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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Characterization of Clostridium thermocellum strains with disrupted fermentation end-product pathways

Clostridium thermocellum is a thermophilic, cellulolytic anaerobe that is a candidate microorganism for industrial biofuels production. Strains with mutations in genes associated with production of L-lactate (Dldh) and/or acetate (Dpta) were characterized to gain insight into the intracellular processes that convert cellobiose to ethanol and other fermentation end-products. Cellobiose-grown cultures of the Dldh strain had identical biomass accumulation, fermentation end-products, transcription profile, and intracellular metabolite concentrations compared to its parent strain (DSM1313 Dhpt Dspo0A). The Dpta-deficient strain grew slower and had 30 % lower final biomass concentration compared to the parent strain, yet produced 75% more ethanol. A Dldh Dpta double-mutant strain evolved for faster growth had a growth rate and ethanol yield comparable to the parent strain, whereas its biomass accumulation was comparable to Dpta. Free amino acids were secreted by all examined strains, with both Dpta strains secreting higher amounts of alanine, valine, isoleucine, proline, glutamine, and threonine. Valine concentration for Dldh Dpta reached 5 mM by the end of growth, or 2.7 % of the substrate carbon utilized. These secreted amino acid concentrations correlate with increased intracellular pyruvate concentrations, up to sixfold in the Dpta and 16-fold in the Dldh Dpta strain. We hypothesize that the deletions in fermentation end-product pathways result in an intracellular redox imbalance, which the organism attempts to relieve, in part by recycling NADP* through increased production of amino acids.

Clostridium thermocellum↗
DOE OSTI2017

Biomanufacturing: history and perspective

Abstract Biomanufacturing is a type of manufacturing that utilizes biological systems (e.g., living microorganisms, resting cells, animal cells, plant cells, tissues, enzymes, or in vitro synthetic (enzymatic) systems) to produce commercially important biomolecules for use in the agricultural, food, material, energy, and pharmaceutical industries. History of biomanufacturing could be classified into the three revolutions in terms of respective product types (mainly), production platforms, and research technologies. Biomanufacturing 1.0 focuses on the production of primary metabolites (e.g., butanol, acetone, ethanol, citric acid) by using mono-culture fermentation; biomanufacturing 2.0 focuses on the production of secondary metabolites (e.g., penicillin, streptomycin) by using a dedicated mutant and aerobic submerged liquid fermentation; and biomanufacturing 3.0 focuses on the production of large-size biomolecules—proteins and enzymes (e.g., erythropoietin, insulin, growth hormone, amylase, DNA polymerase) by using recombinant DNA technology and advanced cell culture. Biomanufacturing 4.0 could focus on new products, for example, human tissues or cells made by regenerative medicine, artificial starch made by in vitro synthetic biosystems, isobutanol fermented by metabolic engineering, and synthetic biology-driven microorganisms, as well as exiting products produced by far better approaches. Biomanufacturing 4.0 would help address some of the most important challenges of humankind, such as food security, energy security and sustainability, water crisis, climate change, health issues, and conflict related to the energy, food, and water nexus.

Zhang, Yi-Heng Percival↗
DOE OSTI2019

Rational development of transformation in Clostridium thermocellum ATCC 27405 via complete methylome analysis and evasion of native restriction–modification systems

A major barrier to both metabolic engineering and fundamental biological studies is the lack of genetic tools in most microorganisms. One example is Clostridium thermocellum ATCC 27405 T , where genetic tools are not available to help validate decades of hypotheses. A crucial barrier to DNA transformation is restriction–modification systems, which defend against foreign DNA methylated differently than the host. To determine the active restriction–modification systems in this strain, we performed complete methylome analysis via single-molecule, real-time sequencing to detect 6-methyladenine and 4-methylcytosine and the rarely used whole-genome bisulfite sequencing to detect 5-methylcytosine. Multiple active systems were identified, and corresponding DNA methyltransferases were expressed from the Escherichia coli chromosome to mimic the C. thermocellum methylome. Plasmid methylation was experimentally validated and successfully electroporated into C. thermocellum ATCC 27405. This combined method enabled genetic modification of the C. thermocellum -type strain and acts as a blueprint for transformation of other non-model microorganisms.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Bioactivity Potentials of Biodegradable Chitosan/Gelatin Film Forming Solutions Combined with Monoterpenoid Compounds

