Control of predators in industrial scale microalgae cultures with Pulsed Electric Fields.

This work describes the utilization of Pulsed Electric Fields to control the protozoan contamination of a microalgae culture, in an industrial 2.7m3 microalgae photobioreactor. The contaminated culture was treated with Pulsed Electric Fields, PEF, for 6h with an average of 900V/cm, 65μs pulses of 50Hz. Working with recirculation, all the culture was uniformly exposed to the PEF throughout the assay. The development of the microalgae and protozoan populations was followed and the results showed that PEF is effective on the selective elimination of protozoa from microalgae cultures, inflicting on the protozoa growth halt, death or cell rupture, without affecting microalgae productivity. Specifically, the results show a reduction of the active protozoan population of 87% after 6h treatment and 100% after few days of normal cultivation regime. At the same time, microalgae growth rate remained unaffected. © 2014 Elsevier B.V.

Microalgae bio-stimulating effect on traditional tomato agriculture

Máster en Oceanografía

Cultivo da microalga marinha Chaetoceros calcitrans (BACILLARIOPHYCEAE) utilizando diferentes tipos de água marinha artificial

The use of microalgae as live food to a wide variety of organisms is one of the most important aspects in aquaculture. Several commercial formulations have been available in the marine aquarium market in order to prepare artificial sea water (ASW). The present study accounted microalgae Chaetoceros calcitrans performance cultured using different ASW in comparison to natural seawater(NSW). it was carried out using red Sea, Coralife and oceanic, three different ASW brands and NSW as control. nonaerated cultures were grew in 400 mL with Conwy culture medium with five replicates each under defined conditions. All cultures began with an algal inoculum of 208.000 cells/mL. a 5-mL aliquot was removed daily from each culture for cells counts. data obtained using polynomial regression test demonstrated that all ASW brands reached higher algal density rates than the one with NSW, though the three ASW brands were significantly heterogeneous. C. calcitrans raised with oceanic and red Sea brands showed similar growth rates and both were higher than Coralife brand. the results suggest that all three ASW brands studied can be used in the culture of this microalgae specie.

Influence of ammonium sulphate feeding time on fed-batch Arthrospira (Spirulina) platensis cultivation and biomass composition with and without pH control

Previous work demonstrated that a mixture of NH(4)Cl and KNO(3) as nitrogen source was beneficial to fed-batch Arthrospira (Spirulina) platensis cultivation, in terms of either lower costs or higher cell concentration. On the basis of those results, this study focused on the use of a cheaper nitrogen source mixture, namely (NH(4))(2)SO(4) plus NaNO(3), varying the ammonium feeding time (T = 7-15 days), either controlling the pH by CO(2) addition or not. A. platensis was cultivated in mini-tanks at 30 degrees C, 156 mu mol photons m(-2) s(-1), and starting cell concentration of 400 mg L(-1), on a modified Schlosser medium. T = 13 days under pH control were selected as optimum conditions, ensuring the best results in terms of biomass production (maximum cell concentration of 2911 mg L(-1), cell productivity of 179 mg L(-1) d(-1) and specific growth rate of 0.77 d(-1)) and satisfactory protein and lipid contents (around 30% each). (C) 2011 Elsevier Ltd. All rights reserved.

Evaluation of the composition of continuously-cultivated Arthrospira (Spirulina) platensis using ammonium chloride as nitrogen source

