Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1908. / The entire thesis text is included in file. Typescript. Illustrated by authors. Title from title screen of thesis/dissertation PDF file (viewed November 24, 2008)

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 184-187).

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1905. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed November 18, 2008)

Thesis (M.S.M.E.)--State University of New York at Binghamton, Watson School of Engineering and Applied Science, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 98-103). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 98-103). Also available on the Internet.

Thesis (M.S.)--State University of New York at Binghamton, Program of Materials Science and Engineering, 2007. / Includes bibliographical references.

The development of novel bio-based materials with antimicrobial properties for active packaging applications is a topic of significant interest. The current PhD thesis deals with the development of biotechnologically derived polyhydroxyalkanoates (PHAs) based on nanometals for antimicrobial active food packaging applications. Initially, silver nanoparticles (AgNPs) were produced by chemical reduction and stabilized in situ within unpurified poly(hydroxybutyrate-co-hydroxyvalerate), PHBV18 (18 mol% valerate) suspensions previously obtained from mixed microbial cultures. The stabilized AgNPs were subsequently used to develop PHAs-AgNPs nanocomposites following two different strategies: 1) a direct melt-blending process where the AgNPs were added to the PHBV3 (3% mol valerate) from a highly dispersed and distributed enriched masterbatch form and, 2) as an annealed electrospun coating of PHBV3/PHBV18/AgNPs over compression molded PHBV3. The implementation of both strategies resulted in active nanocomposites with strong antimicrobial activity against food-borne pathogens, being the electrospinning coating technique the most efficient one in reducing the bacterial and virus population, even at very low AgNPs loading (from 0.002 to 0.04% wt.). As an alternative route, an integrated bioprocess for the biological synthesis of AgNPs and polyhydroxybutyrate (PHB) from the fermentation process with Cupriavidus necator was also carried out. Interestingly, this work demonstrated for the first time, the inherent capacity of C. necator to reduce silver nitrate and produce AgNPs without the need for adding a reducing agent. The process was successfully optimized and scaled-up to a fully automated 10 liters bioreactor. Finally, because of the limitations of the use of AgNPs in food applications, antimicrobial PHAs films based on zinc oxide (ZnO) and copper oxide (CuO) nanoparticles were prepared according to the previously developed strategies but in this case, a melt-mixing process of preincorporated ZnO into unpurified PHBV18 fiber mats made by electrospinning was also carried out to stabilize the metal nanoparticles. The effect of ZnO nanoparticles morphology and the method of ZnO/CuO incorporation on the morphological, optical, thermal, mechanical and barrier properties of the resulting active films as well as their influence on the antimicrobial (bactericide and virucidal) performance were studied. Thus, this PhD thesis represents a significant step forward in the understanding of the antimicrobial efficacy of highly dispersed and distributed nanometals and highlights the suitability of the developed PHAs/nanometals materials for antimicrobial applications and in particular for antimicrobial active food packaging applications. / El desarrollo de nuevos biomateriales con propiedades antimicrobianas para aplicaciones de envasado activo resulta un tema de gran interés en la actualidad. La presente tesis doctoral estudia el desarrollo por vía biotecnológica de polihidroxialcanoatos (PHAs) conteniendo nanometales para aplicaciones de envasado activo antimicrobiano de alimentos. En primer lugar, se produjeron nanopartículas de plata (AgNPs) por reducción química y se estabilizaron in situ en una suspensión de poli (hidroxibutirato-co-hidroxivalerato) no purificado, PHBV18 (18% en moles de valerato), obtenido previamente a partir de cultivos mixtos microbianos. Posteriormente, las AgNPs estabilizadas se utilizaron para desarrollar nanocompuestos de PHAs-AgNPs siguiendo dos estrategias diferentes: 1) un proceso de mezclado-fundido en donde las AgNPs se añadieron al PHBV3 (3% mol de valerato) a partir de un masterbatch de nanopartículas altamente dispersas y distribuidas y, 2) como una estructura bicapa formada por un recubrimiento a base de PHBV/PHBV18/AgNPs depositado sobre un film de PHBV3 obtenido por moldeo por compresión. La aplicación de ambas estrategias dio lugar a nanocompuestos activos con una fuerte actividad antimicrobiana frente a patógenos transmitidos por los alimentos, siendo la estructura bicapa la más eficaz en la reducción de la