910 research outputs found

    Computational and experimental studies on the reaction mechanism of bio-oil components with additives for increased stability and fuel quality

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    As one of the world’s largest palm oil producers, Malaysia encountered a major disposal problem as vast amount of oil palm biomass wastes are produced. To overcome this problem, these biomass wastes can be liquefied into biofuel with fast pyrolysis technology. However, further upgradation of fast pyrolysis bio-oil via direct solvent addition was required to overcome it’s undesirable attributes. In addition, the high production cost of biofuels often hinders its commercialisation. Thus, the designed solvent-oil blend needs to achieve both fuel functionality and economic targets to be competitive with the conventional diesel fuel. In this thesis, a multi-stage computer-aided molecular design (CAMD) framework was employed for bio-oil solvent design. In the design problem, molecular signature descriptors were applied to accommodate different classes of property prediction models. However, the complexity of the CAMD problem increases as the height of signature increases due to the combinatorial nature of higher order signature. Thus, a consistency rule was developed reduce the size of the CAMD problem. The CAMD problem was then further extended to address the economic aspects via fuzzy multi-objective optimisation approach. Next, a rough-set based machine learning (RSML) model has been proposed to correlate the feedstock characterisation and pyrolysis condition with the pyrolysis bio-oil properties by generating decision rules. The generated decision rules were analysed from a scientific standpoint to identify the underlying patterns, while ensuring the rules were logical. The decision rules generated can be used to select optimal feedstock composition and pyrolysis condition to produce pyrolysis bio-oil of targeted fuel properties. Next, the results obtained from the computational approaches were verified through experimental study. The generated pyrolysis bio-oils were blended with the identified solvents at various mixing ratio. In addition, emulsification of the solvent-oil blend in diesel was also conducted with the help of surfactants. Lastly, potential extensions and prospective work for this study have been discuss in the later part of this thesis. To conclude, this thesis presented the combination of computational and experimental approaches in upgrading the fuel properties of pyrolysis bio-oil. As a result, high quality biofuel can be generated as a cleaner burning replacement for conventional diesel fuel

    Effects of municipal smoke-free ordinances on secondhand smoke exposure in the Republic of Korea

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    ObjectiveTo reduce premature deaths due to secondhand smoke (SHS) exposure among non-smokers, the Republic of Korea (ROK) adopted changes to the National Health Promotion Act, which allowed local governments to enact municipal ordinances to strengthen their authority to designate smoke-free areas and levy penalty fines. In this study, we examined national trends in SHS exposure after the introduction of these municipal ordinances at the city level in 2010.MethodsWe used interrupted time series analysis to assess whether the trends of SHS exposure in the workplace and at home, and the primary cigarette smoking rate changed following the policy adjustment in the national legislation in ROK. Population-standardized data for selected variables were retrieved from a nationally representative survey dataset and used to study the policy action’s effectiveness.ResultsFollowing the change in the legislation, SHS exposure in the workplace reversed course from an increasing (18% per year) trend prior to the introduction of these smoke-free ordinances to a decreasing (−10% per year) trend after adoption and enforcement of these laws (β2 = 0.18, p-value = 0.07; β3 = −0.10, p-value = 0.02). SHS exposure at home (β2 = 0.10, p-value = 0.09; β3 = −0.03, p-value = 0.14) and the primary cigarette smoking rate (β2 = 0.03, p-value = 0.10; β3 = 0.008, p-value = 0.15) showed no significant changes in the sampled period. Although analyses stratified by sex showed that the allowance of municipal ordinances resulted in reduced SHS exposure in the workplace for both males and females, they did not affect the primary cigarette smoking rate as much, especially among females.ConclusionStrengthening the role of local governments by giving them the authority to enact and enforce penalties on SHS exposure violation helped ROK to reduce SHS exposure in the workplace. However, smoking behaviors and related activities seemed to shift to less restrictive areas such as on the streets and in apartment hallways, negating some of the effects due to these ordinances. Future studies should investigate how smoke-free policies beyond public places can further reduce the SHS exposure in ROK

    Structural basis of bacterial glyeans biosynthesis and processing: ímpact in human health and disease

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    181 p.El objetivo a largo plazo de nuestro grupo es estudiar a nivel molecular la estructura, la especificidad por sustrato y el mecanismo de acción de diferentes enzimas bacterianas involucradas en el reconocimiento o modificación de carbohidratos que sean relevantes en la interacción, tanto beneficiosa como patogénica, con el ser humano como hospedador.En este contexto, durante mi tesis, he trabajado en la comprensión a nivel estructural de la catálisis, así como del mecanismo de reconocimiento del sustrato de enzimas de bacterias tanto beneficiosas (Akkermansia muciniphila) como perjudiciales (Mycobacterium tuberculosis) para la salud del hospedador. Siguiendo este criterio, la tesis ha sido dividida en dos secciones; el estudio de la maquinaria enzimática que Akkermansia muciniphila, bacteria que forman parte de la microbiota intestinal, presenta para la digestión de los azúcares presentes en las mucinas por un lado, y el estudio de la biosíntesis de los glucolípidos (fosfatidil-myo-inositol mannósidos; PIMs, lipomannanos; LM y lipoarabinomannanos; LAM) presentes en la compleja envoltura celular de M. tuberculosis, por otro lado

