycerol production pathways. The resulting engineered yeast produced 109.9 g/L of 2,3-BDO with a productivity of 1.0 g/L/h and a yield of 0.36 g/ g glucose in a fed-batch fermentation. We also conducted techno-economic analysis (TEA) and life cycle assessment (LCA) of the production of methyl ethyl ketone (MEK) through catalytic dehydration of 2,3-BDO. A TEA based on the experimental results indicated that the minimum product selling price (MPSP) was estimated to be $1.90/kg. Regarding cradle-to-grave LCA, 100-year global warming potential (GWP100) and fossil energy consumption (FEC) were found to be 0.37 kg CO 2 eq/kg and 3.1 MJ/kg, respectively. These results demonstrated the feasibility of cost-competitive and sustainable bio-based MEK production via yeast fermentation. In addition, we explored the possibility of using the fermentation broth containing 2,3-BDO as a biostimulant inducing drought tolerance in plants. As a result, the yeast 2,3-BDO fermentation broth can induce drought tolerance in Arabidopsis thaliana without a complicated purification process.

2,3-butanediol (2,3-BDO)↗
DOE OSTI2021

Energy transduction by reversible electron bifurcation

Electron bifurcation is a biological energy conversion process that oxidizes a two-electron donor at medium potential, coupled to the reduction of a high- and a low-potential acceptor species. This process is often fully reversible (can occur close to ΔG ≈ 0), allowing the creation of strong reductants with minimal free energy cost, using compounds with higher reduction potentials. For many years, the internal workings of electron bifurcating enzymes were poorly understood, especially regarding how short-circuit reactions are prevented. Recently, a conserved energy landscape was proposed to naturally insulate against short-circuit reactions, enabling efficient and reversible electron bifurcation (the reversible EB scheme). Here, we review the physical principles that underpin the EB scheme, describe how the reversible EB scheme is distinct from previous views, and outline questions that remain open.

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

Contradictory effects of silver nanoparticles on activated sludge wastewater treatment

Increased amount of nano-silver will be released into domestic and industrial waste streams due to its extensive application. However, great controversy still exists on the effects of silver nanoparticle (Ag-NP) on biological wastewater treatment processes and a toxicology model has not been built yet. Four sequencing batch reactors with activated sludge has been run for over three months with different silver species at a concentration of 1 mg Ag/L in influent. Both freshly prepared Ag-NPs and aged Ag-NPs were tested with released silver ion as control. Results showed that Ag-NPs, especially freshly prepared Ag-NPs, can help to maintain or even increase the diversity of microbial community in activated sludge and the biomass concentration even under long-term treatment. It indicates that the hormesis model need to be considered for the toxicology of Ag-NPs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Unexpected Hydroxide Ion Structure and Properties at Low Hydration

Understanding the behavior of hydroxide ions in aqueous and non-aqueous media is fundamental to many chemical, biological, and electrochemical processes. Research has primarily focused on a single fully solvated hydroxide ion, either as an isolated cluster or in bulk. This work presents the first computational study to consider hydroxide under low hydration levels in detail, where the anion may not be fully solvated. Under such conditions, we find that the anions are predominantly present as unique water-bridged hydroxide pair complexes, distinct from previously reported structures under fully hydrated conditions. Although similar hydroxide pair structures were previously reported, we analyze these structures for the first time in the disordered liquid state where they are found to be unusually stable in the presence of bulky quaternary ammonium cations. Our findings help explain the unusual diffusion behavior as well as the higher reactivity of hydroxide anions observed under low hydration conditions.

computational studies↗
DOE OSTI2017

Biotemplated synthesis of inorganic materials: An emerging paradigm for nanomaterial synthesis inspired by nature

Biomineralization, the process by which biological systems direct the synthesis of inorganic structures from organic templates, is an exquisite example of nanomaterial self-assembly in nature. Its products include the shells of mollusks and the bones and teeth of vertebrates. By comparison, conventional inorganic synthesis techniques provide limited control over inorganic nanomaterial architecture. Inspired by biomineralization in nature, over the last two decades, the field of biotemplating has emerged as a new paradigm for inorganic nanomaterial assembly, wherein researchers seek to design novel nano-structures in which inorganic nanomaterial synthesis is directed from an underlying biomolecular template. Here, we review the motivation, mechanistic understanding, progress, and challenges for the field of biotemplating. We highlight the interdisciplinary nature of this field, and survey a broad range of examples of bio-templated engineering: ranging from strategies that exploit the inherent capabilities of proteins in nature, to genetically-engineered systems that unlock new capabilities for self-assembly with biomolecules. Here, we illustrate that the use of biological materials as templates for inorganic self-assembly holds tremendous potential for nanomaterial engineering, with applications that range from electronics and energy to medicine.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Biodegradation and flushing of MBT wastes

