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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Efficient secretion of a plastic degrading enzyme from the green algae Chlamydomonas reinhardtii

Abstract Plastic pollution has become a global crisis, with microplastics contaminating every environment on the planet, including our food, water, and even our bodies. In response, there is a growing interest in developing plastics that biodegrade naturally, thus avoiding the creation of persistent microplastics. As a mechanism to increase the rate of polyester plastic degradation, we examined the potential of using the green microalgaChlamydomonas reinhardtiifor the expression and secretion of PHL7, an enzyme that breaks down post-consumer polyethylene terephthalate (PET) plastics. We engineeredC. reinhardtiito secrete active PHL7 enzyme and selected strains showing robust expression, by using agar plates containing a polyester polyurethane (PU) dispersion as an efficient screening tool. This method demonstrated the enzyme’s efficacy in degrading ester bond-containing plastics, such as PET and bio-based polyurethanes, and highlights the potential for microalgae to be implemented in environmental biotechnology. The effectiveness of algal-expressed PHL7 in degrading plastics was shown by incubating PET with the supernatant from engineered strains, resulting in substantial plastic degradation, confirmed by mass spectrometry analysis of terephthalic acid formation from PET. Our findings demonstrate the feasibility of polyester plastic recycling using microalgae to produce plastic-degrading enzymes. This eco-friendly approach can support global efforts toward eliminating plastic in our environment, and aligns with the pursuit of low-carbon materials, as these engineered algae can also produce plastic monomer precursors. Finally, this data demonstratesC. reinhardtiicapabilities for recombinant enzyme production and secretion, offering a “green” alternative to traditional industrial enzyme production methods.

Science & Technology - Other Topics↗
DOE OSTI2021

Phenolic acid-degrading Paraburkholderia prime decomposition in forest soil

Abstract Plant-derived phenolic acids are catabolized by soil microorganisms whose activity may enhance the decomposition of soil organic carbon (SOC). We characterized whether phenolic acid-degrading bacteria enhance SOC mineralization in forest soils when primed with 13C-labeled p-hydroxybenzoic acid (pHB). We further tested whether pHB-induced priming could explain differences in SOC content among mono-specific tree plantations in a 70-year-old common garden experiment. pHB addition primed significant losses of SOC (3–13 µmols C g−1 dry wt soil over 7 days) compared to glucose, which reduced mineralization (-3 to -8 µmols C g−1 dry wt soil over 7 days). The principal degraders of pHB were Paraburkholderia and Caballeronia in all plantations regardless of tree species or soil type, with one predominant phylotype (RP11ASV) enriched 23-fold following peak pHB respiration. We isolated and confirmed the phenolic degrading activity of a strain matching this phylotype (RP11T), which encoded numerous oxidative enzymes, including secretion signal-bearing laccase, Dyp-type peroxidase and aryl-alcohol oxidase. Increased relative abundance of RP11ASV corresponded with higher pHB respiration and expression of pHB monooxygenase (pobA), which was inversely proportional to SOC content among plantations. pobA expression proved a responsive measure of priming activity. We found that stimulating phenolic-acid degrading bacteria can prime decomposition and that this activity, corresponding with differences in tree species, is a potential mechanism in SOC cycling in forests. Overall, this study highlights the ecology and function of Paraburkholderia whose associations with plant roots and capacity to degrade phenolics suggest a role for specialized bacteria in the priming effect.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Maximizing sunlight absorption in narrow bandgap semiconducting copper(I) iodides for enhanced photocatalytic dye degradation

Photocatalytic dye degradation leverages sunlight to break down dyes and pigments into safer, simpler molecules. Using a material that can absorb a broad range of the solar spectrum optimizes the speed and efficiency of this process. In this study, we explore a series of new, narrow bandgap copper iodide semiconductors (1.5–1.7 eV) with various dimensionalities (0D to 3D) to evaluate their photocatalytic efficiency in dye degradation. The most effective material achieved 95% degradation within just 27 minutes. Mass spectrometry provided a detailed insight and in-depth understanding into the degradation mechanism. All materials demonstrated excellent stability under ambient conditions, highlighting their promise as eco-friendly candidates for dye degradation in water purification.

