<p>Rapid growth of energy consumption and greenhouse gas emissions from fossil fuels have promoted extensive research on biofuels. <a>Algal biofuels have been considered as a promising and environmentally friendly renewable energy source</a>. However, several limitations have inhibited the development of cost-effective biofuel production, which includes unstable cultivation caused by invading organisms and high cost of lipid extraction. This dissertation aims to investigate photochemical approaches to prevent culture collapse caused by invading organisms and biological approaches for the development of cost-effective lipid extraction methods.</p><p> </p><p>As a chemical-free water treatment technology, ultraviolet (UV) irradiation has been widely applied to inactivate pathogens but has not been used in algal cultivation to control invading organisms. To evaluate the potential of using UV irradiation to control invading algal species and minimize virus predation, <i>Tetraselmis sp. </i>and <i>Paramecium bursaria Chlorella virus 1</i> (PBCV-1) were examined as challenge organisms to evaluate effectiveness of UV disinfection. The concentration of viable (reproductively/infectively active) cells and viruses were quantified by a most probable number (MPN) assay and a plaque assay. A low-pressure collimated-beam reactor was used to investigate UV₂₅₄ dose-response behavior of both challenge organisms. A medium-pressure collimated-beam reactor equipped with a series of narrow bandpass optical filters was used to investigate the action spectra of both challenge organisms. Both challenge organisms showed roughly five log₁₀ units of inactivation for UV₂₅₄ doses over 120 mJ/cm². the most effective wavelengths for inactivation of <i>Tetraselmis</i> were from 254 nm to 280 nm, in which the inactivation was mainly attributed to UV-induced DNA damage. On the contrary, the most effective wavelength for inactivation of PBCV-1 was observed at 214 nm, where the loss of infectivity was mainly attributed to protein damage. These results provide important information for design of UV reactors to minimize the impact of invading organisms in algal cultivation systems.</p><p> </p><p>Additionally, a virus-assisted cell disruption method was developed for cost-effective lipid extraction from algal biomass. Detailed mechanistic studies were conducted to evaluate infection behavior of <i>Chlorovirus </i>PBCV-1 on <i>Chlorella sp.</i>, impact of infection on mechanical strength of algal cell wall, lipid yield, and lipid distribution. Viral disruption with multiplicity of infection (MOI) of 10^-8 completely disrupted concentrated algal biomass in six days. Viral disruption significantly reduced the mechanical strength of algal cells for lipid extraction. Lipid yield with viral disruption increased more than three times compared with no disruption control and was similar to that of ultrasonic disruption. Moreover, lipid composition analysis showed that the quality of extracted lipids was not affected by viral infection. The results showed that viral infection is a cost-effective process for lipid extraction from algal cells as extensive energy input and chemicals required by existing disruption methods are no longer needed.</p><p> </p><p>Overall, this dissertation provides innovative approaches for the development of cost-efficient algal biofuels. Application of UV disinfection and viral disruption significantly reduces chemical consumption and improves sustainability of algal biofuel production.<br></p>

