28 results on '"Gjersing E"'
Search Results
2. Chemically Specific Cellular Imaging of Biofilm Formation
- Author
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Herberg, J, primary, Schaldach, C, additional, Horn, J, additional, Gjersing, E, additional, and Maxwell, R, additional
- Published
- 2006
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3. Hierarchical dynamics of [As.sub.2][P.sub.2][S.sub.8] quasi-molecular units in a supercooled liquid in the As?P-S system: a 31P NMR spectroscopic study
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Gjersing, E. L., Sen, S., Maekawa, H., and Aitken, B. G.
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Sulfides -- Chemical properties ,Sulfides -- Thermal properties ,Supercooled liquids -- Chemical properties ,Arsenic -- Chemical properties ,Arsenic -- Thermal properties ,Nuclear magnetic resonance spectroscopy -- Usage ,Phosphorus compounds -- Chemical properties ,Phosphorus compounds -- Thermal properties ,Chemicals, plastics and rubber industries - Published
- 2009
4. Molecular Dynamics in Supercooled P−Se Liquids near the Glass Transition: Results from 31P NMR Spectroscopy
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Gjersing, E. L., primary, Sen, S., additional, and Aitken, B. G., additional
- Published
- 2011
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5. Mechanistic understanding of the effect of rigidity percolation on structural relaxation in supercooled germanium selenide liquids
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Gjersing, E. L., primary, Sen, S., additional, and Youngman, R. E., additional
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- 2010
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6. Structure, Connectivity, and Configurational Entropy of GexSe100−x Glasses: Results from 77Se MAS NMR Spectroscopy
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Gjersing, E. L., primary, Sen, S., additional, and Aitken, B. G., additional
- Published
- 2010
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7. Hierarchical Dynamics of As2P2S8 Quasi-Molecular Units in a Supercooled Liquid in the As−P−S System: A 31P NMR Spectroscopic Study
- Author
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Gjersing, E. L., primary, Sen, S., additional, Maekawa, H., additional, and Aitken, B. G., additional
- Published
- 2009
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8. Anomalously large decoupling of rotational and shear relaxation in a molecular glass
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Gjersing, E. L., primary, Sen, S., additional, Yu, P., additional, and Aitken, B. G., additional
- Published
- 2007
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9. Structure, Connectivity, and Configurational Entropy of GexSe100−xGlasses: Results from 77Se MAS NMR Spectroscopy
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Gjersing, E. L., Sen, S., and Aitken, B. G.
- Abstract
High-resolution 77Se MAS NMR spectroscopy has been conducted at 11.7 T to investigate the short-and intermediate- range structure and chemical order in binary GexSe100−xglasses with 5 ≤ x≤ 33.33. Four distinct Se environments are observed for the first time, corresponding to Se−Se−Se and Ge−Se−Se linkages as well as Ge−Se−Ge sites where the Se atom is shared by two GeSe4tetrahedra in either corner-sharing or edge-sharing configuration. Assignments of corner and edge-shared tetrahedra were made based on the 77Se MAS NMR spectrum of crystalline β-GeSe2. Analysis of the compositional variation of the relative concentrations of these Se sites indicates that the structure of GexSe100−xglasses in this composition range can be described as a randomly interconnected network of GeSe4tetrahedra and chains of Se atoms. The implications of this structural model are discussed in relation to the composition dependence of the glass-forming ability and kinetic fragility of the corresponding parent liquids.
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- 2010
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10. Magnetic resonance flow velocity and temperature mapping of a shape memory polymer foam device
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Wilson Thomas S, Herberg Julie L, Gjersing Erica, Small Ward, and Maitland Duncan J
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Medical technology ,R855-855.5 - Abstract
Abstract Background Interventional medical devices based on thermally responsive shape memory polymer (SMP) are under development to treat stroke victims. The goals of these catheter-delivered devices include re-establishing blood flow in occluded arteries and preventing aneurysm rupture. Because these devices alter the hemodynamics and dissipate thermal energy during the therapeutic procedure, a first step in the device development process is to investigate fluid velocity and temperature changes following device deployment. Methods A laser-heated SMP foam device was deployed in a simplified in vitro vascular model. Magnetic resonance imaging (MRI) techniques were used to assess the fluid dynamics and thermal changes associated with device deployment. Results Spatial maps of the steady-state fluid velocity and temperature change inside and outside the laser-heated SMP foam device were acquired. Conclusions Though non-physiological conditions were used in this initial study, the utility of MRI in the development of a thermally-activated SMP foam device has been demonstrated.
- Published
- 2009
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11. Compensatory Guaiacyl Lignin Biosynthesis at the Expense of Syringyl Lignin in 4CL1 -Knockout Poplar.