Carignan, Gia M. [Rutgers Univ., Piscataway, NJ (U↗
DOE OSTI2023

Investigation of Nanoparticle Degradation in Hydrogen Fuel Cell Systems through Automated Electron Microscopy

Proton exchange membrane fuel cells (PEMFC) are promising devices for the deployment of hydrogen-powered heavy-duty vehicles, providing a higher efficiency for similar driving range and fueling time than the existing ones. However, PEMFCs still encounter durability challenges mainly due to catalyst degradation in the cathode. Mitigating these performance losses requires a better understanding of the degradation mechanisms under heavy-duty accelerated stress tests (ASTs) [1]. Scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) are key tools for the analysis of Pt and PtCo nanoparticle size, spatial distribution and composition [2]. Electron tomography is also used to determine the rate and type of degradation of catalyst nanoparticles as a function of their position on the carbon support. In this work, automated data acquisition software, paired with a custom Python code, have been used to study the effect of different accelerated stress tests (ASTs) on nanoparticle coarsening [2]. Figure 1 shows high-angle annular dark-field (HAADF)-STEM images and EDS maps comparing the cathodes of membrane electrode assemblies (MEAs) following an electrocatalyst AST performed under H2/N2 with that of the heavy-duty AST performed under H2/air. We will discuss how AST conditions affect considerably the spatial distribution of the nanoparticles across the electrode between the membrane and microporous layer. Although the median particle size increased more in the MEA aged under the heavy-duty AST, as determined using a high-throughput image analysis, the quantitative EDS measurements demonstrate that the electrocatalyst AST resulted in more Pt and Co dissolution from the cathode, which is another important indicator of electrocatalyst degradation. We will further present the impact of the relative humidity (% RH) on the degradation mechanisms demonstrated using the same approach. Electron tomography has been used to distinguish the Pt nanoparticles residing on the carbon support surface (exterior) from those within the pore structure (interior) in order to determine the relative stability of interior and exterior nanoparticles. As shown in Figure 2, we will compare the Pt catalyst particle size at the beginning of test (BOT) and end of test (EOT), and discuss the importance of automating the electron tomography workflow, i.e. acquisition, reconstruction, and visualization, to increase sampling and determine the standard deviation of these measurement. The outlook for utilizing low-dose cryo-tomography for limiting damage to the catalyst, support, and especially proton-conducting ionomer will also be discussed [3].

Amichi, Lynda↗
DOE OSTI2024

Efficient secretion of a plastic degrading enzyme from the green algae Chlamydomonas reinhardtii

AbstractPlastic pollution has become a global crisis, with microplastics contaminating every environment on the planet, including our food, water, and even our bodies. In response, there is a growing interest in developing plastics that biodegrade naturally, thus avoiding the creation of persistent microplastics. As a mechanism to increase the rate of polyester plastic degradation, we examined the potential of using the green microalgaChlamydomonas reinhardtiifor the expression and secretion of PHL7, an enzyme that breaks down post-consumer polyethylene terephthalate (PET) plastics. We engineeredC. reinhardtiito secrete active PHL7 enzyme and selected strains showing robust expression, by using agar plates containing a polyester polyurethane (PU) dispersion as an efficient screening tool. This method demonstrated the enzyme’s efficacy in degrading ester bond-containing plastics, such as PET and bio-based polyurethanes, and highlights the potential for microalgae to be implemented in environmental biotechnology. The effectiveness of algal-expressed PHL7 in degrading plastics was shown by incubating PET with the supernatant from engineered strains, resulting in substantial plastic degradation, confirmed by mass spectrometry analysis of terephthalic acid (TPA) formation from PET. Our findings demonstrate the feasibility of polyester plastic recycling using microalgae to produce plastic-degrading enzymes. This eco-friendly approach can support global efforts toward eliminating plastic in our environment, and aligns with the pursuit of low-carbon materials, as these engineered algae can also produce plastic monomer precursors. Finally, this data demonstratesC. reinhardtiicapabilities for recombinant enzyme production and secretion, offering a “green” alternative to traditional industrial enzyme production methods.Graphical Abstract