    Development of spectroscopic assays for rapid monitoring of estrogen biodegradation

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    Estrogen hormones are well-established environmental micropollutants which have been linked to endocrine disruption in aquatic organisms in wastewater discharge sites. Biological degradation is the primary wastewater treatment mechanism for estrogen removal. However, treatment efficacy is highly variable and difficult to engineer due to the “black box” nature of biological treatment. Microbial strain selection is a critical impediment towards engineering estrogen biodegradation, since isolating endogenous strains with specific metabolic traits requires lengthy enrichment cultures and is limited to culturable organisms. Furthermore, the highly sensitive and selective chemical trace analysis techniques used to measure estrogen removal are relatively expensive and inefficient. In this thesis, we developed rapid, high-throughput spectroscopic methods designed to monitor estrogen biodegradation. The spectroscopic methods include a fluorometric assay based on the uptake of a fluorescently-labelled estrogen and a colorimetric biosensor using gold nanoparticles (AuNPs) and an aptamer bioreceptor. A synthetic microbial community comprised of characterised estrogen-degrading reference strains was used to evaluate the fitness for purpose of the developed methods. A trace analysis method using conventional chromatography was developed to validate the use of the fluorescent probes with the synthetic microbial community. The biochemical fate and distribution of the BODIPY-estrogen in the estrogen-degrading bacteria – specifically, the biotransformation of BODIPY-estradiol to BODIPY-estrone by Caenibius tardaugens – was used to inform the design of the fluorometric assay. The fluorometric assay utilises a cell impermeable halide quencher to suppress the extracellular fluorescence, and thus, the obtained fluorescence response was attributed to the selective internalisation of BODIPY-estrogen by C. tardaugens. While the fluorometric assay was developed to screen for estrogen-degrading bacteria, the colorimetric aptasensor, which was adapted from published AuNP biosensors and aptamers for this application, was developed to quantify 17β-estradiol (E2) in buffered culture media. The developed aptasensor was evaluated against industry guidelines for ligand-binding assays. While the analytical performance of the aptasensor satisfied the majority of the guidelines’ acceptance criteria, the method suffered from biological interferences by the estrogen-degrading bacteria. The work in this thesis contributes towards expanding the available bioanalytical methods in environmental biotechnology

    Modern meat: the next generation of meat from cells

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    Modern Meat is the first textbook on cultivated meat, with contributions from over 100 experts within the cultivated meat community. The Sections of Modern Meat comprise 5 broad categories of cultivated meat: Context, Impact, Science, Society, and World. The 19 chapters of Modern Meat, spread across these 5 sections, provide detailed entries on cultivated meat. They extensively tour a range of topics including the impact of cultivated meat on humans and animals, the bioprocess of cultivated meat production, how cultivated meat may become a food option in Space and on Mars, and how cultivated meat may impact the economy, culture, and tradition of Asia

    Navigating chemical reaction space with a steering wheel

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    Autonomous reaction network exploration algorithms offer a systematic approach to explore mechanisms of complex chemical processes. However, the resulting reaction networks are so vast that an exploration of all potentially accessible intermediates is computationally too demanding. This renders brute-force explorations unfeasible, while explorations with completely pre-defined intermediates or hard-wired chemical constraints, such as element-specific coordination numbers, are not flexible enough for complex chemical systems. Here, we introduce a Steering Wheel to guide an otherwise unbiased automated exploration. The Steering Wheel algorithm is intuitive, generally applicable, and enables one to focus on specific regions of an emerging network. It also allows for guiding automated data generation in the context of mechanism exploration, catalyst design, and other chemical optimization challenges. The algorithm is demonstrated for reaction mechanism elucidation of transition metal catalysts. We highlight how to explore catalytic cycles in a systematic and reproducible way. The exploration objectives are fully adjustable, allowing one to harness the Steering Wheel for both structure-specific (accurate) calculations as well as for broad high-throughput screening of possible reaction intermediates.Comment: 40 pages, 10 figures, 1 tabl

