Biodegradable plastics are currently being developed as a short-term solution to the problem of conventional plastics which persist in the soil. Little is known regarding the decomposition of the new plastics including products formed and microbial populations responsible.Polyethylene-based plastic films interspersed with 0, 5, 10 or 15% (w/w) starch were incubated for up to 112 days in laboratory and filed soils, a forced-air compost pile, and a simulated sanitary landfill. Biologically-mediated polymer decomposition was monitored via measurement of microbial respiration, release of soluble organic carbon ()C) and anions, total microbial counts, and scanning electron microscopic (SEM) observations. Microbial respiration was greatest in all treatments within the first 14 days coincided with greatest soluble OC and acid production.The 15% starch samples decomposed most rapidly in the field soils (2.57. decrease in mass over 11 days) due to the influence of sunlight and temperature extremes. Decomposition was lowest (0.1%) in the anaerobic landfill.Actinomycetes and bacteria predominated in most environments while fungi growth was inhibited in the landfill and compost. The SEM observations revealed a preferential attack of starch granules by microbes followed by a more gradual weathering of polyethylene sheets. / Department of Natural Resources

Lam Hiu Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Chinese Abstract --- p.ii / Acknowledgement --- p.iii / Table of Content --- p.vi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Differential refractometry --- p.1 / Chapter 1.2 --- Nature of refractive index --- p.2 / Chapter 1.2.1 --- Concentration dependence of refractive index --- p.3 / Chapter 1.2.2 --- Wavelength dependence of refractive index --- p.4 / Chapter 1.2.3 --- Temperature and pressure dependence of refractive index / Chapter 1.3 --- Types of differential refractometer --- p.6 / Chapter 1.3.1 --- Deflection type / Chapter 1.3.2 --- Fresnel type --- p.7 / Chapter 1.3.3 --- Interferometric type --- p.8 / Chapter 1.4 --- Reference --- p.9 / Chapter Chapter 2 --- A new laser differential refractomter for real-time measurement of refractive index variation / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Experiment / Chapter 2.2.1 --- Experimental setup --- p.14 / Chapter 2.2.2 --- Light source / Chapter 2.2.3 --- Thermostatic cuvutte --- p.16 / Chapter 2.2.4 --- Thermoelectric module --- p.18 / Chapter 2.2.5 --- Inlet and outlet --- p.20 / Chapter 2.2.6 --- Position sensitive detector --- p.21 / Chapter 2.3 --- Basic principles of differential refractometer --- p.23 / Chapter 2.4 --- Materials --- p.25 / Chapter 2.5 --- Results and discussion --- p.25 / Chapter 2.5.1 --- Instrument calibration / Chapter 2.5.2 --- Dynamic range of instrument --- p.26 / Chapter 2.5.3 --- "Instrument stability, noise and resolution" --- p.28 / Chapter 2.5.4 --- Specific refractive index increment measurement --- p.31 / Chapter 2.5.5 --- Temperature effect of refractive index increment --- p.35 / Chapter 2.5.6 --- Wavelength effect of refractive index increment / Chapter 2.6 --- Conclusion --- p.36 / Chapter 2.7 --- Reference --- p.37 / Chapter Chapter 3 --- Enzymatic degradation studies of poly(ethylene oxide)- b-poly(ε-caprolactone) copolymer nanoparticles by differential refractometer / Chapter 3.1 --- Abstract / Introduction --- p.38 / Chapter 3.2 --- Experimental --- p.39 / Chapter 3.2.1 --- Material and sample preparation --- p.41 / Chapter 3.2.2 --- Differential refractometer / Chapter 3.2.3 --- Laser light scattering --- p.41 / Results and dicussion --- p.42 / Chapter 3.3 --- Conclusion --- p.43 / Chapter 3.4 --- Acknowledgement --- p.47 / Chapter 3.5 --- References and notes --- p.48 / Chapter 3.6 / Chapter 3.6.1 --- Figures captions --- p.50 / Chapter 3.6.2 --- Table and Figures --- p.55 / Chapter Chapter 4 --- Appendix - Fundamentals of light scattering and instrumentation --- p.56 / Chapter 4.1 --- Static laser light scattering --- p.57 / Chapter 4.2 --- Dynamic light scattering --- p.58 / Chapter 4.3 --- Correlation function profile analysis --- p.60 / Chapter 4.4 --- Molar mass distribution and conformation of polymers --- p.62 / Chapter 4.5 --- Instrumentation --- p.63 / Chapter 4.6 --- Reference --- p.66

