Effects of CO2 enrichment on microstructure and ultrastructure of two species of freshwater green algae

order to investigate the morphological response of freshwater green algae to elevated CO2 concentration, Chlamydomonas reinhardtii Dang and Scenedesmus obliquus Kutz were cultured with enriched CO2, and their microstructure and ultrastructure were examined by microscopy and electron microscopy. The effect of CO2 enrichment to 186 mumol/L, was insignificant on the shape and size of C. reinhardtii, but significant in reducing the volume of S. obliquus. High-CO2 increased the amount of chloroplast. The pyrenoids occurred in low-CO2-grown cells but not in high-CO2-grown ones and more starch granules were observed in the former.

Life history characteristics of three types of females in Brachionus calyciflorus Pallas (Rotifera) fed different algae

This study describes the life history characteristics of amictic, unfertilized mictic and fertilized mictic females of the rotifer Brachionus calyciflorus cultured individually on two different algae at 0.1 mg ml(-1) food concentration and 27 degreesC. The duration of the juvenile period of amictic females was significantly shorter on Chlorella pyrenoidosa Chick than on Scenedesmus obliquus Kutz or both algae together. The duration of the juvenile period of unfertilized mictic females was significantly longer, and the number of eggs produced by amictic females was significantly larger on Chlorella pyrenoidosa than on S. obliquus. When fed the same type of alga, the duration of the juvenile period of the fertilized mictic females was the longest among the three types of females, and the durations of the reproductive period of the amictic females and the post-reproductive period of the fertilized mictic females were longer than, or equal to those of the other two types of females, respectively. The number of eggs produced by an unfertilized mictic female was the largest among the three types of females, and that of amictic females was larger than or equal to that of fertilized mictic females, depending on the type of diet.

The effect of food concentration on the life history of three types of Brachionus calyciflorus females

The effect of food concentration on the life history of three types of Brachionus calciflorus females (amictic, unfertilized mictic and fertilized mictic female) was studied with replicated individual cultures at 25 degrees and at four food concentrations (1.5, 3.0, 6.0 and 9.0 x 10(6) cells mL(-1)) of Scenedesmus obliquus. There were highly significant effects of both food concentration and female type, independently and in interaction on the duration of juvenile period of the rotifer, but neither a;ere the effects on the duration of post-reproductive period and mean life-span. The duration of juvenile period of unfertilized mictic female at the food concentration of 9.0 x 10(6) cells mL(-1) was the longest among all the food concentration-female type combinations. Both food concentration and female type influenced significantly the duration of reproductive period and the number of eggs produced by each type of female per life cycle, respectively. There was, however, no significant interaction between food level and female type. Among the three types of females, the number of eggs produced by an unfertilized mictic female was the largest. and that of a fertilized mictic female was the smallest.

The impacts of replacing air bubbles with microspheres for the clarification of algae from low cell-density culture

Dissolved Air Flotation (DAF) is a well-known coagulation-flotation system applied at large scale for microalgae harvesting. Compared to conventional harvesting technologies DAF allows high cell recovery at lower energy demand. By replacing microbubbles with microspheres, the innovative Ballasted Dissolved Air Flotation (BDAF) technique has been reported to achieve the same algae cell removal efficiency, while saving up to 80% of the energy required for the conventional DAF unit. Using three different algae cultures (Scenedesmus obliquus, Chlorella vulgaris and Arthrospira maxima), the present work investigated the practical, economic and environmental advantages of the BDAF system compared to the DAF system. 99% cells separation was achieved with both systems, nevertheless, the BDAF technology allowed up to 95% coagulant reduction depending on the algae species and the pH conditions adopted. In terms of floc structure and strength, the inclusion of microspheres in the algae floc generated a looser aggregate, showing a more compact structure within single cell alga, than large and filamentous cells. Overall, BDAF appeared to be a more reliable and sustainable harvesting system than DAF, as it allowed equal cells recovery reducing energy inputs, coagulant demand and carbon emissions. © 2014 Elsevier Ltd.

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.