Novel food packaging systems including biodegradable/edible films have been introduced to the market for consumers who desire natural products for their nutrition. Biochemically active plant compounds are added to the biopolymer-based films to improve their functionality. Within the present study, chitosan (1%) and gelatin (4%) biopolymer-based film forming solutions (FFSs) combined with 1, 2, 5 and 10% (v/v) eugenol, pulegone and carvacrol, monoterpenoid compounds, were evaluated for their antimicrobial and antioxidative potential. Antioxidant activities and total phenolic contents (TPC) of the FFSs were determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity and Folin–Ciocalteau assays, respectively. Screening the antimicrobial activity of FFSs were performed against food spoilage microorganisms including Bacillus cereus, Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes and a fungi, Candida albicans by using agar well diffusion method. The chitosan FFS containing 10% carvacrol had greater TPC (3857.3 ± 0.07 mg gallic acid equivalent/L). The highest antioxidative capacity was observed for the chitosan FFS containing 10% eugenol as 97.92 ± 0.01%. FFSs with monoterpenoids showed promising antimicrobial activities against tested microorganisms. Based on antioxidative and antimicrobial potentials of the FFSs, it can be envisaged to use monoterpenoid incorporation to biopolymer films for food packaging applications.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Galactomannan degradation by thermophilic enzymes: a hot topic for biotechnological applications

Extremophilic microorganisms are valuable sources of enzymes for various industrial applications. In fact, given their optimal catalytic activity and operational stability under harsh physical and chemical conditions, they represent a suitable alternative to their mesophilic counterparts. For instance, extremophilic enzymes are important to foster the switch from fossil-based to lignocellulose-based industrial processes. Indeed, more stable enzymes are needed, because the conversion of the lignocellulosic biomass to a wide palette of value-added products requires extreme chemo-physical pre-treatments. Galactomannans are part of the hemicellulose fraction in lignocellulosic biomass. They are heteropolymers constituted by a $β$-1,4-linked mannan backbone substituted with side chains of α-1,6-linked galactose residues. Therefore, the joint action of different hydrolytic enzymes (i.e. $β$-mannanase, $β$-mannosidase and $α$-galactosidase) is needed to accomplish their complete hydrolysis. So far, numerous galactomannan-degrading enzymes have been isolated and characterized from extremophilic microorganisms. Besides applications in biorefinery, these biocatalysts are also useful to improve the quality (i.e. digestibility and prebiotic properties) of food and feed as well as in paper industries to aid the pulp bleaching process. In this review, an overview about the structure, function and applications of galactomannans is provided. Moreover, a survey of (hyper)-thermophilic galactomannans-degrading enzymes, mainly characterized in the last decade, has been carried out. These extremozymes are described in the light of their biotechnological application in industrial processes requiring harsh conditions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Imaginary admittance and charge transfer resistance correlate to the physiological status of Shewanella oneidensis cultures in real time

Monitoring microbial activity is essential for industrial and environmental applications to proceed efficiently. To minimize time and labor-intensive monitoring, a new paradigm is required for in-situ, real time analysis. Since bioconversion of organics is accomplished by microorganisms through the oxidation of feedstocks linked to the reduction of electron acceptors, microorganisms can be viewed as electrochemical catalysts. In this respect, cell membranes have an electrical potential, which is analogous to a conventional capacitor and linked dynamically to cellular activity. Here, in this study, we demonstrate the use of electrochemical impedance spectrometry (EIS) and cyclic voltammetry (CV) for monitoring microbial metabolic activity in real time, in-situ. The effect of organic electron donors as a function of concentration to the physiological status of strains of Shewanella oneidensis was determined. In this study, the pyomelanin overproducer (S. oneidensis ΔhmgA) and the pyomelanin deficient mutant (S. oneidensis ΔmelA) were chosen due to different surface electrochemical characteristics along with differences in oxygen utilization efficiency. CV, relative admittance, phase shift and permittivity changed with growth status and correlated with electron flow from organic carbon sources and terminal electron acceptor availability. This work offers a novel and inexpensive approach to real time monitoring with the advantage of abundant data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Conversion of depolymerized sugars and aromatics from engineered feedstocks by two oleaginous red yeasts