by Jim Tsz Fung. / Thesis submitted in 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Abstract also in Chinese. / Abstract --- p.i / Abstract(Chinese) --- p.iii / Acknowledgment --- p.iv / Contents --- p.v / Abbreviations --- p.vii / List of Figures --- p.xi / List of Tables --- p.xvi / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Theoretical background and instrumentation --- p.8 / Chapter 2.1 --- Static laser light scattering --- p.9 / Chapter 2.2 --- Dynamic laser light scattering --- p.10 / Chapter 2.3 --- Laser light scattering instrumentation --- p.11 / Chapter 2.4 --- Refractive index increment measurement --- p.13 / Chapter 2.5 --- The principle of steady-state fluorescence spectroscopy --- p.14 / Chapter 2.5.1 --- Solvent effects on fluorescence emission --- p.17 / Chapter 2.5.2 --- Excimer --- p.17 / Chapter 2.5.3 --- Characterization of fluorescence emission spectra of pyrene --- p.18 / Chapter 2.6 --- Polymer micronization --- p.20 / Chapter 2.7 --- Enzyme purification --- p.22 / Chapter 3. --- Laser light-scattering study of enzymatic biodegradation of poly(ε-caprolactone) --- p.25 / Chapter 3.1 --- A novel laser light scattering study of enzymatic biodegradation of PCL nanoparticles --- p.26 / Chapter 3.2 --- A modified heterogeneous kinetics for the enzymatic biodegradation of poly(s-caprolactone) in aqueous solution --- p.42 / Chapter 4. --- Laser light-scattering study of enzymatic biodegradation of poly(ethylene oxide-b-ε-caprolactone) diblock copolymer --- p.59 / Chapter 4.1 --- Enzymatic biodegradation of poly(ethylene oxide-b-ε- caprolactone) diblock copolymer and its potential biomedical applications --- p.60 / Chapter A1. --- Static laser light scattering --- p.80 / Chapter A2. --- Dynamic laser light scattering --- p.85

Lignin is the second most abundant biopolymer on Earth. It is an amorphous, cross-linked, aromatic polymer composed of phenylpropanoid units. There has been an ever growing interest in the biodegradation of this complex polymer for the last 30 years. White-rot fungi have been found to be an important lignin degraders in the natural environment. With the discovery of two groups of hemoprotein enzymes, lignin peroxidases and manganese(II)-dependent peroxidases, from the lignin degrading culture of a white-rot fungus, Phanerochaete chrysosporium, rapid progress has been made in understanding the mechanism of lignin biodegradation. Synthetic metaUoporphyrins, the iron(III) and manganese(III) complexes of meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrin (TDCSPPFeCl and TDCSPPMnCl) and meso-tetra(2,6-dichloro-3-sulfonatophenyl)-B-octachloroporphyrin (Cl₁₆TSPPFeCl and Cl₁₆TSPPMnCl), were used in this study to mimic the functions of the "lignin degrading" enzymes. Factors affecting the catalytic activities of these biomimetic catalysts were studied. TDCSPPFeCl could closely mimic lignin peroxidase in the degradation of a number of lignin model compounds, including veratryl alcohol, B-l, B-O-4, B-5, 5-5' biphenyl, phenylpropane, and phenylpropene model compounds. The reactions catalyzed by TDCSPPFeCl include benzyl alcohol oxidation, C[formula omitted],-C[formula omitted] side chain cleavage, demethoxylation, aromatic ring cleavage, benzylic methylene hydroxylation, and C[formula omitted]-C[formula omitted] double bond hydroxylation (glycol formation). Novel solvent incorporated compounds isolated from the oxidation of veratryl alcohol give insights about the site of attack of substrate cation radical by solvent molecules. The isolation of a solvent incorporated product from the oxidation of a phenylpropene model compound suggests a cation radical mechanism for the oxidation of this lignin substructure. The formation of a number of direct aromatic ring cleavage products during the oxidation of some model compounds supports the previously proposed mechanism of aromatic ring cleavage. TDCSPPFeCl was also able to catalyze the oxidation of environmental pollutants such as pyrene and 2,4,6-trichlorophenol. Veratryl alcohol and manganese(II)-complexes have been suggested to function as redox mediators for lignin biodegradation. Evidence has been provided to demonstrate their mediating power during electrochemical and biomimetic degradation of lignin model compounds. In addition to the mechanistic information obtained, the successful oxidation of the model compounds suggests that metalloporphyrins can be important catalysts for the pulp and paper industry and for pollution control. / Science, Faculty of / Chemistry, Department of / Graduate