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Tsai CJ, Xu P, Xue LJ, Hu H, Nyamdari B, Naran R, Zhou X, Goeminne G, Gao R, Gjersing E, Dahlen J, Pattathil S, Hahn MG, Davis MF, Ralph J, Boerjan W, and Harding SA
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- Carboxy-Lyases genetics, Carboxy-Lyases metabolism, Catalysis, Gene Expression Regulation, Plant, Plants, Genetically Modified genetics, Xylem genetics, Lignin metabolism, Plants, Genetically Modified metabolism, Populus metabolism, Xylem metabolism
- Abstract
The lignin biosynthetic pathway is highly conserved in angiosperms, yet pathway manipulations give rise to a variety of taxon-specific outcomes. Knockout of lignin-associated 4 - coumarate : CoA ligases ( 4CLs ) in herbaceous species mainly reduces guaiacyl (G) lignin and enhances cell wall saccharification. Here we show that CRISPR-knockout of 4CL1 in poplar ( Populus tremula × alba ) preferentially reduced syringyl (S) lignin, with negligible effects on biomass recalcitrance. Concordant with reduced S-lignin was downregulation of ferulate 5 - hydroxylases ( F5Hs ). Lignification was largely sustained by 4CL5, a low-affinity paralog of 4CL1 typically with only minor xylem expression or activity. Levels of caffeate, the preferred substrate of 4CL5, increased in line with significant upregulation of caffeoyl shikimate esterase1 Upregulation of caffeoyl - CoA O - methyltransferase1 and downregulation of F5Hs are consistent with preferential funneling of 4CL5 products toward G-lignin biosynthesis at the expense of S-lignin. Thus, transcriptional and metabolic adaptations to 4CL1 -knockout appear to have enabled 4CL5 catalysis at a level sufficient to sustain lignification. Finally, genes involved in sulfur assimilation, the glutathione-ascorbate cycle, and various antioxidant systems were upregulated in the mutants, suggesting cascading responses to perturbed thioesterification in lignin biosynthesis., (© 2020 American Society of Plant Biologists. All Rights Reserved.)
- Published
- 2020
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12. Improving wood properties for wood utilization through multi-omics integration in lignin biosynthesis.
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Wang JP, Matthews ML, Williams CM, Shi R, Yang C, Tunlaya-Anukit S, Chen HC, Li Q, Liu J, Lin CY, Naik P, Sun YH, Loziuk PL, Yeh TF, Kim H, Gjersing E, Shollenberger T, Shuford CM, Song J, Miller Z, Huang YY, Edmunds CW, Liu B, Sun Y, Lin YJ, Li W, Chen H, Peszlen I, Ducoste JJ, Ralph J, Chang HM, Muddiman DC, Davis MF, Smith C, Isik F, Sederoff R, and Chiang VL
- Subjects
- Gene Expression Regulation, Plant, Plants, Genetically Modified genetics, Populus metabolism, Transcriptome genetics, Trees genetics, Trees metabolism, Xylem metabolism, Lignin biosynthesis, Lignin genetics, Populus genetics, Wood chemistry, Wood physiology
- Abstract
A multi-omics quantitative integrative analysis of lignin biosynthesis can advance the strategic engineering of wood for timber, pulp, and biofuels. Lignin is polymerized from three monomers (monolignols) produced by a grid-like pathway. The pathway in wood formation of Populus trichocarpa has at least 21 genes, encoding enzymes that mediate 37 reactions on 24 metabolites, leading to lignin and affecting wood properties. We perturb these 21 pathway genes and integrate transcriptomic, proteomic, fluxomic and phenomic data from 221 lines selected from ~2000 transgenics (6-month-old). The integrative analysis estimates how changing expression of pathway gene or gene combination affects protein abundance, metabolic-flux, metabolite concentrations, and 25 wood traits, including lignin, tree-growth, density, strength, and saccharification. The analysis then predicts improvements in any of these 25 traits individually or in combinations, through engineering expression of specific monolignol genes. The analysis may lead to greater understanding of other pathways for improved growth and adaptation.
- Published
- 2018
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13. Network-based integration of systems genetics data reveals pathways associated with lignocellulosic biomass accumulation and processing.