One of the requirements for efficient biological conversion of lignocellulose to bioproducts is the compatibility of biological catalysts with the processes employed to solubilize and depolymerize the lignocellulosic components. The red yeasts Rhodosporidium toruloides and Rhodotorula mucilaginosa were evaluated for their ability to assimilate sugars and aromatic compounds extracted from two engineered lines of Arabidopsis thaliana with modified lignin or the wild-type using ionic liquid, acid or alkaline pretreatments. Differential amounts of monomeric sugars, organic acids and, in the case of the engineered lines, either 4-hydroxybenzoic or protocatechuic acid were additionally released from the biomass and found to be tolerated and consumed by both microorganisms. Genetically-engineered strains of the two red yeasts successfully converted the depolymerized products into the biofuel precursor bisabolene when cultivated on hydrolysates or synthetic media containing specific sugars, acids and aromatics found in the hydrolysates.

Rodriguez, Alberto↗
DOE OSTI2023

Rewiring metabolism of Clostridium thermocellum for consolidated bioprocessing of lignocellulosic biomass poplar to produce short-chain esters

Consolidated bioprocessing (CBP) of lignocellulosic biomass uses cellulolytic microorganisms to enable enzyme production, saccharification, and fermentation to produce biofuels, biochemicals, and biomaterials in a single step. However, understanding and redirecting metabolisms of these microorganisms compatible with CBP are limited. Here, a cellulolytic thermophile Clostridium thermocellum was engineered and demonstrated to be compatible with CBP integrated with a Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment for conversion of hardwood poplar into short-chain esters with industrial use as solvents, flavors, fragrances, and biofuels. The recombinant C. thermocellum engineered with deletion of carbohydrate esterases and stable overexpression of alcohol acetyltransferases improved ester production without compromised deacetylation activities. These esterases were discovered to exhibit promiscuous thioesterase activities and their deletion enhanced ester production by rerouting the electron and carbon metabolism. Ester production was further improved up to 80-fold and ester composition could be modulated by deleting lactate biosynthesis and using poplar with different pretreatment severity.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Bioconversion of natural gas to liquid fuel: Opportunities and challenges

Natural gas is a mixture of low molecular weight hydrocarbon gases that can be generated from either fossil or anthropogenic resources. Although natural gas is used as a transportation fuel, constraints in storage, relatively low energy content (MJ/L), and delivery have limited widespread adoption. Advanced utilization of natural gas has been explored for biofuel production by microorganisms. In recent years, the aerobic bioconversion of natural gas (or primarily the methane content of natural gas) into liquid fuels (Bio-GTL) by biocatalysts (methanotrophs) has gained increasing attention as a promising alternative for drop-in biofuel production. Methanotrophic bacteria are capable of converting methane into microbial lipids, which can in turn be converted into renewable diesel via a hydrotreating process. In this paper, biodiversity, catalytic properties and key enzymes and pathways of these microbes are summarized. Bioprocess technologies are discussed based upon existing literature, including cultivation conditions, fermentation modes, bioreactor design, and lipid extraction and upgrading. This review also outlines the potential of Bio-GTL using methane as an alternative carbon source as well as the major challenges and future research needs of microbial lipid accumulation derived from methane, key performance index, and techno-economic analysis. An analysis of raw material costs suggests that methane-derived diesel fuel has the potential to be competitive with petroleum-derived diesel. (C) 2014 The Authors. Published by Elsevier Inc.