This work is focused on the influence of dilution rate (0.08 <= D <= 0.32 d(1)) on the continuous cultivation and biomass composition of Arthrospira (Spirulina) platensis using three different concentrations of ammonium chloride (c(No) = 1.0, 5.0 and 10 mol m (3)) as nitrogen source. At c(No) = 1.0 and 5.0 mol m (3) the biomass protein content was an increasing function of D, whereas, when using c(No) = 10 mol m (3), the highest protein content (72.5%) was obtained at D = 0.12 d (1). An overall evaluation of the process showed that biomass protein content increased with the rate of nitrogen supply (D c(No)) up to 72.5% at D c(No) = 1.20 mol m (3) d (1). Biomass lipid content was an increasing function of D only when the nitrogen source was the limiting factor for the growth (D c(No) <= 0.32 mol m (-3) d (1)), which occurred solely with c(No), = 1.0 mol m (3). Under such conditions, A. platensis reduced its nitrogen reserve in the form of proteins, while maintaining almost unvaried its lipid content. The latter was affected only when the concentration of nitrogen was extremely low (c(No) = 1.0 mol m (3)). The most abundant fatty acids were the palmitic (45.8 +/- 5.20%) and the gamma-linolenic (20.1 +/- 2.00%) ones. No significant alteration in the profiles either of saturated or unsaturated fatty acids was observed with c(No) <= 5.0 mol m (3), prevailing those with 16 and 18 carbons. (C) 2010 Elsevier Ltd. All rights reserved.

Extração e análise da fração lipídica da microalga monoraphidium sp., síntese e caracterização do seu biodiesel

The cultivation of microalgae biomass in order to produce biodiesel arises as an extremely promising aspect, in that the microalgae culture includes short cycle of reproduction, smaller areas for planting and residual biomass rich in protein content. The present dissertation evaluates the performance and features, through spectrometry in the region of infrared with transformed Fourier (FTIR) and spectrometry in the region of UVvisible (UV-Vis), of the extracted lipid material (LM) using different techniques of cell wall disruption (mechanical agitation at low and at high spin and agitation associated with cavitation). The technique of gas chromatography (GC) brought to light the success of alkaline transesterification in the conversion of oil into methyl monoesters (MME), which was also analyzed by spectroscopic techniques (FTIR, proton magnetic resonance (1H NMR) and carbon (13C NMR). Through thermogravimetric analysis (TGA) were analyzed the lipid material (LM), biodiesel and the microalgae biomass. The method which provided the best results concerning the efficiency in extraction of the LP of Monoraphidium sp. (12,51%) was by mechanical agitation at high spin (14 000 rpm), for 2 hours being the ideal time, as shown by the t test. The spectroscopic techniques (1H NMR, 13C NMR and FTIR) confirmed that the structure of methyl monoesters and the chromatographic data (CG) revealed a high content of saturated fatty acid esters (about 70%) being the major constituent eicosanoic acid (33,7%), which justifies the high thermal stability of microalgae biodiesel. The TGA also ratified the conversion rate (96%) of LM into MME, pointing out the quantitative results compatible with the values obtained through GC (about 98%) and confirmed the efficiency of the extraction methods used, showing that may be a good technique to confirm the extraction of these materials. The content of LM microalgae obtained (12,51%) indicates good potential for using such material as a raw material for biodiesel production, when compared to oil content which can be obtained from traditional oil for this use, since the productivity of microalgae per hectare is much larger and requires an extremely reduced period to renew its cultivation

Modeling, characterization and microalgal cultivation in an airlift panel photobioreactors.

Microalgae cultures are attracting great attentions in many industrial applications. However, one of the technical challenges is to cut down the capital and operational costs of microalgae production systems, with special difficulty in reactor design and scale-up. The thesis work open with an overview on the microalgae cultures as a possible answer to solve some of the upcoming planet issues and their applications in several fields. After the work offers a general outline on the state of the art of microalgae culture systems, taking a special look to the enclosed photobioreactors (PBRs). The overall objective of this study is to advance the knowledge of PBRs design and lead to innovative large scale processes of microalgae cultivation. An airlift flat panel photobioreactor was designed, modeled and experimentally characterized. The gas holdup, liquid flow velocity and oxygen mass transfer of the reactor were experimentally determined and mathematically modeled, and the performance of the reactor was tested by cultivation of microalgae. The model predicted data correlated well with experimental data, and the high concentration of suspension cell culture could be achieved with controlled conditions. The reactor was inoculated with the algal strain Scenedesmus obliquus sp. first and with Chlorella sp. later and sparged with air. The reactor was operated in batch mode and daily monitored for pH, temperature, and biomass concentration and activity. The productivity of the novel device was determined, suggesting the proposed design can be effectively and economically used in carbon dioxide mitigation technologies and in the production of algal biomass for biofuel and other bioproducts. Those research results favored the possibility of scaling the reactor up into industrial scales based on the models employed, and the potential advantages and disadvantages were discussed for this novel industrial design.