This dissertation focuses on the development of biomaterials that could be used to enhance the regeneration of severed peripheral nerves. These materials were designed to be electroactive, biodegradable, and biocompatible. To render the materials electroactive the author chose to incorporate conducting polymer (CP) units into the materials. Because CPs are inherently non-degradable, the key challenge was to create a CP-based material that was also biodegradable. Two strategies were explored to generate a biodegradable CP-based material. The first strategy centered around the incorporation of both electroactive and biodegradable subunits into a copolymer system. In the context of this approach, two bis(methoxyquaterthiophene)-co-adipic acid polyester (QAPE) analogues were successfully synthesized, one through polycondensation (giving undoped QAPE) and the second through oxidative polymerization (giving doped QAPE-2). QAPE was found to be electroactive by cyclic voltammetry, bioerodible, and cytocompatible with Schwann cells. QAPE was doped with ferric perchlorate, although only a low doping percentage was realized (~8%). Oxidative polymerization of a bis(bithiophene) adipate permitted the direct synthesis of doped QAPE-2, which was found to have a higher doping level (~24%). The second strategy pursued with the goal of generating an electroactive biodegradable material involved covalently immobilizing low molecular weight polythiophene chains onto the surface of crosslinked hyaluronic acid (HA) films. HA films are not only biodegradable and biocompatible, but they also provide mechanical integrity to bilayer systems. Dicyclocarbodiimide coupling of carboxylic acids to HA alcohol groups was used to functionalize HA films. The HA-polythiophene composite is still in the early stages of development. However, to date, thiophene has been successfully immobilized at the surface of HA films with a high degree of substitution. The author has also shown that thiophene polymerization can be achieved at the surface of these functionalized films and that the extent of polymer immobilization appears to be affected by the presence of immobilized thiophene. The results reported in this dissertation lead the author to suggest that it is possible to generate biodegradable electroactive materials. Further, she believes that with additional optimization these materials may prove beneficial for the regeneration of peripheral nerves and possibly other tissues that respond favorably to electrical stimulation. / text

No description available.

Includes bibliographical references (leaves G-1-G-11 ). / vii, 1 v. (various pagings) : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Substatial developmental work is required to acheive economically attractive poly-hydroxyalkanoate (PHA) production. Aims to improve the understanding of PHA production by recombinant Escherichia coli, with a view to guiding future developmental work. Also suggests numerous areas where further improvements to PHB production are possible, and proposes ways in which they could be implemented. / Thesis (Ph.D.)--Adelaide University, Dept. of Chemical Engineering, 2001

No description available.

M.Sc. (Chemistry) / Please refer to full text to view abstract.