Fei, Q↗
DOE OSTI2019

Computational Insights into Fuels and Chemicals Extraction from Microbial Biorefineries

Over the past two decades, substantial investments have been made in engineering microorganisms to produce specific fuels and chemicals as part of the global bioeconomy. Many target molecules accumulate intracellularly, and a challenge is how to effectively extract the product from the cells without needing to destroy them due to the barrier imposed by the cell membrane. For some hydrophobic compounds, an organic overlay is an effective strategy for nondestructive product extraction, although the relationship between functional groups on the product and the rate of extraction are not well understood. Through both biased and unbiased molecular dynamics simulations for a range of fatty acyl compounds and terpenoids, we directly compute permeability coefficients for different steps of the extraction process. Via comparative analysis between the calculated permeability coefficients and observed interactions between the compounds and the membrane, we determine how the rate limiting steps vary depending on product chemistry. For instance, fatty aldehydes are found to transfer very rapidly across the membrane bilayer relative to alcohols, although their comparable rate of extraction into the organic phase makes them equally effective at extraction from the cell. In assessing the terpenoids, it is found that in general a modestly hydrophilic product improves desorption rates into an organic phase sufficiently to make up for their lower bilayer crossing rate. With this new insight, we can more effectively engineer microorganisms towards the production of these modestly hydrophilic fuel precursors or chemicals.

09 BIOMASS FUELS↗
DOE OSTI2016

Computational design of microscopic swimmers and capsules: From directed motion to collective behavior

Systems of motile microscopic particles can exhibit behaviors that resemble those of living microorganisms, including cooperative motion, self-organization, and adaptability to changing environments. Using mesoscale computational modeling, we design synthetic microswimmers and microcapsules that undergo controllable, self-propelled motion in solution. Stimuli-responsive hydrogels are used to actuate the microswimmers and to enable their navigation and chemotaxing behavior. The self-propelled motion of microcapsules on solid surfaces is achieved by the release of encapsulated solutes that alter the surface adhesiveness. These signaling solutes also enable interactions among multiple microcapsules that lead to complex, cooperative behavior. Our findings provide guidelines for creating microscopic devices and machines able to autonomously move and mimic the communication and chemotaxis of biological microorganisms.

42 ENGINEERING↗
DOE OSTI2016

A superstructure-based framework for bio-separation network synthesis

Modern biotechnologies enable the production of chemicals using engineered microorganisms. However, the cost of downstream recovery and purification steps is high, which means that the feasibility of bio-based chemicals production depends heavily on the synthesis of cost-effective separation networks. To this end, we develop a superstructure-based framework for bio-separation network synthesis. Based on general separation principles and insights obtained from industrial processes for specific products, we first identify four separation stages: cell treatment, product phase isolation, concentration and purification, and refinement. For each stage, we systematically implement a set of connectivity rules to develop stage-superstructures, all of which are then integrated to generate a general superstructure that accounts for all types of chemicals that can be produced using microorganisms. Here we further develop a superstructure reduction method to solve specific instances, based on product attributes, technology availability, case-specific considerations, and final product stream specifications. A general optimization model, including short-cut models for all technologies, is formulated. The proposed framework enables preliminary synthesis and analysis of bio-separation networks, and thus estimation of separation costs.

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

Unlocking nature’s biosynthetic potential by directed genome evolution

Microorganisms have been increasingly explored as microbial cell factories for production of fuels, chemicals, drugs, and materials. Among the various metabolic engineering strategies, directed genome evolution has emerged as one of the most powerful tools to unlock the full biosynthetic potential of microorganisms. Furthermore we summarize the directed genome evolution strategies that have been developed in recent years, including adaptive laboratory evolution and various targeted genome-scale engineering strategies, and discuss their applications in basic and applied biological research.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Adsorption and intracellular uptake of mercuric mercury and methylmercury by methanotrophs and methylating bacteria