- Author
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Mizrachi E, Verbeke L, Christie N, Fierro AC, Mansfield SD, Davis MF, Gjersing E, Tuskan GA, Van Montagu M, Van de Peer Y, Marchal K, and Myburg AA
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- Carbon metabolism, Cell Wall metabolism, Chromosome Mapping, Crosses, Genetic, Eucalyptus genetics, Eucalyptus growth & development, Gene Expression Regulation, Plant, Hybridization, Genetic, Plant Proteins genetics, Plant Proteins metabolism, Quantitative Trait Loci, Wood metabolism, Biomass, Eucalyptus metabolism, Gene Regulatory Networks, Genes, Plant, Lignin metabolism, Metabolic Networks and Pathways genetics, Models, Genetic
- Abstract
As a consequence of their remarkable adaptability, fast growth, and superior wood properties, eucalypt tree plantations have emerged as key renewable feedstocks (over 20 million ha globally) for the production of pulp, paper, bioenergy, and other lignocellulosic products. However, most biomass properties such as growth, wood density, and wood chemistry are complex traits that are hard to improve in long-lived perennials. Systems genetics, a process of harnessing multiple levels of component trait information (e.g., transcript, protein, and metabolite variation) in populations that vary in complex traits, has proven effective for dissecting the genetics and biology of such traits. We have applied a network-based data integration (NBDI) method for a systems-level analysis of genes, processes and pathways underlying biomass and bioenergy-related traits using a segregating Eucalyptus hybrid population. We show that the integrative approach can link biologically meaningful sets of genes to complex traits and at the same time reveal the molecular basis of trait variation. Gene sets identified for related woody biomass traits were found to share regulatory loci, cluster in network neighborhoods, and exhibit enrichment for molecular functions such as xylan metabolism and cell wall development. These findings offer a framework for identifying the molecular underpinnings of complex biomass and bioprocessing-related traits. A more thorough understanding of the molecular basis of plant biomass traits should provide additional opportunities for the establishment of a sustainable bio-based economy., Competing Interests: The authors declare no conflict of interest.
- Published
- 2017
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14. An In-Depth Understanding of Biomass Recalcitrance Using Natural Poplar Variants as the Feedstock.
- Author
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Meng X, Pu Y, Yoo CG, Li M, Bali G, Park DY, Gjersing E, Davis MF, Muchero W, Tuskan GA, Tschaplinski TJ, and Ragauskas AJ
- Subjects
- Biotechnology, Cellulose chemistry, Hydrolysis, Lignin chemistry, Polymerization, Populus growth & development, Biofuels, Biomass, Populus chemistry
- Abstract
In an effort to better understand the biomass recalcitrance, six natural poplar variants were selected as feedstocks based on previous sugar release analysis. Compositional analysis and physicochemical characterizations of these poplars were performed and the correlations between these physicochemical properties and enzymatic hydrolysis yield were investigated. Gel permeation chromatography (GPC) and
13 C solid state NMR were used to determine the degree of polymerization (DP) and crystallinity index (CrI) of cellulose, and the results along with the sugar release study indicated that cellulose DP likely played a more important role in enzymatic hydrolysis. Simons' stain revealed that the accessible surface area of substrate significantly varied among these variants from 17.3 to 33.2 mg g-1biomass as reflected by dye adsorption, and cellulose accessibility was shown as one of the major factors governing substrates digestibility. HSQC and31 P NMR analysis detailed the structural features of poplar lignin variants. Overall, cellulose relevant factors appeared to have a stronger correlation with glucose release, if any, than lignin structural features. Lignin structural features, such as a phenolic hydroxyl group and the ratio of syringyl and guaiacyl (S/G), were found to have a more convincing impact on xylose release. Low lignin content, low cellulose DP, and high cellulose accessibility generally favor enzymatic hydrolysis; however, recalcitrance cannot be simply judged on any single substrate factor., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
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15. Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass.
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Li M, Pu Y, Yoo CG, Gjersing E, Decker SR, Doeppke C, Shollenberger T, Tschaplinski TJ, Engle NL, Sykes RW, Davis MF, Baxter HL, Mazarei M, Fu C, Dixon RA, Wang ZY, Neal Stewart C Jr, and Ragauskas AJ
- Abstract
Background: The native recalcitrance of plants hinders the biomass conversion process using current biorefinery techniques. Down-regulation of the caffeic acid O -methyltransferase ( COMT ) gene in the lignin biosynthesis pathway of switchgrass reduced the thermochemical and biochemical conversion recalcitrance of biomass. Due to potential environmental influences on lignin biosynthesis and deposition, studying the consequences of physicochemical changes in field-grown plants without pretreatment is essential to evaluate the performance of lignin-altered plants. We determined the chemical composition, cellulose crystallinity and the degree of its polymerization, molecular weight of hemicellulose, and cellulose accessibility of cell walls in order to better understand the fundamental features of why biomass is recalcitrant to conversion without pretreatment. The most important is to investigate whether traits and features are stable in the dynamics of field environmental effects over multiple years., Results: Field-grown COMT down-regulated plants maintained