Food and fuel microalgae applications: insights from portuguese experience [Resumo]

Microalgae have a wide range of application fields, from food to fuels, to pharmaceuticals & fine chemicals, aquaculture and environmental bioremediation, among others. Spirulina and Chlorella have been used as food sources since ancient times, due to their high and balanced nutritional value. Our research group in Lisbon has developed a range of food products (emulsions, gelled desserts, biscuits and pastas) enriched with freshwater and marine microalgae (Spirulina, Chlorella, Haematococcus, Isochrysis and Diacronema). The developed products presented attractive and stable colours, high resistance to oxidation and enhanced rheological properties. Some of these products will be prepared at the Post-Congress Course “Functional Foods Development” at the University of Antofagasta. More recently, a great interest has arisen on using microalgae for biofuel production. The same group has also been exploring several marine and freshwater species for biofuel production (e.g., biodiesel, bioethanol, biohydrogen and biomethane) within a biorefinery approach, in order to obtain high and low-value co-products using integral biomass maximizing the energy revenue. Namely, supercritical fluid extraction of Nannochloropsis sp. allowed the recovery of valuable carotenoids and lipids, prior to bioH2 production through dark fermentation of the residual biomass. Also, Scenedesmus obliquus residues after sugars (for bioethanol) and lipids (for biodiesel) extraction has been anaerobically digested attaining high biomethane yields. Regarding sustainability issues, the current trend of our group is now focused on using liquid effluents and high CO2 levels for low cost microalgae growth, contributing to a lower water demand, primary energy consumption and global warming potential by reducing the need for potable water and fertilizers (P, N) and increasing CO2 mitigation. Microalgae biomass has been successfully used for urban wastewater treatment with subsequent bioH2 production, in a biorefinery approach. Presently, ammonium-rich raw effluents from piggeries and poultry industry are being effectively used for microalgae growth avoiding any pre-treatment step.

Produção e extração da enzima anidrase carbônica e de ficobiliproteínas a partir de microalgas

Muito interesse tem sido focado no potencial biotecnológico das microalgas, principalmente devido à identificação de diversas substâncias sintetizadas por estes organismos, dentre elas a anidrase carbônica e as ficobiliproteínas. A anidrase carbônica é uma metaloenzima que catalisa a hidratação reversível do CO2 em bicarbonato com alta eficiência, sendo utilizada para captação de CO2 através de sistemas biológicos. A C-ficocianina e a aloficocianina, corantes naturais, são os dois principais componentes das ficobiliproteínas em cianobactérias e apresentam diversas aplicações dentro da indústria alimentícia, cosmética e farmacêutica. O objetivo principal desta tese foi avaliar a produção e a extração da anidrase carbônica e das ficobiliproteínas a partir de diferentes microalgas. Para isso, primeiramente foi realizado uma investigação da produção da anidrase carbônica pela microalga Dunaliella tertiolecta, onde foi estudada a extração da enzima e sua aplicação em sistemas de captura enzimática de CO2. Posteriormente foi avaliada a produção da enzima ao longo do cultivo de diferentes microalgas marinhas e dulcícolas (Dunaliella tertiolecta, Tetraselmis sueccica, Phaeodactylum tricornutum, Nannochloropsis oculata, Isochysis galbana, Chlorella vulgaris e Scenedesmus obliquus). A produção da enzima e de ficobiliproteínas, também, foi estudada para as cianobactérias Spirulina platensis LEB 52, Spirulina sp. LEB 18 e Synechococcus nidulans. Todos os cultivos foram acompanhados em termos de biomassa e pH. Por último, foi realizado um estudo de extração da enzima de P. tricornutum e extração conjunta da anidrase carbônica e de ficobiliproteínas da cianobactéria S. sp. LEB 18. Os cultivos foram realizados em frascos erlenmeyer contendo os meios Conway (marinhas), BG-11 (dulcícolas) e Zarrouk 20% (cianobactérias). Na avaliação da ruptura celular foram testadas as técnicas de maceração em gral e pistilo, agitação em vórtex com pérolas de vidro, sonicação com pérolas de vidro, homogeneizador ultrassônico, secagem, congelamento e descongelamento e a combinação de tratamentos. Maiores rendimentos de extração da enzima a partir da microalga D. tertiolecta foram obtidos utilizando tratamento ultrassônico, juntamente com baixas concentrações de biomassa úmida (0,1 e 0,2 g/L), e a mesma apresentou potencial para aplicação em processos de captação enzimática do CO2. Durante os cultivos, a microalga C. vulgaris se destacou como maior produtora da enzima anidrase carbônica, atingindo valores de atividade enzimática de 44,0 U/L. As cianobactérias apresentaram valores de atividade entre 41,6 e 45,9 U/L, sendo que a S. sp. LEB 18 foi a que apresentou maiores produções de C-ficocianina e aloficocianina no ponto de máxima atividade volumétrica, 65,9 e 82,2 µg/mL, respectivamente. A enzima extraída da biomassa de S. platensis LEB 52 catalisou a hidratação do CO2 que precipitou na forma de CaCO3. Maiores rendimentos de extração da enzima a partir das microalgas P. tricornutum e S. sp. LEB 18 foram obtidos utilizando homogeneizador ultrassônico, que foram 31,3 U/g e 25,5 U/g, respectivamente. A biomassa de S. sp. LEB 18, também apresentou potencial para a extração de ficobiliproteínas, obtendo- se altas concentrações de C-ficocianina (100,5 mg/g) e aloficocianina (69,9 mg/g). Através dos resultados obtidos, pode-se verificar a potencialidade das microalgas e das cianobactérias para produção da enzima anidrase carbônica e das ficobiliproteínas, biomoléculas de alto valor industrial. Este trabalho apresenta processos eficientes para a extração da enzima e de ficobiliproteínas tanto para escala laboratorial como industrial.