    Towards light-driven catalysis in block copolymer micelles

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    Im Rahmen dieser Arbeit wurden die Synthese, Charakterisierung und Untersuchungen polymerbasierter, sogenannter „weicher“ Materie als Matrizen für lichtgetriebene Redoxreaktionen behandelt. Der erste Teil dieser Arbeit umfasste die Präparation von pH-responsiven Mizellen in Wasser auf Grundlage von maßgeschneiderten, amphiphilen Blockcopolymeren, wobei unter anderem die im hydrophilen Teil vorhandenen Liganden zur Anbindung von Übergangsmetallkomplexen genutzt wurden. Auf diese Weise konnten (photo)katalytisch aktive Zentren innerhalb der pH-sensitiven Corona der Mizellen integriert werden. Mit diesem Ansatz war es möglich, mittels Konformationsänderungen der Corona der Mizellen deren Aktivität in verschiedenen, photokatalytischen Systemen experimentell zu kontrollieren und mit theoretischen Modellen zu analysieren. Der zweite Teil dieser Abhandlung widmete sich der Verwendung eines alternativen, polaren und funktionalisierbaren Monomer zum Aufbau analoger Blockcopolymerarchitekturen in methanolischen Lösungen sowie einer Anwendung in photokatalytischen Prozessen. Es ließen sich auf der chemischen Struktur basierende Indizien einer weit über die bloße mechanische Integration hinausreichende Funktion der Matrix feststellen. Dies wurde auch durch eine gesamtheitliche Betrachtung beider Systeme herausgearbeitet. Der dritte Teil dieser Arbeit fokussierte sich auf photokatalytische Modellsysteme, um Fallstudien zur Reproduzierbarkeit in einem modularen Photoreaktor durchzuführen. Ein weiteres Modellsystem wurde für eine didaktische Anwendung zugänglich gemacht. Mit dieser Arbeit war es möglich einen substanziellen Beitrag zur weichen Materie-vermittelten lichtgetriebenen Katalyse zu leisten. Dies geschah sowohl durch die Präsentation von Konzepten zur Integration derartiger Systeme in weicher Materie als auch der resultierenden Möglichkeit stoffliche und energetische Mechanismen in solchen Matrizen nachzuvollziehen

    Rationales Design von polyfluorierten und enzymatisch abbaubaren Biomaterialien auf Peptidbasis