both reduced cell wall recalcitrance and lignin content compared with the non-transgenic controls for at least 3 seasons. The transgenic switchgrass yielded 35-84% higher total sugar release (enzymatic digestibility or saccharification) from a 72-h enzymatic hydrolysis without pretreatment and also had a 25-32% increase in enzymatic sugar release after hydrothermal pretreatment. The COMT -silenced switchgrass lines had consistently lower lignin content, e.g., 12 and 14% reduction for year 2 and year 3 growing season, respectively, than the control plants. By contrast, the transgenic lines had 7-8% more xylan and galactan contents than the wild-type controls. Gel permeation chromatographic results revealed that the weight-average molecular weights of hemicellulose were 7-11% lower in the transgenic than in the control lines. In addition, we found that silencing of COMT in switchgrass led to 20-22% increased cellulose accessibility as measured by the Simons' stain protocol. No significant changes were observed on the arabinan and glucan contents, cellulose crystallinity, and cellulose degree of polymerization between the transgenic and control plants. With the 2-year comparative analysis, both the control and transgenic lines had significant increases in lignin and glucan contents and hemicellulose molecular weight across the growing seasons., Conclusions: The down-regulation of COMT in switchgrass resulting in a reduced lignin content and biomass recalcitrance is stable in a field-grown trial for at least three seasons. Among the determined affecting factors, the reduced biomass recalcitrance of the COMT -silenced switchgrass, grown in the field conditions for two and three seasons, was likely related to the decreased lignin content and increased biomass accessibility, whereas the cellulose crystallinity and degree of its polymerization and hemicellulose molecular weights did not contribute to the reduction of recalcitrance significantly. This finding suggests that lignin down-regulation in lignocellulosic feedstock confers improved saccharification that translates from greenhouse to field trial and that lignin content and biomass accessibility are two significant factors for developing a reduced recalcitrance feedstock by genetic modification.
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- 2017
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16. The effects of high concentrations of ionic liquid on GB1 protein structure and dynamics probed by high-resolution magic-angle-spinning NMR spectroscopy.
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Warner L, Gjersing E, Follett SE, Elliott KW, Dzyuba SV, and Varga K
- Abstract
Ionic liquids have great potential in biological applications and biocatalysis, as some ionic liquids can stabilize proteins and enhance enzyme activity, while others have the opposite effect. However, on the molecular level, probing ionic liquid interactions with proteins, especially in solutions containing high concentration of ionic liquids, has been challenging. In the present work the
13 C,15 N-enriched GB1 model protein was used to demonstrate applicability of high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy to investigate ionic liquid - protein interactions. Effect of an ionic liquid (1-butyl-3-methylimidazolium bromide, [C4 -mim]Br) on GB1was studied over a wide range of the ionic liquid concentrations (0.6 to 3.5 M, which corresponds to 10%-60% v/v). Interactions between GB1 and [C4 -mim]Br were observed from changes in the chemical shifts of the protein backbone as well as the changes in15 N ps-ns dynamics and rotational correlation times. Site-specific interactions between the protein and [C4 -mim]Br were assigned using 3D methods under HR-MAS conditions. Thus, HR-MAS NMR is a viable tool that could aid in elucidation of the molecular mechanism of ionic liquid - protein interactions.- Published
- 2016
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17. Knockdown of a laccase in Populus deltoides confers altered cell wall chemistry and increased sugar release.
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Bryan AC, Jawdy S, Gunter L, Gjersing E, Sykes R, Hinchee MA, Winkeler KA, Collins CM, Engle N, Tschaplinski TJ, Yang X, Tuskan GA, Muchero W, and Chen JG
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- Cell Wall enzymology, Cell Wall genetics, Gene Expression Regulation, Plant genetics, Laccase genetics, Lignin metabolism, Plants, Genetically Modified genetics, Xylose metabolism, Cell Wall chemistry, Laccase metabolism, Plants, Genetically Modified enzymology, Populus enzymology, Populus genetics
- Abstract
Plant laccases are thought to function in the oxidation of monolignols which leads to higher order lignin formation. Only a hand-full of laccases in plants have been functionally evaluated, and as such little is known about the breadth of their impact on cell wall chemistry or structure. Here, we describe a previously uncharacterized laccase from Populus, encoded by locus Potri.008G064000, whose reduced expression resulted in transgenic Populus trees with changes in syringyl/guaiacyl ratios as well as altered sugar release phenotypes. These phenotypes are consistent with plant biomass exhibiting reduced recalcitrance. Interestingly, the transgene effect on recalcitrance is dependent on a mild pretreatment prior to chemical extraction of sugars. Metabolite profiling suggests the transgene modulates phenolics that are associated with the cell wall structure. We propose that this particular laccase has a range of functions related to oxidation of phenolics and conjugation of flavonoids that interact with lignin in the cell wall., (© 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)
- Published
- 2016
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18. Biological lignocellulose solubilization: comparative evaluation of biocatalysts and enhancement via cotreatment.