Orientador: Nelson Eduardo Duran Caballero / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T19:54:09Z (GMT). No. of bitstreams: 1 Gaspari_PriscylaDanielyMarcato_M.pdf: 3916509 bytes, checksum: 15b4d148bf7fb5ebc6d8b40b2108c914 (MD5) Previous issue date: 2006 / Resumo: O projeto consistiu na preparação e caracterização de sistemas de liberação sustentada veiculando a estreptomicina, um agente antimicobacteriano. A estreptomicina (STM) foi encapsulada em micropartículas poliméricas preparadas a partir do polímero biodegradável poli(e-caprolactona) (PCL) e do copolímero biodegradável poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBV), pela técnica de emulsificação seguida da evaporação do solvente. Estas partículas foram caracterizadas quanto ao diâmetro médio e distribuição de tamanho, morfologia, Potencial Zeta e eficiência de encapsulamento. Micropartículas de PCL e PHBV foram obtidas pelo método de dupla emulsão e evaporação de solvente com diferentes morfologias, sendo que as partículas de PCL apresentaram superfície mais lisa do que as de PHBV. Além disto, a adição do co-solvente acetona na fase orgânica, provocou a formação de micropartículas de PHBV maiores e mais porosas. Alterações em parâmetros da preparação como, aumento da concentração do tensoativo, evaporação de solvente a baixa pressão e uso de polímero com menor massa molar foram fatores que reduziram do diâmetro das partículas. A eficiência de encapsulamento nas micropartículas de PHBV, medida por eletroforese capilar, foi de 43 ± 4 %. No ensaio biológico in vitro em células V- 79 (células de fibroblastos de pulmão derivadas de hamsters chineses), hepatócitos e Vero (células do rim de macaco) foi verificada baixa toxicidade do antibiótico estreptomicina nos alvos celulares avaliados (captura do corante vermelho neutro, conteúdo de ácidos nucléicos e redução do corante metiltiazoletetrazolium). Entretanto, as micropartículas de PHBV com e sem fármaco apresentaram alteração no lisossoma, que pode ter sido causada pela presença de PVA na superfície das partículas. A atividade antimicrobiana da estreptomicina livre e encapsulada frente à Escherichia coli foi verificada, obtendo menor eficiência do fármaco encapsulado em relação ao fármaco livre. Entretanto, nos testes frente à Streptococcus lentus, foi verificada maior eficiência quando o fármaco estava encapsulado. / Abstract: This research was related to the preparation and characterization of a sustained release system with streptomycin, an antimycobacterial agent. The streptomycin (STM) was encapsulated in polymeric micro and nanopartículas from the biodegradable polymers, poli(e-caprolactona) (PCL) and of the biodegradable copolymers, poli(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV), by double emulsion and solvent evaporation method. These particles were characterized in function of the size and size distribution, morphology, Potential Zeta and encapsulation efficiency. PCL and PHBV microparticles that were obtained by described methods, PCL presented surface smoother than the PHBV microparticles. Moreover, the addiction of the co-solvent acetone in the organic phase provoked the formation of PHBV microparticles larger and more porous than in PCL. Alterations in preparation parameters such as increase of the surfactant concentration, solvent evaporation in low pressure and a decrease molar mass were factors that reduced the particle sizes. The encapsulation efficiency in microparticles of PHBV, measured by capillary electrophoresis, it was 43 ± 4.4%. In the in vitro biological assay in V-79 cells (permanent lung fibroblasts cell line derived from Chinese hamsters), hepatocytes and Vero cells (from monkey kidney) was verified low toxicity of the streptomycin in the endpoints targets (neutral red uptake, nucleic acid content and tetrazolium reduction). However, microparticles of PHBV with and without drug demonstrated an alteration in the lysosome that it could have been caused by the presence of poly vinylic alcohol (PVA) in the particles surfaces. The antimicrobial activity of free and encapsulated streptomycin against Escherichia coli was demonstrated. A smaller efficiency of encapsulated drug than the free one was found. However, in the tests against Streptococcus lentus was verified larger efficiency of the free drug than the encapsulated one. / Mestrado / Físico-Química / Mestre em Química