As águas continentais existem em menor quantidade na superfície terrestre e apresentam grande importância para a sobrevivência dos seres vivos, motivo pelo qual a preocupação com sua qualidade aumenta a cada dia. As represas de Paraibuna e Paraitinga, localizadas no município de Paraibuna, São Paulo, totalizam 224 km2 de extensão de espelho d´água, com função atual de geração de energia elétrica. Com o objetivo de analisar a qualidade da água destas represas, o presente trabalho apresenta um diagnóstico físico, químico, bem como biológico, no qual foi utilizada a comunidade fitoplanctônica e cálculos de índices de qualidade. Foram realizadas quatro coletas em nove pontos de amostragem distribuídos ao longo das represas. As análises físicas e químicas da água demonstraram baixas concentrações de nutrientes como nitrato (média 0,42 +/- 0,23 mg.L-1) e fosfato (<0,05 mg.L-1). A maior parte dos metais e elementos-traço analisados mostraram-se dentro dos limites estabelecidos pela legislação federal. O elemento fósforo apresentou valores acima (média 0,0293 +/- 0,0153 mg.L-1) do estabelecido pela resolução CONAMA 357/05 (0,020 mg.L-1) em todos os pontos de amostragem no mês de maio, porém este fato pareceu não influenciar a densidade fitoplanctônica. Altos valores de oxigênio dissolvido e transparência, baixos valores de turbidez, condutividade e sólidos dissolvidos, pH próximo à neutralidade, em conjunto com altos índices de diversidade e baixos índices de dominância fitoplanctônica, com predomínio de clorofíceas, demonstraram que as represas estudadas ainda mantêm características de ambiente aquático preservado. Porém, a presença, ainda que em baixas densidades, de cianofíceas e a existência de atividades de monocultura e pecuária no entorno destas represas merecem especial atenção no que tange ao seu correto manejo para que não se tornem fatores prejudiciais à qualidade daquelas águas. / The inland waters are less on the Earth\'s surface and are extremely important for the survival of living things, why the concern for quality increases daily. The dams Paraibuna and Paraitinga, located in Paraibuna city, state of São Paulo, totaling 224 km2 of extension of water surface, with the current function of generating electricity. In order to analyze the water quality of these dams, this paper presents a diagnostic physical, chemical, and biological, which was used in the phytoplankton community and calculation of quality indexes. Four samples were taken at nine sampling points distributed along the dams. The physical and chemical analysis of water showed low concentrations of nutrients such as nitrate (mean 0,42 +/- 0,23 mg.L-1) and phosphate (<0,05 mg.L-1). Most metals and trace elements analyzed were within the limit established by federal law. The element phosphorus (mean 0,0293 +/- 0,0153 mg.L-1) is presented above the values established by CONAMA Resolution 357/05 (0,020 mg.L-1) on all sampling points in the month of May, but this fact did not seem to influence the phytoplankton amount. High levels of dissolved oxygen and transparency, low levels of turbidity, conductivity and dissolved solids, pH close to neutrality, together with high diversity and low dominance of phytoplankton, with a predominance of green algae, showed that the dams still retain features of aquatic environment preserved, which suffer little influence of anthropogenic factors. However, the presence, even at low densities, of cyanobacteria and the existence of plantations and livestock activities in the borders of these dams deserve special attention in terms of their correct management to not become harmful factors to the quality of those waters.