Production de biodiesel à partir de microalgues par catalyses homogène et hétérogène

Résumé : Au Canada, près de 80% des émissions totales, soit 692 Mt eq. CO[indice inférieur 2], des gaz à effet de serre (GES) sont produits par les émissions de dioxyde de carbone (CO[indice inférieur 2]) provenant de l’utilisation de matières fossiles non renouvelables. Après la Conférence des Nations Unies sur les changements climatiques, COP21 (Paris, France), plusieurs pays ont pour objectif de réduire leurs émissions de GES. Dans cette optique, les microalgues pourraient être utilisées pour capter le CO[indice inférieur 2] industriel et le transformer en biomasse composée principalement de lipides, de glucides et de protéines. De plus, la culture des microalgues n’utilise pas de terre arable contrairement à plusieurs plantes oléagineuses destinées à la production de biocarburants. Bien que les microalgues puissent être transformées en plusieurs biocarburants tels le bioéthanol (notamment par fermentation des glucides) ou le biométhane (par digestion anaérobie), la transformation des lipides en biodiesel pourrait permettre de réduire la consommation de diesel produit à partir de pétrole. Cependant, les coûts reliés à la production de biodiesel à partir de microalgues demeurent élevés pour une commercialisation à court terme en partie parce que les microalgues sont cultivées en phase aqueuse contrairement à plusieurs plantes oléagineuses, ce qui augmente le coût de récolte de la biomasse et de l’extraction des lipides. Malgré le fait que plusieurs techniques de récupération des lipides des microalgues n’utilisant pas de solvant organique sont mentionnées dans la littérature scientifique, la plupart des méthodes testées en laboratoire utilisent généralement des solvants organiques. Les lipides extraits peuvent être transestérifiés en biodiesel en présence d’un alcool tel que le méthanol et d’un catalyseur (catalyses homogène ou hétérogène). Pour la commercialisation du biodiesel à partir de microalgues, le respect des normes ASTM en vigueur est un point essentiel. Lors des essais en laboratoire, il a été démontré que l’extraction des lipides en phase aqueuse était possible afin d’obtenir un rendement maximal en lipides de 36% (m/m, base sèche) en utilisant un prétraitement consistant en une ébullition de la phase aqueuse contenant les microalgues et une extraction par des solvants organiques. Pour l’estérification, en utilisant une résine échangeuse de cations (Amberlyst-15), une conversion des acides gras libres de 84% a été obtenue à partir des lipides de la microalgue Chlorella protothecoïdes dans les conditions suivantes : température : 120°C, pression autogène, temps de réaction : 60 min, ratio méthanol/lipides: 0.57 mL/g et 2.5% (m/m) Amberlyst-15 par rapport aux lipides. En utilisant ces conditions avec une catalyse homogène (acide sulfurique) et une seconde étape alcaline avec de l’hydroxyde de potassium (température : 60°C ; temps de réaction : 22.2 min; ratio catalyseur microalgue : 2.48% (m/m); ratio méthanol par rapport aux lipides des microalgues : 31.4%), un rendement en esters méthyliques d’acides gras (EMAG) de 33% (g EMAG/g lipides) a été obtenu à partir des lipides de la microalgue Scenedesmus Obliquus. Les résultats démontrent que du biodiesel peut être produit à partir de microalgues. Cependant, basé sur les présents résultats, il sera necessaire de mener d’autre recherche pour prouver que les microalgues sont une matière première d’avenir pour la production de biodiesel.