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Paye JM, Guseva A, Hammer SK, Gjersing E, Davis MF, Davison BH, Olstad J, Donohoe BS, Nguyen TY, Wyman CE, Pattathil S, Hahn MG, and Lynd LR
- Abstract
Background: Feedstock recalcitrance is the most important barrier impeding cost-effective production of cellulosic biofuels. Pioneer commercial cellulosic ethanol facilities employ thermochemical pretreatment and addition of fungal cellulase, reflecting the main research emphasis in the field. However, it has been suggested that it may be possible to process cellulosic biomass without thermochemical pretreatment using thermophilic, cellulolytic bacteria. To further explore this idea, we examine the ability of various biocatalysts to solubilize autoclaved but otherwise unpretreated cellulosic biomass under controlled but not industrial conditions., Results: Carbohydrate solubilization of mid-season harvested switchgrass after 5 days ranged from 24 % for Caldicellulosiruptor bescii to 65 % for Clostridium thermocellum, with intermediate values for a thermophilic horse manure enrichment, Clostridium clariflavum, Clostridium cellulolyticum, and simultaneous saccharification and fermentation (SSF) featuring a fungal cellulase cocktail and yeast. Under a variety of conditions, solubilization yields were about twice as high for C. thermocellum compared to fungal cellulase. Solubilization of mid-season harvested switchgrass was about twice that of senescent switchgrass. Lower yields and greater dependence on particle size were observed for Populus as compared to switchgrass. Trends observed from data drawn from six conversion systems and three substrates, including both time course and end-point data, were (1) equal fractional solubilization of glucan and xylan, (2) no biological solubilization of the non-carbohydrate fraction of biomass, and (3) higher solubilization for three of the four bacterial cultures tested as compared to the fungal cellulase system. Brief (5 min) ball milling of solids remaining after fermentation of senescent switchgrass by C. thermocellum nearly doubled carbohydrate solubilization upon reinnoculation as compared to a control without milling. Greater particle size reduction and solubilization were observed for milling of partially fermented solids than for unfermented solids. Physical disruption of cellulosic feedstocks after initiation of fermentation, termed cotreatment, warrants further study., Conclusions: While the ability to achieve significant solubilization of minimally pretreated switchgrass is widespread, a fivefold difference between the most and least effective biocatalyst-feedstock combinations was observed. Starting with nature's best biomass-solubilizing systems may enable a reduction in the amount of non-biological processing required, and in particular substitution of cotreatment for pretreatment.
- Published
- 2016
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19. Phosphoketolase pathway contributes to carbon metabolism in cyanobacteria.
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Xiong W, Lee TC, Rommelfanger S, Gjersing E, Cano M, Maness PC, Ghirardi M, and Yu J
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- Acetates metabolism, Aldose-Ketose Isomerases genetics, Aldose-Ketose Isomerases metabolism, Bacterial Proteins genetics, Bacterial Proteins metabolism, Genetic Complementation Test, Heterotrophic Processes, Ketoglutaric Acids metabolism, Nitrogen metabolism, Pentosephosphates metabolism, Phosphotransferases (Alcohol Group Acceptor) genetics, Phosphotransferases (Alcohol Group Acceptor) metabolism, Synechocystis genetics, Xylose metabolism, Aldehyde-Lyases metabolism, Carbon metabolism, Synechocystis metabolism
- Abstract
Central carbon metabolism in cyanobacteria comprises the Calvin-Benson-Bassham (CBB) cycle, glycolysis, the pentose phosphate (PP) pathway and the tricarboxylic acid (TCA) cycle. Redundancy in this complex metabolic network renders the rational engineering of cyanobacterial metabolism for the generation of biomass, biofuels and chemicals a challenge. Here we report the presence of a functional phosphoketolase pathway, which splits xylulose-5-phosphate (or fructose-6-phosphate) to acetate precursor acetyl phosphate, in an engineered strain of the model cyanobacterium Synechocystis (ΔglgC/xylAB), in which glycogen synthesis is blocked, and xylose catabolism enabled through the introduction of xylose isomerase and xylulokinase. We show that this mutant strain is able to metabolise xylose to acetate on nitrogen starvation. To see whether acetate production in the mutant is linked to the activity of phosphoketolase, we disrupted a putative phosphoketolase gene (slr0453) in the ΔglgC/xylAB strain, and monitored metabolic flux using (13)C labelling; acetate and 2-oxoglutarate production was reduced in the light. A metabolic flux analysis, based on isotopic data, suggests that the phosphoketolase pathway metabolises over 30% of the carbon consumed by ΔglgC/xylAB during photomixotrophic growth on xylose and CO2. Disruption of the putative phosphoketolase gene in wild-type Synechocystis also led to a deficiency in acetate production in the dark, indicative of a contribution of the phosphoketolase pathway to heterotrophic metabolism. We suggest that the phosphoketolase pathway, previously uncharacterized in photosynthetic organisms, confers flexibility in energy and carbon metabolism in cyanobacteria, and could be exploited to increase the efficiency of cyanobacterial carbon metabolism and photosynthetic productivity.