Com a finalidade de compreender a estrutura e a dinâmica da comunidade de algas perifíticas aderidas à Eichhornia azurea Kunt em lagoas marginais, um estudo foi realizado na zona de desembocadura do rio Paranapanema na represa de Jurumirim, em dois locais distintos (região de entrada e região lêntica) de duas lagoas marginais. As coletas foram realizadas mensalmente, no período de um ano (março/01 a março/02) e características climatológicas e hidrodinâmicas, os aspectos físicos e químicos da água, bem como as variáveis biológicas do perifíton, também foram realizadas. As variáveis que apresentaram correlações mais significativas foram: a precipitação, a temperatura da água, o nível da água, a profundidade, a transparência, o pH, a condutividade, a alcalinidade, o CO2 total, CO livre, o material em suspensão total e o inorgânico. De acordo com os índices de classificação, a comunidade perifítica apresentou predominância de biomassa baixa, conteúdo de material inorgânico-orgânico e heterotrofia. Considerando-se as duas lagoas com suas estações de amostragens, foram encontrados 408 táxons. A lagoa do Coqueiral apresentou uma maior riqueza (394 táxons), sendo que a classe Zygnemaphyceae teve o maior número de táxons, (118) e a lagoa do Camargo apresentou 353 táxons, onde também a classe Zygnemaphyceae teve o maior número de táxons, (114). Nas duas estações da lagoa do Camargo e na estação 1 da lagoa do Coqueiral a classe que apresentou maior densidade durante todo o período foi a classe Bacillariophyceae (com dominância da espécie Achnanthidium minutissimum) e na estação 2 da lagoa do Coqueiral nos meses de abril e maio de 2001 a classe Oedogoniophyceae teve uma maior densidade e em novembro a classe Cyanophyceae teve uma contribuição de 63,4% na densidade total. Os valores de diversidade de Shannon-Weaner foram maiores na entrada da lagoa do Coqueiral variando de 2,37 bits/ind.(ago/01) a 5,20 bits/ind. (mar/02). Os táxons que tiveram 100% de freqüência relativa foram: Achnanthidium minutissimum, Cymbella minuta, Eunotia sp, Fragilaria capucina, Cosmarium margaritatum, Cosmarium regnellii, Cosmarium sp, Bulbochaete sp e Oedogonium sp. A lagoa do Coqueiral, com maior conectividade com o rio, apresentou maior diversidade e riqueza enquanto que na lagoa do Camargo, ocorreu maior densidade. / Aiming to understand structure and dynamics of periphytic algae attached to Eichhornia azurea Kunt in marginal lakes, a study was undertaken at the mouth zone of Paranapanema river in Jurumirim reservoir, at two distinct locations (entrance region and lentic region) of two marginal lakes. Samplings were taken monthly, during one year (March/01 to March/02), climatological and hydrodynamic characteristics, physical and chemical aspects, as well as periphyton biological variables, were also studied. The variables with more meaningful correlations were: precipitation, water temperature, water level, depth, transparency, pH, conductivity, alkalinity, total CO2, free CO, total and inorganic suspended matter. According to the classification indexes, periphytic community presented a low biomass predominance, inorganic-organic matter content and heterotrophy. Considering the two lakes with its sampling stations, 408 taxa were found. Coqueiral lake presented greater richness (394 taxa), and the class Zygnemaphyceae had more taxa than the others (118), and Camargo lake presented 353 taxa, where the class Zygnemaphyceae also had more taxa (114). In both sampling stations from Camargo lake, and in station 1 from Coqueiral lake, the class with higher density during the whole period was Bacillariophyceae (with the dominance of the species Achnanthidium minutissimum), and in station 2 from Coqueiral lake in the months of April and May, 2001 the class Oedogoniophyceae hadgreater density and in November the class Cyanophyceae contributed in 63,4% of total density. Shannon-Weaner diversity values were higher at the entrance/mouth of Coqueiral lake, varying from 2.37 bits/ind (August/01) to 5.20 bits/ind (March/02). The taxa that had 100% of relative frequency were: Achnanthidium minutissimum, Cymbella minuta, Eunotia sp, Fragilaria capucina, Cosmarium margaritatum, Cosmarium regnellii, Cosmarium sp, Bulbochaete sp and Oedogonium sp. Coqueiral lake, with more connectivity to the river, presented higher diversity, while in Camargo lake density was higher.