Highlights: • Stabilization was achieved for MBT wastes of different degrees of pretreatment. • About 92% reduction in the gas generation compared with raw MSW. • Pretreatment resulted in reduced TOC, nitrogen and heavy metals in leachate. • A large proportion of carbon and nitrogen remained in the waste material. - Abstract: Mechanical–biological treatment (MBT) processes are increasingly being adopted as a means of diverting biodegradable municipal waste (BMW) from landfill, for example to comply with the EU Landfill Directive. However, there is considerable uncertainty concerning the residual pollution potential of such wastes. This paper presents the results of laboratory experiments on two different MBT waste residues, carried out to investigate the remaining potential for the generation of greenhouse gases and the flushing of contaminants from these materials when landfilled. The potential for gas generation was found to be between 8% and 20% of that for raw MSW. Pretreatment of the waste reduced the potential for the release of organic carbon, ammoniacal nitrogen, and heavy metal contents into the leachate; and reduced the residual carbon remaining in the waste after final degradation from ∼320 g/kg dry matter for raw MSW to between 183 and 195 g/kg dry matter for the MBT wastes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Performance evaluation of a hybrid-passive landfill leachate treatment system using multivariate statistical techniques

Highlights: • Performance of a hybrid passive landfill leachate treatment system was evaluated. • 33 Water chemistry parameters were sampled for 21 months and statistically analyzed. • Parameters were strongly linked and explained most (>40%) of the variation in data. • Alkalinity, ammonia, COD, heavy metals, and iron were criteria for performance. • Eight other parameters were key in modeling system dynamics and criteria. - Abstract: A pilot-scale hybrid-passive treatment system operated at the Merrick Landfill in North Bay, Ontario, Canada, treats municipal landfill leachate and provides for subsequent natural attenuation. Collected leachate is directed to a hybrid-passive treatment system, followed by controlled release to a natural attenuation zone before entering the nearby Little Sturgeon River. The study presents a comprehensive evaluation of the performance of the system using multivariate statistical techniques to determine the interactions between parameters, major pollutants in the leachate, and the biological and chemical processes occurring in the system. Five parameters (ammonia, alkalinity, chemical oxygen demand (COD), “heavy” metals of interest, with atomic weights above calcium, and iron) were set as criteria for the evaluation of system performance based on their toxicity to aquatic ecosystems and importance in treatment with respect to discharge regulations. System data for a full range of water quality parameters over a 21-month period were analyzed using principal components analysis (PCA), as well as principal components (PC) and partial least squares (PLS) regressions. PCA indicated a high degree of association for most parameters with the first PC, which explained a high percentage (>40%) of the variation in the data, suggesting strong statistical relationships among most of the parameters in the system. Regression analyses identified 8 parameters (set as independent variables) that were most frequently retained for modeling the five criteria parameters (set as dependent variables), on a statistically significant level: conductivity, dissolved oxygen (DO), nitrite (NO{sub 2}{sup −}), organic nitrogen (N), oxidation reduction potential (ORP), pH, sulfate and total volatile solids (TVS). The criteria parameters and the significant explanatory parameters were most important in modeling the dynamics of the passive treatment system during the study period. Such techniques and procedures were found to be highly valuable and could be applied to other sites to determine parameters of interest in similar naturalized engineered systems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Phosphoketolase overexpression increases biomass and lipid yield from methane in an obligate methanotrophic biocatalyst

Microbial conversion of methane to high-value bio-based chemicals and materials offers a path to mitigate GHG emissions and valorize this abundant-yet -underutilized carbon source. In addition to fermentation optimization strategies, rational methanotrophic bacterial strain engineering offers a means to reach industrially relevant titers, carbon yields, and productivities of target products. The phosphoketolase pathway functions in heterofermentative bacteria where carbon flux through two sugar catabolic pathways to mixed acids (lactic acid and acetic acid) increases cellular ATP production. Importantly, this pathway also serves as an alternative route to produce acetyl-CoA that bypasses the CO 2 lost through pyruvate decarboxylation in the Embden-Meyerhof-Parnas pathway. Thus, the phosphoketolase pathway can be leveraged for carbon efficient biocatalysis to acetyl-CoA-derived intermediates and products. Here, we show that the industrially promising methane biocatalyst, Methylomicrobium buryatense , encodes two phosphoketolase isoforms that are expressed in methanol- and methane-grown cells. Overexpression of the PktB isoform led to a 2-fold increase in intracellular acetyl-CoA concentration, and a 2.6-fold yield enhancement from methane to microbial biomass and lipids compared to wild-type, increasing the potential for methanotroph lipid-based fuel production. Off-gas analysis and metabolite profiling indicated that global metabolic rearrangements, including significant increases in post-translational protein acetylation and gene expression of the tetrahydromethanopterin-linked pathway, along with decreases in several excreted products, coincided with the superior biomass and lipid yield observed in the engineered strain. Further, these data suggest that phosphoketolase may play a key regulatory role in methanotrophic bacterial metabolism. As a result, given that acetyl-CoA is a key intermediate in several biosynthetic pathways, phosphoketolase overexpression offers a viable strategy to enhance the economics of an array of biological methane conversion processes.

09 BIOMASS FUELS↗