Desarrollo y validación de tecnologías de intensificación lumínica para fotobiorreactores (FBR) para el aprovechamiento de la radiación en el cultivo de microalgas

En la actualidad la humanidad se enfrenta a una serie de problemas de gran transcendencia que van a determinar en alto grado los niveles de calidad de vida en los próximos años. El calentamiento global, el incremento demográfico incontrolado, la contaminación ambiental y la escasez de recursos así como una mala distribución de los mismos, son sólo algunos ejemplos. En este contexto, las microalgas, microrganismos fotosintéticos de alta eficiencia y versatilidad, presentan una serie de características que las convierten a priori en la base de una tecnología con un enorme potencial para formar parte de la solución a estos graves problemas planteados. Uno de los principales factores que impiden una mayor implantación de la tecnología de microalgas es de tipo económico. La baja productividad por unidad de área de los sistemas de cultivo actuales y la alta inversión necesaria en equipos y mantenimiento, hace que solo se justifique el cultivo de productos de muy alto valor añadido. Las soluciones pasan por aumentar el rendimiento global de los cultivos y por disminuir los costes de equipos e instalaciones. La presente tesis investiga sobre la posibilidad de conseguir un mejor aprovechamiento de la luz solar incidente sobre un cultivo de microalgas mediante el uso de una serie de dispositivos ópticos que vienen a denominarse intensificadores lumínicos. De entre los factores que determinan la productividad de un campo de cultivo de microalgas, posiblemente el más determinante sea la cantidad de radiación que las microalgas pueden aprovechar. Los intensificadores aumentan la disponibilidad de luz en el interior de los tubos de cultivo, de forma que la fotosíntesis se vea favorecida y, de este modo, se incremente la tasa de crecimiento de las microalgas. En el desarrollo de la tesis se proponen tres tipologías diferentes de intensificador diseñadas en base a criterios óptico-geométricos. Para cada una de estas tipologías se evalúa el incremento de radiación que se lograría sobre un tubo de cultivo. Paralelamente se desarrolla un modelo que permite la evaluación de la productividad del cultivo. Esto permite añadir el factor biológico al puramente óptico-físico y valorar las distintas propuestas de intensificadores en función de las características propias del microalga utilizada en el cultivo. El modelo es verificado y contrastado frente a datos de producción obtenidos en la bibliografía. Finalmente, la exposición concluye con una presentación general de las futuras líneas de investigación. ABSTRACT Today, humanity is facing a series of problems of global significance that will determine the standard of living in the years ahead. Global warming, uncontrolled population growth, pollution, lack of resources and poor distribution of them are just an example of the challenges we are facing. In this context, microalgae, high efficient photosynthetic microorganisms, have a number of characteristics that turn them into a very promising technology that can contribute or be part of a sustainable solution. One of the main factors preventing the adoption of microalgae technology is economical. The low productivity per unit area of current farming systems and the high investment needed in equipment and maintenance, only justifies the cultivation of algae for high value applications. One solution could be increasing the overall yield of the crops and reduce the equipment and facilities costs. Among the factors that determine the productivity of a microalgae culture, possibly the most influential one is the amount of radiation that microalgae receive. This Thesis develops the possibility of making better use of the sunlight radiation incident on a crop field using a series of devices similar to solar collectors. The solar collectors proposed are intended to increase the availability of light inside the culture tubes and within it, the tax of photosynthesis and the overall growth rate of the microalgae. In this research, three different configurations of collectors are designed, based on optical and geometrical criteria. For each one of these collectors, the increase on radiation that would be expected is evaluated. Furthermore, a model for light distribution inside the culture is developed in terms to estimate the biomass productivity. This allows adding the biological factor to purely optical-physical considerations and to assess the different solar collectors proposed, in terms specific for the microalgae. The model is tested against production data obtained in different scientific literature. Finally, the exposition concludes with some guidelines for future research.