Devido à sua importância ecológica e econômica as algas gracilarióides são alvo de diversos estudos desenvolvidos por pesquisadores de todo o mundo. No entanto, ainda persistem dificuldades em relação à taxonomia do grupo, que se tornam ainda mais problemáticas no que diz respeito às espécies achatadas, ainda pouco estudadas quando comparadas às espécies cilíndricas. Essa dificuldade taxonômica é devida principalmente a um elevado número de espécies, algumas com ampla distribuição geográfica e a morfologia simples e plástica. Devido à grande dificuldade em se identificar as espécies de Gracilariaceae utilizando-se caracteres morfológicos, o uso de dados moleculares tem se mostrado taxonomicamente útil, e em alguns casos essencial, na discriminação das espécies. Neste trabalho foram geradas sequências inéditas de dois marcadores moleculares do tipo DNA \"barcodes\" (UPA e cox1) para diversas espécies, incluindo espécies de ocorrência na costa brasileira e algumas espécies de outras localidades mantidas em cultura no Banco de Germoplasma da USP. A morfologia para os táxons encontrados foi analisada e o gene rbcL foi sequenciado para permitir a comparação com outras sequências nos bancos de dados e para a construção de uma filogenia para o grupo. Foram geradas 289 sequências para 135 amostras. DNA \"barcodes\" foram gerados para todas as 50 amostras do banco de germoplasma. Em adição, o rbcL foi sequenciado para os agrupamentos de cox1/UPA totalizando 14 amostras. Treze espécies diferentes foram identificadas no banco de germoplasma combinando análises morfológicas anteriores e análises moleculares. Nossas análises indicaram que cox1 e UPA foram marcadores eficientes para a delineação das espécies de Gracilariaceae e tornaram o banco ainda mais útil para pesquisas futuras. Em relação às espécies de Gracilariaceae de ocorrência na costa brasileira, a utilização dos marcadores moleculares permitiu a identificação de alguns táxons, dos quais três são novas ocorrências para o Brasil: Gracilaria damaecornis, Gracilaria hayi e Gracilariopsis Silvana. Baseado em dados morfológicos e moleculares concluímos que Gracilaria tepocensis citada para a região Sul e Sudeste, não ocorre no Brasil tratando-se de Gracilaria isabellana, anteriormente citada para o Brasil como Gracilaria lacinulata. Concluímos também que os marcadores moleculares do tipo DNA \"barcode\" são eficientes na identificação das Gracilariaceae de talo cilíndrico cujos caracteres morfológicos diagnósticos pouco contribuem no reconhecimento: Gracilaria birdiae, Gracilaria caudata e Gracilaria córnea, ao contrário de estudos pretéritos que utilizaram outros marcadores moleculares mais conservados (SSU rDNA). A utilização de ferramentas moleculares na identificação e separação das Gracilariaceae de talo achatado mostrou-se bastante eficiente e necessária, uma vez que os caracteres morfológicos de valor taxonômico pouco contribuem na correta identificação. Dessa forma foi possível identificar 19 táxons de Gracilariaceae utilizando-se marcadores moleculares, dos quais 15 correspondem as Gracilariaceae de talo achatado / Due to its ecological and economic importance gracilarioid algae are targets of several studies developed by researchers around the world. However, there are still difficulties for the taxonomy of this group, which become even more problematic with regard to the flattened species, which are poorly studied species when compared to cylindrical. This taxonomic difficulty is primarily due to a high number of species, some with broad geographic distribution and a simple and plastic morphology. Due to great difficulty in identifying the species of Gracilariaceae using morphological characteristics, molecular data has shown to be taxonomically useful, and in some cases essential to discriminate species. In this study we generated novel sequences of two DNA \"barcodes\" (UPA and cox1) molecular markers for several species, including species occurring on the Brazilian coast and some species from other localities maintained in culture in the Germplasm Bank of USP. The morphology of the taxa was analyzed and the rbcL gene was sequenced to enable comparison with other sequences in the databases and to construct a phylogeny for the group. A total of 289 sequences were generated for 135 samples. DNA \"barcodes\" were generated for all 50 samples of the germplasm bank. In addition, the rbcL was sequenced for 14 representatives of the cox1/UPA groups. Thirteen different species were identified in the germplasm bank combining previous morphological and molecular analyses. Our analysis indicated that cox1 and UPA markers were efficient for the delineation of Gracilariaceae species and made the bank even more useful for future research. Regarding Gracilariaceae species occurring on the Brazilian coast, the use of molecular markers allowed the identification of some taxa, of which three are new records for Brazil: Gracilaria damaecornis, Gracilaria hayi and Gracilariopsis silvana. Based on morphological and molecular data Gracilaria tepocensis cited for the South and Southeast of Brazil does not occur, and is in fact Gracilaria isabellana previously cited for Brazil as Gracilaria lacinulata. We also conclude that the DNA \"barcode\" molecular markers are effective in identifying Gracilariaceae presenting cylindrical thallus whose diagnostic morphological characters little contribute for its recognition: Gracilaria birdiae, Gracilaria caudate and Gracilaria cornea, unlike other studies that used more conserved molecular markers (SSU rDNA). The use of molecular tools in the identification and separation of flattened Gracilariaceae proved to be very efficient and necessary, since the morphological characters contribute little for the correct identication. Thus, in this work it was possible to identify 19 taxa of Gracilariaceae using molecular markers, of which 15 corresponds flattened species

The global demand and sustainability concerns for producing light olefins encouraged researchers to look for an alternative and sustainable feedstock. Alkenes, such as ethene, propene and butene, are known as light olefins. Olefins are the backbone of the chemical industry because they serve as the chemical building blocks for the manufacture of polymers, fibers, and numerous organic chemicals. Feedstocks such as naphtha, natural gas and liquefied petroleum gas (LPG) are currently used for producing light olefins, but they are non-renewable and hence unsustainable. In contrast, biomass as a potential feedstock for the production of fuels and chemicals is renewable. Microalgae, in particular, are a promising resource due to their fast growth rate and ability to act as a CO2 sink. The objective of my research was to assess the potential of thermochemical production of the light olefins ethene, propene, and butene from the marine microalga Nannochloris oculata in the absence and presence of catalysts and study the effect of catalyst to cell mass ratio on the production of these chemicals. Thermal cracking was conducted using two catalysts, aluminosilicate (Si/Al) and H-ß zeolite at 400-650 °C in a semi-batch reactor system and gas analysis was performed using mass spectrometry. Cracking of N. oculata by the aluminosilicate catalyst was studied in more detail at catalyst-to-algae mass ratios of zero, 5:1, 10:1 and 20:1 using (Si/Al) catalyst and a comparative study was performed at catalyst-to-algae mass ratio of 10:1 using (Si/Al) and H-ß zeolite catalyst. The formation of light olefins ethene, propene, and butene was quantified. Higher temperature and catalyst to algae ratio led to an increase in the yield of all olefins, although a diminishing effect was observed above 600 °C and a ratio of 5:1. Although ethene was the most significant product, the concentration of all olefins increased significantly, when catalysts were employed in the cracking reaction. Moreover, the comparative study revealed that ethene was the most significant product when (Si/Al) was used and propene was the most significant product when H-ß zeolite was used.

To date, limited research has been conducted on the effects of cytotoxic drugs on aquatic species. Three of these species, a single celled plant, an invertebrate and a fish, were exposed to six cytotoxic drugs, both singly and as simple mixtures. A range of endpoints were assessed, including growth inhibition in algae, immobilisation in daphnia and the impact on organ size and the expression of the DNA damage repair genes RAD51 and p53 in zebrafish. No effects at environmentally relevant concentrations were observed in any of the three species.