población bacteriana y viral, incluso a una carga muy baja de AgNPs (de 0.002 a 0.04% en peso). Como ruta alternativa, también se llevó a cabo un proceso integrado de fermentación con Cupriavidus necator para la síntesis biológica de AgNPs y polihidroxibutirato (PHB). En este trabajo se demostró, por primera vez, la capacidad inherente de C. necator para reducir nitrato de plata y producir AgNPs sin la necesidad de añadir un agente reductor. El proceso fue optimizado y escalado satisfactoriamente a un biorreactor automatizado de 10 litros. Finalmente, debido a las limitaciones del uso de AgNPs en aplicaciones alimentarias, se prepararon films antimicrobianos de PHAs basados en nanopartículas de óxido de zinc (ZnO) y óxido de cobre (CuO) de acuerdo con las estrategias previamente desarrolladas. Adicionalmente, ambas estrategias se compararon con una tercera basada en la preincorporación de ZnO en fibras de PHBV18 no purificado y su posterior mezclado-fundido con polímero virgen. Se estudió el efecto de la morfología de las nanopartículas de ZnO y del método de incorporación de ZnO/CuO sobre las propiedades morfológicas, ópticas, térmicas, mecánicas y de barrera de los films activos resultantes, así como su influencia en el comportamiento antimicrobiano (bactericida y virucida). Por lo tanto, esta tesis doctoral representa un avance significativo en la comprensión de la eficacia antimicrobiana de nanometales altamente dispersos y distribuidos y destaca la idoneidad de los materiales desarrollados a base de PHAs y nanometales para aplicaciones antimicrobianas y, en particular, para aplicaciones de envasado de alimentos activos antimicrobianos. / El desenvolupament de nous materials d'origen biològic amb propietats antimicrobianes per a aplicacions d'envasament actiu és un tema d'interès significatiu. La tesi doctoral actual s'ocupa del desenvolupament de polihidroxialcanoats (PHA) reforçats amb nanometals per via biotecnològicament per a aplicacions d'envasat actiu antimicrobià d'aliments. Inicialment, les nanopartícules de plata (AgNPs) van ser produïdes per reducció química i estabilitzades in situ dins en suspensions de poli (hidroxibutirato-co-hidroxivalerato) sense purificar, PHBV18 (18 mol% de valerat), prèviament obtinguts a partir de cultius mixtes microbians. Las AgNPs estabilitzades es van usar posteriorment per a desenvolupar nanocompostos de PHA's- AgNPs seguint dues estratègies diferents: 1) Procés directe de barreja en fusió que no utilitza dissolvents orgànics o estabilitzants addicionals i on es van afegir les AgNPs al PHBV3 (3% mol valerato) a partir d¿un masterbath on estaven perfectament disperses i distribuïdes 2) com una estructura bicapa formada per un recobriment de PHBV3 / PHBV18/AgNPS que es deposita sobre un film de PHBV3 obtingut per modelat per compressió. L'aplicació d'ambdues estratègies va donar lloc a nanocompostos actius amb una forta activitat antibacteriana enfront de patògens transmesos pels aliments, sent l'estructura de doble capa la més eficaç en la reducció de la població bacteriana i viral, fins i tot a una càrrega molt baixa de AgNPs (de 0.002-0.04% en pes). Com ruta alternativa, també es va dur a terme un procés integrat de fermentació amb Cupriavidus necator per a la síntesi biològica de AgNPs i polihidroxibutirato (PHB). En aquest treball es demostra, per primera vegada, la capacitat inherent de C. necator per reduir la sal de plata i produir AgNPs sense la necessitat d'afegir un agent reductor. El procés va ser optimitzat i escalat satisfactòriament a un bioreactor de 10 litres. Finalment, a causa de les limitacions de l'ús de nanopartícules de plata en aplicacions alimentàries, es van preparar films antimicrobians de PHA que incorporessin nanopartícules d'òxid de zinc (ZnO) i òxid de coure (CuO) d'acord amb les estratègies prèviament desenvolupades. Les dues estratègies es van comparar amb una tercera basada en la preincorporació de ZnO en fibres de PHBV18 no purificat i aquestes fibres es van barrejar posteriorment amb polímer verge. Es va estudiar l'efecte de la morfologia de les nanopartícules de ZnO i el mètode de la incorporació de ZnO/CuO sobre les propietats morfològiques, òptiques, tèrmiques, mecàniques i de barrera dels films actius resultants, així com la seva influència en el comportament antimicrobià (bactericida i virucida). Per tant, aquesta tesi doctoral representa un pas endavant significatiu en la comprensió de l'eficàcia antimicrobiana de nanometales altament dispersos i distribuïts i posa en relleu la idoneïtat dels materials desenvolupats basats en PHAs i nanometals per a aplicacions antimicrobianes i, en particular, per a aplicacions d'envasat d'aliments actius antimicrobians. / Castro Mayorga, JL. (2017). Biotechnological routes for the development of antimicrobial nano-metal based polyhydroxyalkanoates for active food packaging applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/85678 / TESIS