- Published
- 2015
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20. High-throughput Screening of Recalcitrance Variations in Lignocellulosic Biomass: Total Lignin, Lignin Monomers, and Enzymatic Sugar Release.
- Author
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Decker SR, Sykes RW, Turner GB, Lupoi JS, Doepkke C, Tucker MP, Schuster LA, Mazza K, Himmel ME, Davis MF, and Gjersing E
- Subjects
- Carbohydrates chemistry, Chromatography, High Pressure Liquid methods, Glucose analysis, High-Throughput Screening Assays methods, Plants chemistry, Xylose analysis, Biomass, Carbohydrates analysis, Lignin chemistry
- Abstract
The conversion of lignocellulosic biomass to fuels, chemicals, and other commodities has been explored as one possible pathway toward reductions in the use of non-renewable energy sources. In order to identify which plants, out of a diverse pool, have the desired chemical traits for downstream applications, attributes, such as cellulose and lignin content, or monomeric sugar release following an enzymatic saccharification, must be compared. The experimental and data analysis protocols of the standard methods of analysis can be time-consuming, thereby limiting the number of samples that can be measured. High-throughput (HTP) methods alleviate the shortcomings of the standard methods, and permit the rapid screening of available samples to isolate those possessing the desired traits. This study illustrates the HTP sugar release and pyrolysis-molecular beam mass spectrometry pipelines employed at the National Renewable Energy Lab. These pipelines have enabled the efficient assessment of thousands of plants while decreasing experimental time and costs through reductions in labor and consumables.
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- 2015
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21. Evaluating lignocellulosic biomass, its derivatives, and downstream products with Raman spectroscopy.
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Lupoi JS, Gjersing E, and Davis MF
- Abstract
The creation of fuels, chemicals, and materials from plants can aid in replacing products fabricated from non-renewable energy sources. Before using biomass in downstream applications, it must be characterized to assess chemical traits, such as cellulose, lignin, or lignin monomer content, or the sugars released following an acid or enzymatic hydrolysis. The measurement of these traits allows researchers to gage the recalcitrance of the plants and develop efficient deconstruction strategies to maximize yields. Standard methods for assessing biomass phenotypes often have experimental protocols that limit their use for screening sizeable numbers of plant species. Raman spectroscopy, a non-destructive, non-invasive vibrational spectroscopy technique, is capable of providing qualitative, structural information and quantitative measurements. Applications of Raman spectroscopy have aided in alleviating the constraints of standard methods by coupling spectral data with multivariate analysis to construct models capable of predicting analytes. Hydrolysis and fermentation products, such as glucose and ethanol, can be quantified off-, at-, or on-line. Raman imaging has enabled researchers to develop a visual understanding of reactions, such as different pretreatment strategies, in real-time, while also providing integral chemical information. This review provides an overview of what Raman spectroscopy is, and how it has been applied to the analysis of whole lignocellulosic biomass, its derivatives, and downstream process monitoring.
- Published
- 2015
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22. Downregulation of GAUT12 in Populus deltoides by RNA silencing results in reduced recalcitrance, increased growth and reduced xylan and pectin in a woody biofuel feedstock.
- Author
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Biswal AK, Hao Z, Pattathil S, Yang X, Winkeler K, Collins C, Mohanty SS, Richardson EA, Gelineo-Albersheim I, Hunt K, Ryno D, Sykes RW, Turner GB, Ziebell A, Gjersing E, Lukowitz W, Davis MF, Decker SR, Hahn MG, and Mohnen D
- Abstract
Background: The inherent recalcitrance of woody bioenergy feedstocks is a major challenge for their use as a source of second-generation biofuel. Secondary cell walls that constitute the majority of hardwood biomass are rich in cellulose, xylan, and lignin. The interactions among these polymers prevent facile accessibility and deconstruction by enzymes and chemicals. Plant biomass that can with minimal pretreatment be degraded into sugars is required to produce renewable biofuels in a cost-effective manner., Results: GAUT12/IRX8 is a putative glycosyltransferase proposed to be involved in secondary cell wall glucuronoxylan and/or pectin biosynthesis based on concomitant reductions of both xylan and the pectin homogalacturonan (HG) in Arabidopsis irx8 mutants. Two GAUT12 homologs exist in Populus trichocarpa, PtGAUT12.1 and PtGAUT12.2. Knockdown expression of both genes simultaneously has been shown to reduce xylan content in Populus wood. We tested the proposition that RNA interference (RNAi) downregulation of GAUT12.1 alone would lead to increased sugar release in Populus wood, that is, reduced recalcitrance, based on the hypothesis that GAUT12 synthesizes a wall structure required for deposition of xylan and that cell walls with less xylan and/or modified cell wall architecture would have reduced recalcitrance. Using an RNAi approach, we generated 11 Populus deltoides transgenic lines with 50 to 67% reduced PdGAUT12.1 transcript expression compared to wild type (WT) and vector controls. Ten of the eleven RNAi lines yielded 4 to 8% greater glucose release upon enzymatic saccharification than the controls. The PdGAUT12.1 knockdown (PdGAUT12.1-KD) lines also displayed 12 to 52% and 12 to 44% increased plant height and radial stem diameter, respectively, compared to the controls. Knockdown of PdGAUT12.1 resulted in a 25 to 47% reduction in galacturonic acid and 17 to 30% reduction in xylose without affecting total lignin content, revealing that in Populus wood as in Arabidopsis, GAUT12 affects both pectin and xylan formation. Analyses of the sugars present in sequential cell wall extracts revealed a reduction of glucuronoxylan and pectic HG and rhamnogalacturonan in extracts from PdGAUT12.1-KD lines., Conclusions: The results show that downregulation of GAUT12.1 leads to a reduction in a population of xylan and pectin during wood formation and to reduced recalcitrance, more easily extractable cell walls, and increased growth in Populus.