The aim of this study was to evaluate the nutritional value of algae and zooplankton grown in an algal integrated ponding system for poeciliids. The available information on the nutritional requirements of poeciliids was compared with a proximate analysis of the algae and zooplankton. The effluent grown algae and zooplankton had a crude protein value of 41.47 ± 0.2% and 36.84 ± 0.3%, a lipid content of 4.8 ±. 0.4% and 11.1 ± 0.8% and a carbohydrate content of 35.13 ± 0.8% and 31.06 ± 0.6% respectively. These values compared favourably with those of the known nutritional requirements of poeciliids. To test if the nutritional value of the algae and zooplankton in the AlPS was constant, the species composition of the algae and the crude protein content of the algae and zooplankton in the high rate oxidation ponds were measured monthly and bi-weekly for a year respectively. The species composition remained fairly stable for the duration of the experiment and the average protein composition of the algae and zooplankton was 43.4 ± 4.4% and 38.6 ±2.8% respectively. This indicated that the algae and zooplankton in the AlPS provided high protein biomass through the year. The quality of the effluent grown algal and zooplankton biomass was evaluated by analysing their amino acid composition and comparing it with the amino acid composition of the body tissue of X. helleri. With respect to the amino acid composition of the body tissue of X. helleri, the amino acid profile of the algae had a 69% and the zooplankton a 63% similarity. The quality of the pure algal and zooplankton protein was also tested biologically, by feeding them directly to poeciliids during a ten week growth trial. The algae and zooplankton diets did not result in adequate growth compared to poeciliids which were fed a formulated control diet. The initial growth trial also evaluated the effect of processing on the chemical composition of the algae and its biological effect on fish fed with it. There were no significant differences in the chemical composition of fresh and sun dried algae and this was reflected in the growth rates of the fish which did not differ significantly. Freeze dried algae had a lower crude protein content than fresh and sun dried algae and a poorer amino acid composition. Fish fed freeze dried algae exhibited poorer growth and survival in comparison to the other treatments. The gut transit times of X. helleri and the gastric evacuation times of poeciliids were determined using colour dyes incorporated in the diet and by sacrificing fish at predetermined intervals after feeding respectively. The gut transit time of X. helleri fed a sun dried algal diet and a formulated diet was 225 ± 8.55 minutes and 261.93 ± 10.86 minutes respectively. The gastric evacuation times of X. helleri, P. reticu/ata and P. velifera were 7, 9 and 8 hours respectively. Since the maximum amount of food in the hindgut after feeding was detemined to be 3, 5 and 3 hours in X. helleri, P. reticulata and P. velifera respectively, fish were sacrificed at these times in the digestibility study. The digestibility of sun dried algae was determined using 1 % chromic oxide as an internal marker in the algae. The apparent crude protein digestibility of sun dried effluent grown algae ranged from 65%-75% in the three poeciliid species. Based on the results of the chemical and biological analysis of the algae and zooplankton, conventional diets incorporating algae at 5% and 20% protein inclusion levels were formulated. These diets and a treatment in which zooplankton, reared in the AlPS were fed as a dietary supplement to a formulated diet were fed to poeciliids for twelve weeks. No significant differences in the growth of poeciliids fed any of the test diets were observed. It was concluded that the algae could be incorporated into poeciliid formulated diets up to level of 20% protein inclusion without any negative effect on the growth of the fish. The chemical and biological evaluation of the algae suggested that it had a similar nutritional quality to soyabean meal. Poeciliid growth was not enhanced with a zooplankton supplement, however a possible low feeding rate by poeciliids on the zooplankton as a result of their small size may have affected the result. The colour enhancement potential of effluent grown algae and zooplankton was evaluated biologically in ten and twelve week growth trials using visual observation (31 people) and by using a chromameter. While pure, sun dried algae significantly enhanced the colour of P. reticulata, no significant differences in the colour of poeciliids were observed or recorded when fish were fed diets incorporating sun dried algae up to levels of 20% protein inclusion. The effect of effluent grown algae and zooplankton on poeciliid health was also tested biologically in the ten and twelve week growth trials. The high mortalities (75%-84%) recorded for X. hel/eri when fed the pure algal and zooplankton diets were considered to be as a result of the nutritional inadequacy of the diets since there were significantly less mortalities in fish fed the formulated control diet and 63% of the fish that died during the course of the trial were emaciated. In addition, fewer mortalities (10%-40%) were recorded in X. hel/eri fed the nutritionally adequate formulated diets in the twelve week growth trial. No symptoms of disease were recorded in the twelve week growth trial and the algae was considered to have no toxicological or pathological effects on poeciliids. Centrifugation, sand filtration, sedimentation, microstraining and biological harvest were evaluated as methods of small scale algal harvest from the high rate oxidation ponds. Algae could be harvested most efficiently with little associated labour by sedimentation (without flocculating agents) and by microstraining with 60IJm mesh. Effluent grown algae can replace conventional feed ingredients up to a level of 20% protein inclusion without negatively effecting the growth, colour, health or survival of poeciliids.