Produção e purificação de biogás utilizando microalga spirulina sp. LEB-18

O crescimento da população mundial e a tentativa de substituição parcial dos combustíveis fósseis por novas fontes de energia têm levado a uma maior atenção quanto à possível escassez de alimentos e a carência de grandes áreas disponíveis para agricultura. Microalgas, por meio do metabolismo fotossintético, utilizam energia solar e gás carbônico como nutrientes para o crescimento. A microalga Spirulina pode ser utilizada como suplemento alimentar, na biofixação de CO2, como fonte de biocombustíveis e no tratamento de efluentes. A digestão anaeróbia da biomassa microalgal produz biogás e os resíduos deste processo podem ser utilizados como substrato para novos cultivos da microalga. O objetivo deste trabalho foi estudar a conversão de Spirulina sp. LEB-18 em biogás em escala piloto e produzir biomassa microalgal utilizando os efluentes bicarbonato e dióxido de carbono do processo anaeróbio como fonte de nutrientes. Spirulina foi utilizada como substrato na digestão anaeróbia para produção de biogás em escala piloto sob temperaturas variáveis (12- 38 °C). Efluente do processo anaeróbio foi adicionado (20 %, v/v) como fonte de carbono no cultivo da microalga para avaliar o crescimento e a composição da biomassa. A seguir foi avaliada a capacidade da microalga de remover CO2 presente no biogás através de biofixação para obtenção do biocombustível purificado. O biogás produzido sob as diferentes temperaturas apresentou entre 72,2 e 74,4 % de CH4, quando realizado nas temperaturas 12 a 21 °C e 26 a 38 °C, respectivamente. A redução na temperatura do processo anaeróbio provocou um decréscimo na conversão de biomassa em biogás (0,30 para 0,22 g.g-1 ), ocorrendo dentro da faixa adequada e segura para as bactérias metanogênicas (pH 6,9; alcalinidade entre 1706,0 e 2248,0 mg.L-1 CaCO3 e nitrogênio amoniacal 479,3 a 661,7 mg.L-1 ). Os cultivos de Spirulina sp. LEB-18 em efluente anaeróbio contendo 20 % (v/v) e meio Zarrouk modificado (NaHCO3 2,8 e 5,3 g.L-1 ) apresentaram velocidade específica máxima de crescimento entre 0,324 e 0,354 d-1 , produtividade volumétrica entre 0,280 e 0,297 g.L-1 .d-1 e produtividade areal entre 14,00 e 14,85 g.m-2 .d-1 , sem diferenças significativas (p > 0,05) entre as diferentes condições estudadas. Lipídios variaram entre 4,9 e 5,0 % com proporção de ácido linoleico maximizada nos meios com efluente e ácido alfa-linolênico reduzida nesses meios em comparação ao meio Zarrouk completo. Nos ensaios para avaliar a capacidade da microalga Spirulina sp. LEB-18 de remover CO2 contaminante no biogás, as máximas concentrações celulares e produtividades de biomassa variaram, respectivamente, entre 1,12 e 1,24 g.L-1 e 0,11 e 0,14 g.L-1 .d-1 , não apresentando diferenças significativas (p > 0,05) entre os ensaios. A maior fixação diária total (FDT) de dióxido de carbono obtida foi 58,01 % (v/v) em cultivos com adição de biogás contendo 25 % (v/v) CO2. Obteve-se biogás com 89,5 % (v/v) de CH4 após injeção em cultivos de Spirulina, no qual aproximadamente 45 % (v/v) do CO2 injetado foi fixado pela microalga, gerando biomassa para diversas aplicações e biogás purificado.