Ion exchange of heavy metals with zeolites is important in terms of different application areas. Industrial wastewater treatment and antibacterial applications are two essential areas that have taken great attention. While silver, zinc and copper are well known for their toxicity, they are also used as antibacterial agents in zeolites. The objective of this study is to investigate the single and multicomponent ion exchange behavior of zeolite 4A for silver, zinc, copper and sodium ions. For this purpose Ag+-Na+, Zn2+-Na+, Cu2+-Na+ binary systems and Ag+-Zn2+-Na+, Ag+-Cu2+-Na+, Cu2+-Zn2+-Na+ ternary systems were investigated in batch systems at 25&deg / C and 0.1 N. Binary ion exchange isotherms indicate that zeolite 4A has high selectivity for silver, zinc and copper with respect to sodium. All exchange isotherms lie above the diagonal over the whole range. Using the equilibrium data, the thermodynamic analysis of the binary systems were carried out. The thermodynamic equilibrium constants and the standard free energies of exchange were calculated as 340.9 and -14.5 kJ/mol for silver-sodium system, 40.5 and -4.6 kJ/mol for zinc-sodium system, and 161.2 and -6.3 kJ/mol for copper-sodium system, respectively. From these values, selectivity sequence of zeolite 4A was determined as Ag+ &gt / Cu2+ &gt / Zn2+. This selectivity sequence was also verified by the results of ternary ion exchange experiments. The experimental data were compared with the Langmuir and Freundlich isotherms. While Freundlich model gives a better correlation for Ag+-Na+ and Zn2+-Na+ exchange, Langmuir model represents a better fit to the experimental data of Cu2+-Na+ exchange.

This work computationally investigates the partial oxidation of ethylene (i.e. ethylene epoxidation) using periodic Density Functional Theory (DFT) on slab models that represent the catalyst surfaces. The mechanical aspects of the reaction were investigated on silver surfaces, which are industrially applied catalysts, for a wide range of surface models varying from metallic surfaces with low oxygen coverage to oxide surfaces. For comparison, the metallic and oxide phases of copper and gold were also studied. On these surfaces, the reaction paths and the transition states along these paths for the selective and non-selective reaction channels were obtained using the climbing image nudged elastic band (CI-NEB) method. In order to answer the question &ldquo / what is the relation between the surface state and the ethylene oxide selectivity?&rdquo / metallic (100), (110) and (111) surfaces of Cu, Ag and Au / and, (001) surfaces of Cu2O, Ag2O and Au2O oxides were studied and compared. For the studied metallic surfaces, it was found that the selective and non-selective reaction channels proceed through the oxametallacycle (OMC) intermediate, and the product selectivity depends on the relative barriers of the these channels, in agreement with the previous reports. However for the studied metallic surfaces and oxygen coverages, a surface state that favors the ethylene oxide (EO) formation was not identified. The studied Au surfaces did not favor the oxygen adsorption and dissociation, and the Cu surfaces favored the non-selective product (acetaldehyde, AA) formation. Nevertheless, the results of Ag surfaces are in agreement with the ~50% EO selectivity of the un-promoted silver catalyst. The catalyst surface in the oxide state was modeled by the (001) surfaces of the well defined Cu2O, Ag2O and Au2O oxide phases. Among these three oxides, the Cu2O is found not to favor EO formation whereas Au2O is known to be unstable, however selective for epoxidation. The major finding of this work is the identification of a direct epoxidation path that is enabled by the reaction of the surface oxygen atoms, which are in two-fold (i.e. bridge) positions and naturally exist on (001) oxide surfaces of the studied metals. Among the three oxides studied, only Ag2O(001) surface does not show a barrier for the formation of adsorbed epoxide along the direct epoxidation path. Moreover, the overall heat of reaction that is around 105 kJ/mol agrees well with the previous reports. The single step, direct epoxidation path is a key step in explaining the high EO selectivities observed. Also for the oxide surfaces, the un-selective reaction that ends up in combustion products is found to proceed through the OMC mechanism where aldehyde formation is favored. Another major finding of this study is that, for the studied oxide surfaces two different types of OMC intermediates are possible. The first possibility is the formation of the OMC intermediate on oxygen vacant sites, where the ethylene can interact with the surface metal atoms directly. The second possibility is the formation of a direct OMC intermediate, through the interaction of the gas phase ethylene with the non-vacant oxide surface. This occurs through the local surface reconstruction induced by the ethylene. The effect of Cl promotion was also studied. Coadsorption of Cl is found to suppress the oxygen vacant sites and also the reconstruction effects that are induced by ethylene adsorption. Thus, by preventing the interaction of the ethylene directly with the surface metal atoms, Cl prevents the OMC formation, therefore the non-selective channel. At the same time Cl increases the electrophilicity of reacting surface oxygen. The direct epoxidation path appears to be stabilized by coadsorbed oxygen atoms. Thus, we carry the discussions on the silver catalyzed ethylene epoxidation one step further. Herein we present that the EO selectivity will be limited in the case of metallic catalyst, whereas, the oxide surfaces enable a direct mechanism where EO is produced selectively. The role of the Cl promoter is found to be mainly steric where it blocks the sites of non-selective channel.