Breast cancer remains the leading cause of cancer-related death in women worldwide. Furthermore, it has been demonstrated that the treatment-resistant ER-PR-HER2/neu- sub-type is more common among women of African descent, necessitating the search for novel chemotherapies for this form of the disease. The secondary metabolites produced by marine algae represent a rich source of structurally unique compounds with chemotherapeutic potential, particularly in South Africa, whose oceans allegedly host 15 % of the total number of species in the world. Indeed, a recent study reported the isolation of a range of novel compounds from South African red and brown algae of the Plocamium, Portiera and Sargassum genera which displayed cytotoxicity against oesophageal cancer cells in vitro. The molecular mechanisms mediating this toxicity were unknown, as was the effect of these and similar compounds on metastatic ER-PR-HER2/neu- breast cancer cell lines or breast cancer stem cells. The current study aimed to address these questions by screening a library of twenty-two novel marine algal compounds for the ability to inhibit MDA-MB-231 and Hs578T breast cancer cells, while having no adverse effects on non-cancerous MCF12A breast epithelial cells. While twelve of these were toxic in the micromolar range against breast cancer cells, only the polyhalogenated monoterpenes RU004 and RU007, and the tetraprenylated quinone sargaquinoic acid (SQA) were identified as hit compounds based on the criteria that their cytotoxicity was specific to breast cancer and not healthy breast cells in vitro. On the other hand, the halogenated monoterpene RU015 was found to be highly toxic to both breast cancer and non-cancerous breast cell lines, while the halogenated monoterpene stereoisomers RU017 and RU018 were non-toxic to either of these cell lines. The mode of action of RU004, RU007, RU015 and SQA, together with the previously characterized carotenoid fucoxanthin (FXN), was assessed in terms of the type of cell death induced and the effect on cell cycle distribution of these compounds. Flow cytometric analysis of the extent of Hoescht 33342 and propidium iodide staining along with PARP cleavage studies suggested that SQA induced apoptosis in MDA-MB-231 cells. On the other hand, the highly toxic compound RU015 appeared to induce necrosis as evidenced by 50 kDa PARP cleavage product in MDA-MB-231 cells. The flow cytometry profiles of MDA-MB-231 and Hst578T cells treated with the hit compounds RU004 and RU007 were suggestive of the induction of apoptosis by these compounds. Cell cycle analysis by flow cytometry with propidium iodide staining revealed that both SQA and FXN induced G0-G1 arrest together with an increase in the apoptotic sub-G0 population, which agreed with previous reports in the literature. The molecular mechanism of action of SQA and FXN were further investigated by the identification of specific signal transducer molecules involved in mediating their anti-cancer activities. SQA was found to require the activity of numerous caspases, including caspase-3, -6, -8, -9, -10 and -13, for its cytotoxicity and was demonstrated to decrease the level of the antiapoptotic protein Bcl-2. On the other hand, FXN was shown to require caspase-1, -2, -3, -9 and - 10 for its toxicity. This, together with the ability to decrease the levels of Bcl-2, pointed to the involvement of the intrinsic pathway in particular in mediating the activity of FXN. The screening of algal compounds against non-cancerous breast epithelial cells carried out in this study, together with the investigation into their mechanisms of action, represent one of the few reports in which characterization of algal metabolites goes beyond the initial cytotoxicity assays. Finally, in order to assess the potential anti-cancer stem cell activity of the marine algal compounds, a subset of these was screened using a mammosphere assay technique developed in this study. The cancer stem cell (CSC) theory proposes that cancers arise from and are maintained by a specific subpopulation of cells able to undergo asymmetric cell division and termed CSCs. These CSCs are capable of anchorage-independent growth in serum-free culture conditions, such as those in the mammosphere assay. Using this assay, the novel halogenated monoterpene stereoisomers RU017 and RU018 were demonstrated to possess putative anti- CSC activity as evidenced by their ability to completely eliminate mammosphere formation in vitro. Furthermore, since RU017 and RU018 were non-toxic to both breast cancer and healthy breast cells, it appeared that the activity of the compounds was potentially specific to the CSCs. The results require further validation, but represent the first report of selective anti-CSC activity.