Molino, João Vitor Dutra (ORCID:0000000324759807)↗
DOE OSTI2023

A Real-Time Degradation Estimation Approach for Batteries in PV and Battery Hybrid Plant Operation

Conventional cyclic degradation assessment for batteries is often limited in its ability to provide real-time degradation information during operation, because the estimation of degradation is commonly performed after a specific evaluation period. Modified methods can provide real-time evaluation but at the cost of high computation complexity. This paper proposes a novel estimation method that addresses these limitations. It efficiently determines the incremental degradation of any two consecutive state-of-charge (SOC) samples during battery operation, thus enabling real-time estimation. To validate the proposed method, measurement data from lithium-ion phosphate (LFP) battery testing was adopted, and the results were compared with the conventional model and the measured capacity. The results demonstrate accuracy over the evaluation period in terms of cumulative degradation, and a reduced computation cost compared with other methods. This approach has benefits in various applications, especially in cases where batteries experience irregular charging and discharging stress cycles such as PV and battery hybrid plants.

Wang, Shumeng↗
DOE OSTI2020

Probing Membrane Degradation with Varying Catalyst Layer Thickness and Carbon Support

Understanding membrane degradation continues to be of significant importance when studying fuel cell durability. Fuel cell performance and durability depends heavily on the membrane's chemical and mechanical integrity. In Nafion® membranes, hydroxyl radicals are the primary cause of chemical membrane degradation as they attack the membrane's polymer structure. Radical formation can ensue via peroxide decomposition at the cathode or gases reacting on Pt particles within the membrane. Here, a previous research effort on membrane degradation as a function of ultra-low Pt loadings (≤ 0.1 mgPt cm -2 ) showed the degradation rate increases with Pt loading. This is most likely due to more heterogenous sites for radical formation. Manufacturing MEAs with ultra-low Pt loadings can yield thin, non-uniform catalyst layers. In this research effort we studied membrane degradation with ultra-low Pt loadings while varying catalyst layer thickness, I/C ratio, and types of carbon support.

25 ENERGY STORAGE↗
DOE OSTI2021

Investigation of Membrane Chemical Degradation as a Function of Catalyst Platinum Loading

Membrane chemical degradation is one of many factors that can impact fuel cell durability. Additionally, the fuel cell’s lifetime heavily depends on the membrane and its ability to maintain chemical and mechanical integrity. Previous studies indicate that chemical degradation is due to the formation of hydroxyl radicals that attack the polymer structure resulting in membrane thinning, pinhole formation, and the release of fluoride and sulfate ions. Membrane durability was investigated using ultra-low Pt electrode loadings (≤ 0.1 mg Pt cm -2 ). Accelerated stress testing (US-DOE protocols) demonstrated that the degradation rate was found to increase with higher Pt loadings. This is most likely due to more heterogeneous sites for radical formation due to hydrogen crossover to the cathode. We also explored membrane degradation rates while varying catalyst layer thickness, ionomer to carbon ratio, and types of carbon support. All of the aforementioned variables impact the membrane degradation rates.