A utilização descontrolada de pesticidas tem provocado no decorrer dos anos a intoxicação de milhares de pessoas no mundo, uma vez que, seus resíduos têm sido depositados em alimentos, em solos e em ambientes aquáticos. Assim, a construção de duas novas plataformas sensoras para a detecção de pesticidas é o objetivo desse trabalho. Na primeira plataforma foi utilizado o polieletrólito catiônico polietilenoimina (PEI) em conjunto com o polissacarídeo extracelular algal (PSE) produzido pela microalga criptofícea Cryptomonas tetrapirenoidosa preparados através da técnica de deposição \"spin-coating\". E a segunda plataforma foi produzida por eletrodeposição pulsada, entre um potencial de redução e um de oxidação, utilizando nanoestruturas de óxido de zinco (ZnO). Para caracterizar as plataformas, foram utilizadas as técnicas de microscopia eletrônica de varredura com fonte de emissão de campo (FEG-SEM), difração de raios X (XRD), espectroscopia de absorção ultravioleta-visível (UV-Vis), microscopia de força atômica (AFM) e espectroscopia de reflexão-absorção no Infravermelho com modulação da polarização (PM-IRRAS). Através da imobilização da enzima polifenol oxidase na forma de extrato bruto em sua fonte natural (fruto abacate), as plataformas de PEI/PSE e ZnO, foram avaliadas como biossensores de catecol e do inseticida carbaril. De modo comparativo, as plataformas de PEI/PSE sem a presença imobilizada da enzima também foram estudadas para a detecção do catecol e do carbaril. A simplicidade na formação e na construção dessas plataformas vem qualificá-las como viáveis a serem produzidas em escala industrial e com baixo custo de processamento. E diante dos resultados obtidos no desenvolvimento desses biossensores destaca-se a eficiência e a rapidez de detecção, o que os tornam economicamente promissores e competitivos em termos de aplicações ambientais. / The uncontrolled use of pesticides has resulted over the years the intoxication of thousands of people in the world, since their waste has been deposited in food, in soil and aquatic environments. Thus, the construction of two new sensors platforms for pesticide detection is the objective of this work. At first platform was used cationic polyelectrolyte polyethyleneimine (PEI) along with the extracellular algal polysaccharide (EPS) produced by microalgae criptofícea Cryptomonas tetrapirenoidosa prepared by deposition technique \"spin-coating\". The second platform was produced by pulsed electrodeposition between a reduction and an oxidation potential using nanostructures zinc oxide (ZnO). To characterize the platforms, we used the techniques of field emission gun scanning electron microscopy (FEG-SEM), X-ray diffraction (XRD), ultraviolet visible absorption spectroscopy (UV-Vis), atomic force microscopy (AFM), and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). By immobilization of the polyphenol oxidase enzyme as a crude extract in their natural source (avocado fruit), platforms PEI/PSE and ZnO, they were evaluated as catechol and carbaryl insecticide biosensors. In a comparative way, the platforms PEI/PSE without the presence of immobilized enzyme were also studied for detection of catechol and carbaryl. The simplicity in the formation and construction of these platforms comes qualify them as viable to be produced on an industrial scale and low cost processing. And on the results obtained in the development of such biosensors stand out the efficiency and speed of detection, which make them economically promising and competitive in terms of environmental applications.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 201-227).

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (January 19, 2010) Includes bibliographical references (p. 32-33)

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references.

Thesis (Ph. D.)--University of California, Los Angeles, 2003. / Vita. Includes bibliographical references.