- Published
- 2015
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23. Enhanced characteristics of genetically modified switchgrass (Panicum virgatum L.) for high biofuel production.
- Author
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Shen H, Poovaiah CR, Ziebell A, Tschaplinski TJ, Pattathil S, Gjersing E, Engle NL, Katahira R, Pu Y, Sykes R, Chen F, Ragauskas AJ, Mielenz JR, Hahn MG, Davis M, Stewart CN Jr, and Dixon RA
- Abstract
Background: Lignocellulosic biomass is one of the most promising renewable and clean energy resources to reduce greenhouse gas emissions and dependence on fossil fuels. However, the resistance to accessibility of sugars embedded in plant cell walls (so-called recalcitrance) is a major barrier to economically viable cellulosic ethanol production. A recent report from the US National Academy of Sciences indicated that, "absent technological breakthroughs", it was unlikely that the US would meet the congressionally mandated renewable fuel standard of 35 billion gallons of ethanol-equivalent biofuels plus 1 billion gallons of biodiesel by 2022. We here describe the properties of switchgrass (Panicum virgatum) biomass that has been genetically engineered to increase the cellulosic ethanol yield by more than 2-fold., Results: We have increased the cellulosic ethanol yield from switchgrass by 2.6-fold through overexpression of the transcription factor PvMYB4. This strategy reduces carbon deposition into lignin and phenolic fermentation inhibitors while maintaining the availability of potentially fermentable soluble sugars and pectic polysaccharides. Detailed biomass characterization analyses revealed that the levels and nature of phenolic acids embedded in the cell-wall, the lignin content and polymer size, lignin internal linkage levels, linkages between lignin and xylans/pectins, and levels of wall-bound fucose are all altered in PvMYB4-OX lines. Genetically engineered PvMYB4-OX switchgrass therefore provides a novel system for further understanding cell wall recalcitrance., Conclusions: Our results have demonstrated that overexpression of PvMYB4, a general transcriptional repressor of the phenylpropanoid/lignin biosynthesis pathway, can lead to very high yield ethanol production through dramatic reduction of recalcitrance. MYB4-OX switchgrass is an excellent model system for understanding recalcitrance, and provides new germplasm for developing switchgrass cultivars as biomass feedstocks for biofuel production.
- Published
- 2013
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24. Rapid determination of sugar content in biomass hydrolysates using nuclear magnetic resonance spectroscopy.
- Author
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Gjersing E, Happs RM, Sykes RW, Doeppke C, and Davis MF
- Subjects
- Chromatography, High Pressure Liquid methods, Hydrolysis, Time Factors, Biomass, Carbohydrates analysis, Cellulose metabolism, Magnetic Resonance Spectroscopy methods
- Abstract
Large populations of potential cellulosic biomass feedstocks are currently being screened for fuel and chemical applications. The monomeric sugar content, released through hydrolysis, is of particular importance and is currently measured with time-consuming HPLC methods. A method for sugar detection is presented here that employs (1)H NMR spectra regressed against primary HPLC sugar concentration data to build partial least squares (PLS) models. The PLS2 model is able to predict concentrations of both major sugar components, like glucose and xylose, and minor sugars, such as arabinose and mannose, in biomass hydrolysates. The model was built with 65 samples from a variety of different biomass species and covers a wide range of sugar concentrations. Model predictions were validated with a set of 15 samples which were all within error of both HPLC and NMR integration measurements. The data collection time for these NMR measurements is less than 20 min, offering a significant improvement to the 1 h acquisition time that is required for HPLC., (Copyright © 2012 Wiley Periodicals, Inc.)