The cell surface adsorption and intracellular uptake of mercuric mercury Hg(II) and methylmercury (MeHg) are important in determining the fate and transformation of Hg in the environment. However, current information is limited about their interactions with two important groups of microorganisms, i.e., methanotrophs and Hg(II)-methylating bacteria, in aquatic systems. This study investigated the adsorption and uptake dynamics of Hg(II) and MeHg by three strains of methanotrophs, Methylomonas sp. strain EFPC3, Methylosinus trichosporium OB3b, and Methylococcus capsulatus Bath, and two Hg(II)-methylating bacteria, Pseudodesulfovibrio mercurii ND132 and Geobacter sulfurreducens PCA. Distinctive behaviors of these microorganisms towards Hg(II) and MeHg adsorption and intracellular uptake were observed. The methanotrophs took up 55–80% of inorganic Hg(II) inside cells after 24 h incubation, lower than methylating bacteria (>90%). Approximately 80–95% of MeHg was rapidly taken up by all the tested methanotrophs within 24 h. In contrast, after the same time, G. sulfurreducens PCA adsorbed 70% but took up <20% of MeHg, while P. mercurii ND132 adsorbed <20% but took up negligible amounts of MeHg. These results suggest that microbial surface adsorption and intracellular uptake of Hg(II) and MeHg depend on the specific types of microbes and appear to be related to microbial physiology that requires further detailed investigation. Despite being incapable of methylating Hg(II), methanotrophs play important roles in immobilizing both Hg(II) and MeHg, potentially influencing their bioavailability and trophic transfer. Furthermore, methanotrophs are not only important sinks for methane but also for Hg(II) and MeHg and can influence the global cycling of C and Hg.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Photocatalytic inactivation of Vibrio fischeri using Fe2O3-TiO2-based nanoparticles

Highlights: • A marine bacterium (Vibrio fisheri) was examined as biofilm forming microorganism. • The inactivation of bacteria was performed in saline and nutrient growth media. • The performance of five TiO{sub 2} based photocatalysts was investigated. • Effective inactivation of bacteria was achieved by visible light driven photocatalysts. Biofouling is a major problem in water membrane processes, especially in seawater reverse osmosis plants. Inactivation of Vibrio fischeri (a well-known marine bacterium forming biofilm) through photocatalysis via visible light was investigated in this work using active Fe{sub 2}O{sub 3}-TiO{sub 2} nanoparticles. Five Fe{sub 2}O{sub 3}-TiO{sub 2} photocatalysts with different weight percentage of Fe{sub 2}O{sub 3} (0–5 wt%) were synthesized using an ultrasonic-assisted co-precipitation method. The photocatalysts were characterized by powder X-ray diffraction (XRD), BET surface area, transmission electron Æ (TEM) plus selected area electron diffraction (SAED) patterns, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and diffuse-reflectance spectroscopy (DRS). Based on the design of experiments, the synthesized photocatalysts were tested for inactivation of V. fischeri under visible light irradiation at different temperatures (25–35 °C) and different photocatalyst dosage (0.1–2 g/L). The photocatalytic microbial inactivation experiments were performed in artificial seawater appropriate for growth of the marine bacterium. The results revealed that the highest inactivation efficiency of V. fischeri was achieved when 1 g/L of 2.5 wt% Fe{sub 2}O{sub 3}-TiO{sub 2} were used, at 35 °C. Photocatalytic inactivation of microorganisms using visible light-driven Fe{sub 2}O{sub 3}-TiO{sub 2} photocatalysts, could introduce an innovative green method in pretreatment units of reverse osmosis plants to control the membrane biofouling.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Hydrogel-assisted self-healing of biomineralized living building materials

Living building materials (LBMs) are an emergent class of structural materials that leverage the biomineralization capability of microorganisms within sand-hydrogel scaffolds to produce living, load-bearing structures. Here we produced LBMs using a physically crosslinkable sand-hydrogel scaffold and two microorganisms with different biomineralization pathways - Synechococcus sp. PCC 7002 (photosynthetic) and S. pasteurii (ureolytic) - and investigated their self-healing capacity. Our results reveal that both Synechococcus sp. PCC 7002 and S. pasteurii demonstrated exceptional viability within all LBMs for more than 20 days. Damaged LBMs containing Synechococcus sp. PCC 7002 exhibited 103% and 112% of their original compressive and flexural strengths, respectively, after three days of healing at 50% relative humidity (RH) (i.e., ambient conditions). In contrast, LBMs containing S. pasteurii exhibited 71% and 66% of their original compressive and flexural strengths, respectively, after three days of healing at 50% RH. The compressive and flexural strengths of all LBMs rebounded to 93-100% after seven days of healing at 50% RH. Data substantiate that the self-healing ability of the hydrogel plays a critical role in facilitating healing of LBMs, as evidenced by the 82-118% rebounds in compressive and flexural strengths by the sand-hydrogel scaffold alone after three or seven days of healing at 50% RH. Healing was less effective at 100% RH for all LBMs investigated herein.

36 MATERIALS SCIENCE↗