A utilização descontrolada de pesticidas tem provocado no decorrer dos anos a intoxicação de milhares de pessoas no mundo, uma vez que, seus resíduos têm sido depositados em alimentos, em solos e em ambientes aquáticos. Assim, a construção de duas novas plataformas sensoras para a detecção de pesticidas é o objetivo desse trabalho. Na primeira plataforma foi utilizado o polieletrólito catiônico polietilenoimina (PEI) em conjunto com o polissacarídeo extracelular algal (PSE) produzido pela microalga criptofícea Cryptomonas tetrapirenoidosa preparados através da técnica de deposição \"spin-coating\". E a segunda plataforma foi produzida por eletrodeposição pulsada, entre um potencial de redução e um de oxidação, utilizando nanoestruturas de óxido de zinco (ZnO). Para caracterizar as plataformas, foram utilizadas as técnicas de microscopia eletrônica de varredura com fonte de emissão de campo (FEG-SEM), difração de raios X (XRD), espectroscopia de absorção ultravioleta-visível (UV-Vis), microscopia de força atômica (AFM) e espectroscopia de reflexão-absorção no Infravermelho com modulação da polarização (PM-IRRAS). Através da imobilização da enzima polifenol oxidase na forma de extrato bruto em sua fonte natural (fruto abacate), as plataformas de PEI/PSE e ZnO, foram avaliadas como biossensores de catecol e do inseticida carbaril. De modo comparativo, as plataformas de PEI/PSE sem a presença imobilizada da enzima também foram estudadas para a detecção do catecol e do carbaril. A simplicidade na formação e na construção dessas plataformas vem qualificá-las como viáveis a serem produzidas em escala industrial e com baixo custo de processamento. E diante dos resultados obtidos no desenvolvimento desses biossensores destaca-se a eficiência e a rapidez de detecção, o que os tornam economicamente promissores e competitivos em termos de aplicações ambientais. / The uncontrolled use of pesticides has resulted over the years the intoxication of thousands of people in the world, since their waste has been deposited in food, in soil and aquatic environments. Thus, the construction of two new sensors platforms for pesticide detection is the objective of this work. At first platform was used cationic polyelectrolyte polyethyleneimine (PEI) along with the extracellular algal polysaccharide (EPS) produced by microalgae criptofícea Cryptomonas tetrapirenoidosa prepared by deposition technique \"spin-coating\". The second platform was produced by pulsed electrodeposition between a reduction and an oxidation potential using nanostructures zinc oxide (ZnO). To characterize the platforms, we used the techniques of field emission gun scanning electron microscopy (FEG-SEM), X-ray diffraction (XRD), ultraviolet visible absorption spectroscopy (UV-Vis), atomic force microscopy (AFM), and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). By immobilization of the polyphenol oxidase enzyme as a crude extract in their natural source (avocado fruit), platforms PEI/PSE and ZnO, they were evaluated as catechol and carbaryl insecticide biosensors. In a comparative way, the platforms PEI/PSE without the presence of immobilized enzyme were also studied for detection of catechol and carbaryl. The simplicity in the formation and construction of these platforms comes qualify them as viable to be produced on an industrial scale and low cost processing. And on the results obtained in the development of such biosensors stand out the efficiency and speed of detection, which make them economically promising and competitive in terms of environmental applications.

No description available.

No description available.

Microalgae synthesize and store large volumes of lipids (potentially over 25% of dry weight) which could provide a renewable source of biodiesel. Traditional extraction techniques often produce poor lipid yields particularly from microalgae with robust cell walls. This project investigated the role of power ultrasound as a cell disruption step in lipid extraction from four microalgal species. Nile Red staining was used to assess the time when ultrasound induced increased membrane permeability in each species and lipids were extracted using an ultrasound assisted Bligh and Dyer extraction method. A 20 kHz probe system (40% amplitude, 0.086 W/cm3) caused increased lipid recovery from dry biomass in all cases; D. salina (no cell wall) from 15 to 22.5% of dry biomass after 1 minute (26% when stressed with 35 g/L NaCl). C. concordia (thin cell wall) from 7.5 to 10.5% of dry biomass after 2 minutes (27% with 25% nitrogen reduction in growth media). N. oculata (thick cell wall) from 6.5 to 10% of dry biomass after 16 minutes (31.5% when stressed with 30 g/L NaCl). The stressed cultures yield could be improved to 35% when ultrasound was combined with S070 beating beads. Chlorella sp. (thick cell wall) from 6.3 to 8.7% of dry biomass, after 16 minutes (44% was achieved when harvested at day 9 instead of 15). A Dual Frequency Reactor (16 and 20 kHz, 0.01 W/cm3) flow system with S070 beads demonstrated that high lipid extraction yields could be achieved on a larger level with N. oculata. After 4:48 minutes sonication 24% lipid recovery was achieved. This system could theoretically increase daily microalgal oil production from 3.96 to 5.76 L per day when compared to conventional techniques, at an extra production cost of only 2.9 p/litre (1.5% increase). D. salina, N. oculata and C. concordia resumed normal growth following sonication at 20 kHz after 1-20 days (8 minutes treatment for D. salina, 60 minutes treatment for N. oculata and 16 minutes treatment for C. concordia). It was found that the supernatant of sonicated D. salina and C. concordia when added to established cultures were able to boost their growth.