25 ENERGY STORAGE↗
DOE OSTI2023

Characterization of Cycle-Aged Commercial NMC and NCA Lithium-ion Cells: I. Temperature-Dependent Degradation

Lithium-ion batteries are widely used in applications from consumer electronic devices to stationary energy storage. Appropriate management of batteries is challenging due to limited data on their performance and materials degradation. Previous studies have focused on characterization of single cells under specific operating conditions. In the present work, commercial 18650 lithium-ion cells with LiNi x Mn y Co 1-x-y O 2 (NMC) and LiNi x Co y Al 1-x-y O 2 (NCA) positive electrodes were characterized by a wide range of electrochemical and materials techniques after cycling at 15, 25, or 35 °C to ∼80% capacity. The NCA cells exhibit weak temperature dependence in their cycle aging and materials degradation. The NMC cells exhibited increased capacity fade and materials degradation as ambient temperature decreased. All cells exhibited loss of lithium inventory as their primary degradation mode. However, the NCA cells only showed evidence of solid electrolyte interphase (SEI) growth whereas the NMC cells showed signs of Li plating at 15 °C, transitioning to SEI growth at 35 °C. The NMC cells displayed signs of loss of active material at the positive electrode at lower temperatures, suggesting that Li plating is correlated to additional processes that increase the rate of degradation. These results highlight the importance of avoiding broad generalizations about Li-ion battery temperature dependence.

25 ENERGY STORAGE↗
DOE OSTI2023

Degradation of Ta 2 O 5 / SiO 2 dielectric cavity mirrors in ultra-high vacuum

In order for optical cavities to enable strong light-matter interactions for quantum metrology, networking, and scalability in quantum computing systems, their mirrors must have minimal losses. However, high-finesse dielectric cavity mirrors can degrade in ultra-high vacuum (UHV), increasing the challenges of upgrading to cavity-coupled quantum systems. We observe the optical degradation of high-finesse dielectric optical cavity mirrors after high-temperature UHV bake in the form of a substantial increase in surface roughness. We provide an explanation of the degradation through atomic force microscopy (AFM), X-ray fluorescence (XRF), selective wet etching, and optical measurements. We find the degradation is explained by oxygen reduction in Ta 2 O 5 followed by growth of tantalum sub-oxide defects with height to width aspect ratios near ten. We discuss the dependence of mirror loss on surface roughness and finally give recommendations to avoid degradation to allow for quick adoption of cavity-coupled systems.

Optics↗
DOE OSTI2020

Biotic degradation of acetonitrile. Limitations, controls and conversion rates

This document has been prepared to support Washington River Protection Solutions (WRPS) in their evaluation of technologies to remediate organic compounds in the Liquid Effluent Retention Facility (LERF)/Effluent Treatment Facility (ETF) during direct feed low activity waste (DFLAW) operations at Hanford. This report summarizes the results of a review of the available literature describing aerobic and anaerobic biological treatment of acetonitrile and proposes a test matrix to evaluate microbial degradation rates of acetonitrile. Numerous studies describe acetonitrile degradation by pure culture strains of bacteria, fungi, and yeast; however, the purpose of this review was to provide estimations of degradation under conditions that more closely approximate the Liquid Effluent Retention Facility (LERF) basins at the Hanford Site. To this end, documented limitations, controls, and conversion rates are summarized for mixed and natural microbial communities being maintained or operated as a biological treatment for wastewater processing. Based on the literature evaluation, the inherent capacity and rates of microbial degradation of acetonitrile are sufficiently high that if applied in the LERF basins, acetonitrile removal would be achieved. To be clear, though, published studies have not been conducted under conditions that approximate or that could be directly related to the LERF basins. Thus, a focused test matrix the encompasses LERF relevant conditions to specifically measure microbial degradation of acetonitrile is proposed and the results would provide the strong technical justification for use of this low-cost efficient biological process at LERF during DFLAW operations and beyond.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Fuel/Basket Degradation Modeling Summary