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    Amphiphilic peptide-based biomaterials are of great interest for pharmaceutical and biomedical applications and mainly associated with pronounced biocompatibility and biodegradability. In fact, introducing fluorine-containing amino acids into peptides & proteins offers an unique opportunity to enhance their biophysical properties such as membrane permeability. Through its influence on hydrophobicity and polarity, the degree of fluorination dictates the extent of fluorine-specific interactions on peptide folding and stability, intermolecular interactions, and biological activity. The first study of this doctoral thesis describes the folding, self-assembly, and hydrogelation of single-strand amphipathic peptides with different degrees of fluorination on the amino acid side chains by the iterative incorporation of monofluoroethylglycine (MfeGly), difluoroethylglycine (DfeGly), and trifluoroethylglycine (TfeGly). A combination of experimental and theoretical approaches proved a higher degree of side chain fluorination to promote β-sheet formation and the rheological stability of peptide-based hydrogels in physiological conditions, whereas secondary structure formation was inhibited at a low fluorine content due to fluorine-induced polarity. In a follow-up study, the selective modification of antimicrobial peptides (AMPs) by fluorinated amino acids was investigated. A β-hairpin-forming peptide motif, whose amphipathic structure enables the targeted disruption of bacterial cell membranes, was therefore examined. Extensive MIC screening with Gram-negative and Gram-positive bacteria confirmed highly fluorinated amino acids such as trifluoroethylglycine (TfeGly) or pentafluoropropylglycine (PfpGly) to strengthen the bioactivity of the AMPs through enhanced intrinsic hydrophobicity without causing a simultaneous increase in toxic & hemolytic properties. Numerous studies on the singular incorporation of fluorinated amino acids have been published to date, whereas synthetic peptides with larger or exclusive amounts of these building blocks remained unexplored. That drove the motivation for the herein-described development and characterization of so-called "fluoropeptides". In brief, β-sheet to α-helix or fluorine-induced PPII-helix transitions were observed in SDS-supplemented buffer (pH 7.4). In situ SEIRAS experiments with POPC:POPG-based membrane models functioned to investigate the fluoropeptide’s lipid insertion and (re)folding. Thus, the highest α-helical secondary structure content was found for the nonfluorinated homooligopeptide and decreased in the order of tri-, di-, and mono-fluorination of the side chains. An important focus of this doctoral thesis was the evaluation of biodegradability for especially higher polyfluorinated sequences. In fact, all peptides prepared in this work could be hydrolyzed by various proteases regardless of the fluorine content. In cooperation with the University College Dublin, first data on the microbial digestion of fluorinated peptides and individual amino acids could be generated. The enzyme-catalyzed cleavage of the C-F bond on the side chain for both kind of substrates was, for instance, proven by detection of released fluoride ions in solution. The results of this work will contribute to the rational design and potential application of polyfluorinated peptides, whose enzymatic degradability is going to be of great interest for the future development of fluorinated biomaterials.Amphiphile peptidbasierte Biomaterialien sind vom großen Interesse für pharmazeutische und biomedizinische Anwendungen und überzeugen zumeist durch ihre Biokompatibilität und Bioabbaubarkeit. Die Einführung von fluorhaltigen Aminosäuren in Peptide & Proteine bietet hierbei die einzigartige Möglichkeit, ihre biophysikalischen Eigenschaften wie etwa die Membranpermeabilität zu verstärken. Insbesondere der Fluorierungsgrad spielt eine entscheidende Rolle, da er durch seinen Einfluss auf die Hydrophobie und Polarität die Gesamtheit fluor-spezifischer Wechselwirkungen auf die Peptidfaltung und -stabilität, intermolekularen Wechselwirkungen und biologische Aktivität steuern kann. Die erste Studie dieser Doktorarbeit beschreibt die Faltung, Selbstassemblierung und Hydrogelierung von einzelsträngigen amphipathischen Peptiden mit unterschiedlichen Fluorierungsgraden der Aminosäureseitenketten durch den iterativen Einbau von Monofluorethylglycin (MfeGly), Difluorethylglycin (DfeGly) und Trifluorethylglycin (TfeGly). Mittels einer Kombination aus experimentellen und theoretischen Ansätzen konnte gezeigt werden, dass bei physiologischen Bedingungen ein höherer Fluorierungsgrad die Bildung von β-Faltblattstrukturen und die rheologische Stabilität der peptid-basierten Hydrogele fördert, jedoch diese Sekundärstruktur von Peptiden mit niedrigem Fluorgehalt durch die fluor-induzierte Polarität inhibiert wird. In einer weiteren Studie wurde die gezielte Modifizierung der biologischen Eigenschaften antimikrobieller Peptide (AMP) durch den Einbau fluorierter Aminosäuren untersucht. Hierzu wurde ein β-Hairpin bildendes Peptidmotiv ausgewählt, dessen amphipathische Struktur die zielgerichtete Disruption bakterieller Zellmembrane ermöglicht. Die ermittelten minimalen Hemmkonzentrationen (MHK) gegen verschiedene Gram-negative und Gram-positive Bakterien zeigen, dass hochfluorierte Aminosäuren wie Trifluorethylglycin (TfeGly) und Pentafluorpropylglycin (PfpGly) die Bioaktivität antimikrobieller Peptide durch Erhöhung der intrinsischen Hydrophobie selektiv verstärken können, ohne eine gleichzeitige Zunahme toxischer & hämolytischer Eigenschaften zu verursachen. Zahlreiche Studien zum singulären Einbau fluorierter Aminosäuren wurden bis dato veröffentlicht, während synthetische Peptide mit größeren bzw. ausschließlichen Mengen dieser Bausteine unerforscht blieben. Dies war die Motivation zur Entwicklung und Charakterisierung sogenannter "Fluoropeptide". In SDS-beinhaltenden Puffer (pH 7.4) wurden, unter anderem, Übergänge von β-Faltblatt Strukturen zu α-Helices oder Fluor-induzierte PPII-Helices beobachtet. In-situ SEIRAS-Studien mit POPC:POPG-basierten Membranmodellen dienten zum Studium der Lipidinsertion und (Rück-)-Faltung der Fluoropeptide in Abhängigkeit zum gesamten Fluoranteil. Hierbei wurde der höchste Gehalt an α-helikaler Sekundärstruktur für das nichtfluorierte Homooligopeptid bestimmt, welcher in der Reihenfolge der Tri-, Di- und Monofluorierung der Seitenkette abnahm. Ein wichtiger Schwerpunkt dieser Doktorarbeit war die Bewertung der biologischen Abbaubarkeit für insbesondere höher polyfluorierte Sequenzen. Tatsächlich konnten alle in dieser Arbeit hergestellten Peptide unabhängig vom Fluorgehalt durch verschiedene Proteasen hydrolysiert werden. In Zusammenarbeit mit dem University College Dublin konnten zudem erste Daten zum mikrobiellen Verdau fluorierter Peptide und Aminosäuren generiert werden. Die enzymkatalysierte Spaltung der C-F-Bindung an der Seitenkette für beide Substratarten wurde beispielsweise durch den Nachweis von freigesetzten Fluorid-Ionen in Lösung nachgewiesen. Die Ergebnisse dieser Arbeit werden zum rationalen Design und potenzieller Anwendbarkeit neuartiger polyfluorierter Peptide beitragen, deren enzymatische Abbaubarkeit von großem Interesse für die künftige Entwicklung fluorhaltiger Biomaterialien sein wird
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