The objective of this project was to treat petroleum refinery wastewater using a combination of anaerobic and aerobic processes, namely an Up-flow Anaerobic Sludge Blanket (UASB) reactor paired with a Rotation Algae Biofilm Reactor (RABR), respectively, to produce a treated effluent. The treatment method developed needed to produce a cost-effective and efficient way to decrease nitrogen, phosphorous, total suspended solids (TSS), and COD concentrations to below State of Utah limitations. It was demonstrated that RABR treatment was capable of reducing effluent concentrations of nitrogen, phosphorus, and TSS to State of Utah limitations. RABR treatment did not significantly reduce COD from the wastewater. The COD reduction requirement, however, was met through anaerobic digestion of the wastewater. Therefore, our system proved effectual at the treatment of the wastewater and met all design criteria.

La photosynthèse consiste en la conversion photo-induite du dioxyde de carbone et de l'eau en matière organique et en dioxygène. Utilisée par les algues, les plantes ou certaines bactéries, la photosynthèse est pourtant intrinsèquement bridée puisque seulement 4 % de l'énergie lumineuse sont convertis en énergie chimique. Sous forte irradiation, ceci peut engendrer une dénaturation de l'appareil photosynthétique. Par ailleurs, dans le contexte environnemental actuel, cette limitation représente également une opportunité d'utiliser l'énergie non convertie sous forme d'énergie électrique. Le travail présenté dans ce manuscrit a donc pour but de créer une voie secondaire d'écoulement des électrons photosynthétiques excédentaires afin de réduire l'endommagement du système sous forte irradiation et de les transcrire sous la forme d'un photo-courant. C'est pourquoi un système impliquant une électrode collectrice de carbone et des médiateurs redox de type quinone a été envisagé. La capacité acceptrice de certaines quinones, connues pour être de bons accepteurs du Photosystème II, a été évaluée au moyen d'études de fluorescence. La facilité de restitution des électrons dérivés par les quinones réduites a été quant à elle étudiée par électrochimie. Au bilan, les meilleures quinones (DCBQ, PPBQ) permettent d'obtenir des photo-courants de l'ordre de quelques µA.cm-2. La corrélation entre données expérimentales et théorie a également permis de mieux cerner le mécanisme de dérivation des électrons photosynthétiques par les quinones exogènes mais aussi de mettre en évidence des effets d'empoisonnement et/ou de perte d'accepteur dans les membranes. / Photosynthesis can be views as the conversion of carbon dioxide and water into organic matter and dioxygen. Used by algae, plants or some bacteria, photosynthesis efficiency is limited because only 4% of light energy is converted into chemical energy. Under high light conditions, this can induce serious damages of the photosynthetic machinery. Besides, if considering the current environmental context, this limitation is an opportunity to use the part of not converted energy to generate some useable electricity. The aim of the work developed in this manuscript is thus to create an additional pathway for derivating the photosynthetic electrons flow. In this way, the system damages are expected to be reduced under hight light conditions as well as some photocurrent to be generated. This is why an experimental set-up involving carbon working electrode and some quinone type redox mediators has been developed. The quinone ability to accept some electrons from Photosystem II has been studied by the mean of fluorescence techniques. Their ability to be re-oxidised at the carbon electrode surface has been investigated by cyclic voltametry. As a conclusion, the best quinones (selected after the fluorescence investigations) are DCBQ and PPBQ and correspond to photocurrent values about several µA.cm-2. A correlation between experimental data and theoretical predictions helped us to best understand the photosynthetic electrons derivation pathway and to evidence concomitant phenomenon like poisoning and quinone partition effects.