- Published
- 2013
- Full Text
- View/download PDF
25. Solid-state selective (13)C excitation and spin diffusion NMR to resolve spatial dimensions in plant cell walls.
- Author
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Foston M, Katahira R, Gjersing E, Davis MF, and Ragauskas AJ
- Subjects
- Carbon Isotopes, Cellulose analysis, Cellulose chemistry, Lignin analysis, Lignin chemistry, Polysaccharides analysis, Polysaccharides chemistry, Zea mays chemistry, Cell Wall chemistry, Magnetic Resonance Spectroscopy, Plant Cells ultrastructure
- Abstract
The average spatial dimensions between major biopolymers within the plant cell wall can be resolved using a solid-state NMR technique referred to as a (13)C cross-polarization (CP) SELDOM (selectively by destruction of magnetization) with a mixing time delay for spin diffusion. Selective excitation of specific aromatic lignin carbons indicates that lignin is in close proximity to hemicellulose followed by amorphous and finally crystalline cellulose. (13)C spin diffusion time constants (T(SD)) were extracted using a two-site spin diffusion theory developed for (13)C nuclei under magic angle spinning (MAS) conditions. These time constants were then used to calculate an average lower-limit spin diffusion length between chemical groups within the plant cell wall. The results on untreated (13)C enriched corn stover stem reveal that the lignin carbons are, on average, located at distances ∼0.7-2.0 nm from the carbons in hemicellulose and cellulose, whereas the pretreated material had larger separations.
- Published
- 2012
- Full Text
- View/download PDF
26. Molecular dynamics in supercooled P-Se liquids near the glass transition: results from 31P NMR spectroscopy.
- Author
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Gjersing EL, Sen S, and Aitken BG
- Abstract
The structure of phosphorus selenide glasses with compositions close to the P(4)Se(3) stoichiometry with and without doping with a few atom % Ge has been investigated with Raman and (31)P NMR spectroscopic techniques. The results indicate that the structure of these glasses consists predominantly of P(4)Se(3) cage molecules. However, in spite of this structural similarity, doping with Ge results in a remarkably large increase in T(g). The dynamical behavior of the constituent P(4)Se(3) molecules in the Ge-free composition is investigated with a (31)P NMR hole-burning technique in the supercooled liquid state. These molecules perform large angle rotational reorientations near and above the glass transition with time scales similar to those expected for shear relaxation. Such coupling between molecular rotation and shear relaxation processes near T(g) is reminiscent of the dynamical behavior of organic molecular glass-forming liquids. However, this behavior is in stark contrast with the large temporal decoupling between molecular rotation and shear relaxation previously reported for a Ge-doped arsenic sulfide liquid that contained similarly structured As(4)S(3) cage molecules.
- Published
- 2011
- Full Text
- View/download PDF
27. Magnetic resonance flow velocity and temperature mapping of a shape memory polymer foam device.
- Author
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Small W 4th, Gjersing E, Herberg JL, Wilson TS, and Maitland DJ
- Subjects
- Isocyanates, Lasers, Materials Testing, Rheology, Cardiovascular Surgical Procedures instrumentation, Cyanates, Ethanolamines, Ethylenediamines, Magnetic Resonance Imaging, Polymers, Temperature
- Abstract
Background: Interventional medical devices based on thermally responsive shape memory polymer (SMP) are under development to treat stroke victims. The goals of these catheter-delivered devices include re-establishing blood flow in occluded arteries and preventing aneurysm rupture. Because these devices alter the hemodynamics and dissipate thermal energy during the therapeutic procedure, a first step in the device development process is to investigate fluid velocity and temperature changes following device deployment., Methods: A laser-heated SMP foam device was deployed in a simplified in vitro vascular model. Magnetic resonance imaging (MRI) techniques were used to assess the fluid dynamics and thermal changes associated with device deployment., Results: Spatial maps of the steady-state fluid velocity and temperature change inside and outside the laser-heated SMP foam device were acquired., Conclusions: Though non-physiological conditions were used in this initial study, the utility of MRI in the development of a thermally-activated SMP foam device has been demonstrated.
- Published
- 2009
- Full Text
- View/download PDF
28. Hierarchical dynamics of As2P2S8 quasi-molecular units in a supercooled liquid in the As-P-S system: a 31P NMR spectroscopic study.
- Author
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Gjersing EL, Sen S, Maekawa H, and Aitken BG
- Abstract
The dynamics of As2P2S8 quasi-molecular units caged in an As-S network in the supercooled chalcogenide liquid of composition (As2S3)90(P2S5)10 have been studied near the glass transition region (Tg=468
- Published
- 2009
- Full Text
- View/download PDF
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