This report documents the activities in a preliminary phase of development for three models: 1) waste package breach model, 2) fuel/basket degradation model, and 3) dual-purpose canister (DPC) crush model. The waste package breach model describes the coupling of mass flow, heat transport, and canister shell deformation in response to a heat-generating (criticality) event. The fuel/basket degradation model describes potential weakening and disaggregation of the DPC structure from corrosion, possibly accelerated by seismic ground motion. Progressively degraded three-dimensional (3D) configurations of the fuel, basket, and shell are generated for future analysis of reactivity (with as-loaded DPC fuel characteristics). Another important application for the fuel/basket degradation model is validation of the two stylized degradation cases currently being used by other investigators for analysis of the as-loaded DPC inventory under disposal conditions. The DPC crush model investigates stability of a typical DPC after breach of the disposal overpack allows fluids from the repository near-field environment to penetrate and externally pressurize the canister shell. Preliminary results show that large deformation of the DPC could occur for external pressure on the order of 10 to 15 MPa, or the shell could be stable (not collapse) with pressure of 20 MPa or greater if the basket plates are fully welded at the connections.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Degradable Biocomposite Thermoplastic Polyurethanes

In this project, the team developed tough and degradable biocomposite thermoplastic polyurethanes (TPUs) by incorporating bacterial spores into TPUs as a biofunctional living filler. The team screened various bacteria and selected the Bacillus subtilis ATCC 6633 strain as the final candidate, primarily due to its genomic availability, sporulation ability and TPU assimilation activity. The heat-shock tolerance of ATCC 6633 spores was further improved through evolutionary engineering via Adaptive Laboratory Evolution (ALE), demonstrating a 17.7-fold enhanced germination efficiency post heat-shock treatment compared to the wild-type strain (WT). The team fabricated biocomposite TPUs by incorporating lyophilized powder of heat-shock tolerized (HST) spores during the hot melt extrusion (HME) of TPU at 135 °C. The baseline TPU used in this project is a commercially available soft-grade TPU (BCF45) manufactured by BASF. Colony forming unit (CFU) assays quantified that WT and HST spores in the TPU matrix retained approximately 20% and 100% survivability, respectively, after HME. Tensile testing demonstrated that the spores behaved as a polymer-reinforcing filler, positively affecting the overall tensile properties of the biocomposite TPU. For example, biocomposite TPU with WT and HST spores (BC TPU WT and BC TPU HST , respectively) exhibited up to 25% and 37% improved toughness, respectively, compared to TPU without spores. BC TPU HST showed remarkably improved disintegration in autoclaved compost (92% mass loss in 5 months), which simulated a microbially poor environment for TPU degradation. When compared to TPU without spores (44% mass loss in 5 months) the acceleration of degradation is marked. Respirometry confirmed that 72% of BC TPU HST was biomineralized into CO2 within 6 months, indicating that spores in the biocomposite TPU were germinated by utilizing nutrients in the autoclaved compost, facilitating TPU degradation at the end of the material's life. The team demonstrated the scale-up of biocomposite TPU fabrication using continuous extrusion and injection molding techniques. Processing conditions optimized in a lab-scale microcompounder were successfully transferred to a continuous extruder with a 30-fold increased throughput. Biocomposite TPUs prepared using these industry-relevant processes showed comparable toughness improvements to samples prepared in the lab-scale extruder. Excitingly, following compounding in the pilot-extruder the composite material could be injection molded, while retaining high spore viability and similar toughness improvements. The team also found that spores in biocomposite TPU served as antioxidants, preventing toughness decay during the recycled extrusion of BC TPU HST . Long-term storage tests over one year showed that the addition of spores had no negative effect on the longevity of the TPU. Furthermore, the team demonstrated the fabrication of spore-bearing biocomposite polymers with other polyesters such as PBAT, PLA, and PCL. We obtained promising preliminary data that showed overall toughness improvements for all polymers with spore addition. Finally, life cycle assessment (LCA) and techno-economic analysis (TEA) were carried out, which indicated minimal additional cost of fabrication. Overall, a tough and degradable biocomposite thermoplastic was successfully developed through this project, with all tasks completed successfully, achieving >100% of the objectives.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Properties, Physiological Functions and Involvement of Basidiomycetous Alcohol Oxidase in Wood Degradation