Acid rmne drainage (AMD) is a major pollution problem througbout the world, adversely affecting both surface and groundwaters. AMD is principally associated with the mining of sulphide ores. The most commonly associated minerals being sulphur, copper, zinc, silver, gold, lead and uranium. As conventional methods for removing heavy metals from wastewater are often prohibitively expensive, the implementation of biological processes for the removal of heavy metals has become a realistic practice. The objectives of this project was firstly to establish the effect of copper, lead and nickel, heavy metals commonly found in AMD waters, on the enzyme carbonic anhydrase, which is an integral part of the carbon concentrating mechanism (CCM) and secondly, to determine the feasibility of using the alkalinity generated by Spindina for the precipitation of heavy metals from solution. Initially, batch flask experiments were performed and it was found that the algae were able to utilise the bicarbonate supplied in the medium, under CO, limiting conditions, through the induction of their CCM, resulting in the generation of carbonate. The effect of the inhibitors, acetazolamide (AZ) and ethoxyzolamide (EZ), were also investigated in order to determine the importance of carbonic anhydrase (CA) in inorganic carbon accumulation and photosynthesis. Results obtained were consistent with those observed in literature and it was found that at IOOf.LM AZ and EZ, complete inhibition of photosynthesis and carbonic anhydrase occurred, with no oxygen being evolved. The results obtained from the inhibitor experiments substantiate the findings that carbonic anhydrase is an important part of the CCM, and that the dehydration of bicarbonate to carbon dioxide and hydroxide ions, is in fact an enzymatic process regulated by the enzyme carbonic anhydrase and is essential for efficient photosynthesis. The effect of heavy metals on Spirulina was also investigated. Lead, copper and nickel were all found to cause a reduction in the synthesis of chlorophyll a, which resulted in a decrease in photosynthetic efficiency and eventually death of the culture. The morphology of the algae was also severely affected by heavy metals, with degradation and aJmost complete disintegration of the algal filaments occurring. Using the Wilbur-Anderson assay method, carbonic anhydrase activity was found to be lower in the experimental flasks containing heavy metals, than the control flasks, reducing the algae's ability to utilise the bicarbonate in solution for effective photosynthesis. The Wilbur-Anderson assay method did not prove to be a reliable method for measuring changes in enzyme activity as results were found to be erratic. Therefore attempts were made to use an oxygen electrode as an alternative method for determining the effects of various parameters on enzyme activity and photosynthesis, this proved to be more successful. Because of the toxic effects of heavy metals on Spirulina it was decided that the use of the biogenic alkalinity generated by the algae for the precipitation of heavy metals may be successfully employed as an alternative method for bioremediation and metal recovery. Carbonate reacts readily with metals, therefore the carbonate produced by this algal system was used for the precipitation of metals. It was possible to categorise the precipitation reactions observed into three groups, namely those metals which, a) precipitate as hydroxides, b) precipitate as carbonates generated from the dissociation of bicarbonate and c) metals which can only precipitate if there is free carbonate present in solution.