Monitoramento por microcontrolador do cultivo de spirulina em fotobiorreator raceway

A oportunidade de produção de biomassa microalgal tem despertado interesse pelos diversos destinos que a mesma pode ter, seja na produção de bioenergia, como fonte de alimento ou servindo como produto da biofixação de dióxido de carbono. Em geral, a produção em larga escala de cianobactérias e microalgas é feita com acompanhamento através de análises físicoquímicas offline. Neste contexto, o objetivo deste trabalho foi monitorar a concentração celular em fotobiorreator raceway para produção de biomassa microalgal usando técnicas de aquisição digital de dados e controle de processos, pela aquisição de dados inline de iluminância, concentração de biomassa, temperatura e pH. Para tal fim foi necessário construir sensor baseado em software capaz de determinar a concentração de biomassa microalgal a partir de medidas ópticas de intensidade de radiação monocromática espalhada e desenvolver modelo matemático para a produção da biomassa microalgal no microcontrolador, utilizando algoritmo de computação natural no ajuste do modelo. Foi projetado, construído e testado durante cultivos de Spirulina sp. LEB 18, em escala piloto outdoor, um sistema autônomo de registro de informações advindas do cultivo. Foi testado um sensor de concentração de biomassa baseado na medição da radiação passante. Em uma segunda etapa foi concebido, construído e testado um sensor óptico de concentração de biomassa de Spirulina sp. LEB 18 baseado na medição da intensidade da radiação que sofre espalhamento pela suspensão da cianobactéria, em experimento no laboratório, sob condições controladas de luminosidade, temperatura e fluxo de suspensão de biomassa. A partir das medidas de espalhamento da radiação luminosa, foi construído um sistema de inferência neurofuzzy, que serve como um sensor por software da concentração de biomassa em cultivo. Por fim, a partir das concentrações de biomassa de cultivo, ao longo do tempo, foi prospectado o uso da plataforma Arduino na modelagem empírica da cinética de crescimento, usando a Equação de Verhulst. As medidas realizadas no sensor óptico baseado na medida da intensidade da radiação monocromática passante através da suspensão, usado em condições outdoor, apresentaram baixa correlação entre a concentração de biomassa e a radiação, mesmo para concentrações abaixo de 0,6 g/L. Quando da investigação do espalhamento óptico pela suspensão do cultivo, para os ângulos de 45º e 90º a radiação monocromática em 530 nm apresentou um comportamento linear crescente com a concentração, apresentando coeficiente de determinação, nos dois casos, 0,95. Foi possível construir um sensor de concentração de biomassa baseado em software, usando as informações combinadas de intensidade de radiação espalhada nos ângulos de 45º e 135º com coeficiente de determinação de 0,99. É factível realizar simultaneamente a determinação inline de variáveis do processo de cultivo de Spirulina e a modelagem cinética empírica do crescimento do micro-organismo através da equação de Verhulst, em microcontrolador Arduino.

CO2 utilization and alternative solvents: effective tools for sustainable applications

The growing concentration of CO2 in the atmosphere and its harmful consequences has led the scientific community to direct its efforts towards sustainable processes. Among the possible approaches, the use of CO2 and alternative solvents are two strategies that are having widespread diffusion. In this work the reuse of CO2 is expressed by using it as a reaction reagent and as trigger to change the physical properties of a catalyst thus facilitating its recovery. As regards the CO2 use as reagent, two catalytic systems have been developed for the conversion of CO2 and epoxides into cyclic carbonates, used in the synthesis of polymers and as aprotic solvents. Homogeneous catalysts made by choline-based eutectic mixtures and heterogeneous catalysts made from biopolymers and waste pyrolysis have been synthesized and tested on this reaction. The carbonate interchange reaction (CIR) of a diol with a linear carbonate (as dimethyl carbonate) is an interesting alternative, for the synthesis of cyclic carbonates; as the second application of CO2 as polarity trigger, it was used for catalyst recovery. In fact DBU, here used as catalyst, is part of the so called “switchable solvents”: they can pass from a less-polar to a more-polar form (and from being soluble to non-soluble in the reaction mixture) when reacting with CO2 in presence of water or alcohols. Also in this case, heterogeneous catalysts made from biopolymers and waste pyrolysis have been synthesized and tested on CIR. As for the use of alternative solvents, this work focuses on the use of Deep Eutectic Solvents (DESs). They are a new generation of solvents composed by a mixture of two or more substances, liquid at room temperature, and non-volatile. New and biobased DESs were here used: i) as reaction media to carry out chemoenzymatic epoxidation; ii) in the extraction of astaxanthin from microalgae culture.