Extensive research efforts have been devoted to describing yeast alcohol oxidase (AO) and its promoter region, which is vastly applied in studies of heterologous gene expression. However, little is known about basidiomycetous AO and its physiological role in wood degradation. This review describes several alcohol oxidases from both white and brown rot fungi, highlighting their physicochemical and kinetic properties. Moreover, the review presents a detailed analysis of available AO-encoding gene promoter regions in basidiomycetous fungi with a discussion of the manipulations of culture conditions in relation to the modification of alcohol oxidase gene expression and changes in enzyme production. The analysis of reactions catalyzed by lignin-modifying enzymes (LME) and certain lignin auxiliary enzymes (LDA) elucidated the possible involvement of alcohol oxidase in the degradation of derivatives of this polymer. Combined data on lignin degradation pathways suggest that basidiomycetous AO is important in secondary reactions during lignin decomposition by wood degrading fungi. With numerous alcoholic substrates, the enzyme is probably engaged in a variety of catalytic reactions leading to the detoxification of compounds produced in lignin degradation processes and their utilization as a carbon source by fungal mycelium.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Diversity and Distribution of Hydrocarbon-Degrading Genes in the Cold Seeps from the Mediterranean and Caspian Seas

Marine cold seeps are unique ecological niches characterized by the emergence of hydrocarbons, including methane, which fosters diverse microbial communities. This study investigates the diversity and distribution of hydrocarbon-degrading genes and organisms in sediments from the Caspian and Mediterranean Seas, utilizing 16S rRNA and metagenomic sequencing to elucidate microbial community structure and functional potential. Our findings reveal distinct differences in hydrocarbon degrading gene profiles between the two seas, with pathways for aerobic and anaerobic hydrocarbon degradation co-existing in sediments from both basins. Aerobic pathways predominate in the surface sediments of the Mediterranean Sea, while anaerobic pathways are favored in the surface sediments of the anoxic Caspian Sea. Additionally, sediment depths significantly influence microbial diversity, with variations in gene abundance and community composition observed at different depths. Aerobic hydrocarbon-degrading genes decrease in diversity with depth in the Mediterranean Sea, whereas the diversity of aerobic hydrocarbon-degrading genes increases with depth in the Caspian Sea. These results enhance our understanding of microbial ecology in cold seep environments and have implications for bioremediation practices targeting hydrocarbon pollutants in marine ecosystems.

Microbiology↗
DOE OSTI2022

Module-Level Solutions For Degradation by Ionization Damage

After years of improving module efficiency while targeting mean degradation rates of 0.5 to 0.6 %/y for crystalline silicon technology, there is much evidence that the degradation rates are now increasing significantly. Contributing factors include:Radiation damage (UV-Light Induced Degradation): Trina solar: -4.5%/y degradation rate in Singapore, DOE National Laboratory Regional Test Centers showed degradation of -1% < r < -2%/y in crystalline silicon modules, Jinko Solar: -4% < r < -7% efficiency loss from 540 MJ/m-2 of UV-A light, ISFH: 15% relative power loss during of 1.8 GJ/m-2 UV exposure, attributed to H+. Electrical bias from positive system voltage (e.g., +1000 V, +1500 V) can drive ions and metallization through the encapsulation, NREL: Ion transport can affect the cell passivation, resulting in power loss of 5% to 40% in p-PERC+ (bifacial), NREL: Damage at cell rear with up to 17% power at cell fronts in n-PERT modules. Delamination can also occur due to cell surface reactions driven by light and bias.