Sustainability Evaluation of Biodiesel Produced from Microalgae Chlamydomonas sp Grown in Brewery Wastewater

This study performs a sustainability evaluation of biodiesel from microalga Chlamydomonas sp. grown in 20 % (v/v) of brewery’s wastewater, blended with pentose sugars (xylose, arabinose or ribose resulting from the hydrolysis of brewer’s spent grains (BSG). The life cycle steps considered for the study are: microalgae cultivation, biomass processing and lipids extraction at the brewery site, and its conversion to biodiesel at a dedicated external biofuel’s plant. Three sustainability indicators (LCEE, FER and GW) were considered and calculated using experimental data. Literature data was used, whenever necessary, to complement life cycle data, thus allowing a more accurate sustainability evaluation. A comparative analysis of the biodiesel life cycle steps was also conducted, with the main goal of identifying which steps need to be improved. Results show that biomass processing, especially cell harvesting, microalgae cultivation, and lipids extraction are the main process bottlenecks. It is also analysed the influence on the microalgae biodiesel sustainability of adding each pentose sugar to the cultivation media, concluding that it strongly influences the biomass and lipid productivity. In particular, the addition of xylose is preferable in terms of lipid productivity, but from a sustainability point of view, ribose is the best, though the difference from xylose is not significant. Nevertheless, culture without pentose addition presents the best sustainability results.

Cultivation of microalgae Spirulina platensis (Arthrospira platensis) from biological treatment of swine wastewater

The microalgae biomass production from swine wastewater is a possible solution for the environmental impact generated by wastewater discharge into water sources. The biomass can be added to fish feed, which can be used in the formulation of meat products. This work addresses the adaptation of the microalgae Spirulina platensis (Arthrospira platensis) in swine wastewater and the study of the best dilution of the wastewater for maximum biomass production and for removal of Chemical Oxygen Demand (COD), ammonia and phosphorous to the microalgae. The cultivation of Spirulina platensis, strain Paracas presented maximum cellular concentrations and maximum specific growth rates in the wastewater concentration of 5.0 and 8.5%. The highest COD removals occurred with 26.5 and 30.0% of wastewater in the medium. The maximum removal of total phosphorous (41.6%), was with 8.5% of wastewater, which is related to the microalgae growth. The results of Spirulina culture in the swine wastewater demonstrated the possibility of using these microalgae for the COD and phosphorous removal and for biomass production.

Estimating microalgae Synechococcus nidulans daily biomass concentration using neuro-fuzzy network

In this study, a neuro-fuzzy estimator was developed for the estimation of biomass concentration of the microalgae Synechococcus nidulans from initial batch concentrations, aiming to predict daily productivity. Nine replica experiments were performed. The growth was monitored daily through the culture medium optic density and kept constant up to the end of the exponential phase. The network training followed a full 3³ factorial design, in which the factors were the number of days in the entry vector (3,5 and 7 days), number of clusters (10, 30 and 50 clusters) and internal weight softening parameter (Sigma) (0.30, 0.45 and 0.60). These factors were confronted with the sum of the quadratic error in the validations. The validations had 24 (A) and 18 (B) days of culture growth. The validations demonstrated that in long-term experiments (Validation A) the use of a few clusters and high Sigma is necessary. However, in short-term experiments (Validation B), Sigma did not influence the result. The optimum point occurred within 3 days in the entry vector, 10 clusters and 0.60 Sigma and the mean determination coefficient was 0.95. The neuro-fuzzy estimator proved a credible alternative to predict the microalgae growth.

Isolation and identification of native microalgae for biodiesel production

La demande croissante en carburants, ainsi que les changements climatiques dus au réchauffement planétaire poussent le monde entier à chercher des sources d’énergie capables de produire des combustibles alternatifs aux combustibles fossiles. Durant les dernières années, plusieurs sources potentielles ont été identifiées, les premières à être considérées sont les plantes oléagineuses comme source de biocarburant, cependant l’utilisation de végétaux ou d’huiles végétales ayant un lien avec l’alimentation humaine peut engendrer une hausse des prix des denrées alimentaires, sans oublier les questions éthiques qui s’imposent. De plus, l'usage des huiles non comestibles comme sources de biocarburants, comme l’huile de jatropha, de graines de tabac ou de jojoba, révèle un problème de manque de terre arable ce qui oblige à réduire les terres cultivables de l'industrie agricole et alimentaire au profit des cultures non comestibles. Dans ce contexte, l'utilisation de microorganismes aquatiques, tels que les microalgues comme substrats pour la production de biocarburant semble être une meilleure solution. Les microalgues sont faciles à cultiver et peuvent croitre avec peu ou pas d'entretien. Elles peuvent ainsi se développer dans des eaux douces, saumâtres ou salées de même que dans les terres non cultivables. Le rendement en lipide peut être largement supérieur aux autres sources de biocarburant potentiel, sans oublier qu’elles ne sont pas comestibles et sans aucun impact sur l'industrie alimentaire. De plus, la culture intensive de microalgues pour la production de biodiesel pourrait également jouer un rôle important dans l'atténuation des émissions de CO2. Dans le cache de ce travail, nous avons isolé et identifié morphologiquement des espèces de microalgues natives du Québec, pour ensuite examiner et mesurer leur potentiel de production de lipides (biodiesel). L’échantillonnage fut réalisé dans trois régions différentes du Québec: la région de Montréal, la gaspésie et le nord du Québec, et dans des eaux douces, saumâtres ou salées. Cent souches ont été isolées à partir de la région de Montréal, caractérisées et sélectionnées selon la teneur en lipides et leur élimination des nutriments dans les eaux usées à des températures différentes (10 ± 2°C et 22 ± 2°C). Les espèces ayant une production potentiellement élevée en lipides ont été sélectionnées. L’utilisation des eaux usées, comme milieu de culture, diminue le coût de production du biocarburant et sert en même temps d'outil pour le traitement des eaux usées. Nous avons comparé la biomasse et le rendement en lipides des souches cultivées dans une eau usée par apport à ceux dans un milieu synthétique, pour finalement identifié un certain nombre d'isolats ayant montré une bonne croissance à 10°C, voir une teneur élevée en lipides (allant de 20% à 45% du poids sec) ou une grande capacité d'élimination de nutriment (>97% d'élimination). De plus, nous avons caractérisé l'une des souches intéressantes ayant montré une production en lipides et une biomasse élevée, soit la microalgue Chlorella sp. PCH90. Isolée au Québec, sa phylogénie moléculaire a été établie et les études sur la production de lipides en fonction de la concentration initiale de nitrate, phosphate et chlorure de sodium ont été réalisées en utilisant de la méthodologie des surfaces de réponse. Dans les conditions appropriées, cette microalgue pourrait produire jusqu'à 36% de lipides et croitre à la fois dans un milieu synthétique et un milieu issu d'un flux secondaire de traitement des eaux usées, et cela à 22°C ou 10°C. Ainsi, on peut conclure que cette souche est prometteuse pour poursuivre le développement en tant que productrice potentielle de biocarburants dans des conditions climatiques locales.