module efficiency↗
DOE OSTI2023

Insight into the Radiolytic Degradation Mechanism of TODGA

Partitioning and transmutation schemes, where americium is separated from other components of used nuclear fuel and burned in a fast neutron reactor, offer a path to dramatically decrease the space requirements for storage of nuclear fuel cycle wastes, allowing more efficient usage of potentially scarce storage resources.[1] Improvements in the efficiency of processes for separating americium from used nuclear fuels can thus have a significant impact on the costs of future nuclear fuel cycles. Understanding separation ligand radiation chemistry is important for development of new ligands and processes, as the ligand degradation products can have a deleterious effect on a separation process. Tetraoctyl diglycolamide (TODGA) has been studied as a ligand for lanthanide/minor actinide extraction for partitioning and transmutation schemes. However, the mechanism of initial energy transfer from products of solvent radiolysis to TODGA is still under debate. One proposed mechanism is attack by a n-dodecane radical cation resulting in electron abstraction and formation of a TODGA radical cation,[2] while later work has proposed hydrogen abstraction from sites adjacent to the central ether oxygen by other radical species.[3] The latter mechanism is proposed to result in degradation products from rupture of the ether bond. However, radiolytic degradation of TODGA in n-dodecane shows products that would result from rupture of all the backbone bonds. There is little information on what degradation products would be expected to form from the TODGA radical cation. In this work, we have begun to investigate this by examining the electron impact (EI) ionization mass spectrum of TODGA, which initially produces a TODGA radical cation in the gas phase. The EI spectrum shows fragments that would result from most backbone bond cleavages, similar to what is observed in the radiolysis of TODGA in n-dodecane. As the lifetime of the solvent radical cation decreases from n-dodecane to n-hexane,[4] irradiation of TODGA in n-hexane should have less solvent radical cations available for reaction with TODGA, and instead should favor reactions with longer-lived radicals. In contrast to n-dodecane, radiolytic degradation of TODGA in n-hexane produces only N,N-dioctylacetamide, which would result from rupture of the ether bond. The n-dodecane radical cation lifetime is long enough to produce TODGA radical cations but the n-hexane radical cation is mostly consumed before reaction with TODGA, so other radical processes that abstract hydrogen from TODGA dominate. This suggests that electron abstraction by the n-dodecane radical cation is an important component of TODGA radiolysis, although it does not rule out the presence of mechanisms involving hydrogen abstraction adjacent to the ether oxygen. References [1] J. Serp et al., Energies 2017, 10 (9), DOI: 10.3390/en10091445. [2] C. Zarzana et al., Solvent Extr. Ion Exch. 2015, 33 (5), 431–447, DOI: 10.1080/07366299.2015.1012885. [3] T. Koubský et al., Prog. Nucl. Energy 2017, 94, 208–215, DOI: 10.1016/j.pnucene.2016.07.010. [4] F. Sviridenko et al., Chem. Phys. Lett. 1998, 297 (3), 343–349, DOI: 10.1016/S0009-2614(98)01099-9.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Removal of primary nutrient degraders reduces growth of soil microbial communities with genomic redundancy

Understanding how microorganisms within a soil community interact to support collective respiration and growth remains challenging. Here, we used a model substrate, chitin, and a synthetic Model Soil Consortium (MSC-2) to investigate how individual members of a microbial community contribute to decomposition and community growth. While MSC-2 can grow using chitin as the sole carbon source, we do not yet know how the growth kinetics or final biomass yields of MSC-2 vary when certain chitin degraders, or other important members, are absent. To characterize specific roles within this synthetic community, we carried out experiments leaving out members of MSC-2 and measuring biomass yields and CO 2 production. We chose two members to iteratively leave out (referred to by genus name): Streptomyces, as it is predicted via gene expression analysis to be a major chitin degrader in the community, and Rhodococcus as it is predicted via species co-abundance analysis to interact with several other members. Our results showed that when MSC-2 lacked Streptomyces, growth and respiration of the community was severely reduced. Removal of either Streptomyces or Rhodococcus led to major changes in abundance for several other species, pointing to a comprehensive shifting of the microbial community when important members are removed, as well as alterations in the metabolic profile, especially when Streptomyces was lacking. These results show that when keystone, chitin degrading members are removed, other members, even those with the potential to degrade chitin, do not fill the same metabolic niche to promote community growth. In addition, highly connected members may be removed with similar or even increased levels of growth and respiration. Our findings are critical to a better understanding of soil microbiology, specifically in how communities maintain activity when biotic or abiotic factors lead to changes in biodiversity in soil systems.

59 BASIC BIOLOGICAL SCIENCES↗