Interações do lantânio e cério com microalgas dos gêneros Monoraphidium e Scenedesmus

Os elementos de terras raras, representados em sua maioria pelos lantanídeos, ocorrem principalmente como constituintes-traço da maioria dos minerais de rochas comuns (monazita, apatita) e também estão presentes em alguns minérios. Tais elementos foram largamente usados por décadas como fertilizantes na China. Na área das inovações tecnológicas, a demanda por esses metais vem crescendo por conta das suas aplicações em diversos campos. Consequentemente, grandes quantidades desses elementos são acumulados em ambientes aquáticos atingindo o fitoplâncton. Assim, as microalgas que são organismos ecologicamente importantes na cadeia alimentar têm sido frequentemente usadas em estudos ambientais para avaliar a toxicidade relativa de várias descargas químicas e são largamente estudadas na detecção dos primeiros impactos no ecossistema. Somado a isso, são biomassas que possuem boa capacidade de biossorção de metais devido à presença de ligantes na sua estrutura que promovem a captação deles quando em solução. Dessa forma, as interações entre as microalgas verdes Monoraphidium e Scenedesmus e os íons La3+ e Ce3+ foram investigadas neste trabalho. Para isso, foram avaliados o efeito tóxico e a bioacumulação do La3+ pelas duas microalgas verdes. Adicionalmente, estudos em batelada da biossorção do La3+ e Ce3+ em soluções contendo os elementos isoladamente ou em combinação foram realizados. No estudo de toxicidade e de bioacumulação o meio de cultivo utilizado foi o ASM-1, com e sem presença de La3+ (10 mg.L-1 a 100 mg.L-1), onde o efeito tóxico do metal foi monitorado por análises micro e macroscópica das células e também pela quantificação do crescimento celular baseada em medidas da massa seca. A bioacumulação do metal foi avaliada da mesma forma para ambas as microalgas. Os resultados obtidos mostraram que o efeito tóxico do metal foi presente em concentrações iônicas de 50 e 100 mg.L-1 e que houve uma bioconcentração do La3+ em ambas espécies de microalgas, principalmente quando a concentração inicial do La3+ foi de 10 e 25 mg.L-1, mostrando que houve uma relação direta entre a bioconcentração e a toxicidade do La3+. O gênero Monoraphidium bioconcentrou mais metal que o gênero Scenedesmus. Os resultados da biossorção dos metais em solução monoelementar mostraram que as microalgas apresentaram grande capacidade de captação do La3+ (20,7 mmol.g-1 para Monoraphidium sp. e 17,8 mmol.g-1 para Scenedesmus sp.) e do Ce3+ (25,7 mmol.g-1 para Monoraphidium sp. e 11,5 mmol.g-1 para Scenedesmus sp.). Os resultados obtidos revelaram que os dados melhor se ajustaram ao modelo de Freundlich, na maioria dos casos. Em sistema binário, notou-se que houve uma menor captação de cada um individualmente, evidenciando uma competição entre eles pelos mesmos sítios ligantes e que ambas apresentaram maior afinidade pelo Ce3+

极高CO_2胁迫对被甲栅藻(Scenedesmus armatus)生理活性和细胞结构影响

以被甲栅藻(Scenedesmusarmatus)为材料研究极高浓度CO2对其生理活性和细胞结构的影响。研究表明,被甲栅藻能在60%的CO2浓度下快速生长,在5%、20%、40%、60%、80%、100%CO2浓度下的平均增长率分别是1.228、0.925、0.741、0.305、0.042、0.001g·L-1·d-1DW。通入极高浓度CO2(20%、40%)后,被甲栅藻细胞的光系统II(PSII)最大光化学效率(Fv/Fm)在24h内明显下降,对PSII抑制作用较明显;其后,随培养时间的增长而逐渐恢复

光照强度对于斜生栅藻Scenedsmus obliquus(Turp.)K tz.生长的影响

<正> 浮游藻类的生长发育,和其它绿色植物一样,与光有密切的关系,因为光直接影响到它的光合作用的进行。在适度的光强度下,光的强度和植物的生长率是成正比的。这方面曾有过不少的工作。但是,在各种光强度的条件下,浮游藻类的数量,细胞分裂率和生物量的关系,却知道得不多。因此,在我们进行大量繁殖浮游藻类的试验时,做了一些关于光强度对于浮游藻类生长影响的试验,同时对于它的数量,细胞分裂率和生物量的关系上,看到了一些事实,现将初步的结

Different tolerances and responses to low temperature and darkness between waterbloom forming cyanobacterium Microcystis and a green alga Scenedesmus

The dynamics of planktonic cyanobacteria in eutrophicated freshwaters play an important role in formation of annual summer blooms, yet overwintering mechanisms of these water bloom forming cyanobacteria remain unknown. The responses to darkness and low temperature of three strains (unicellular Microcystis aeruginosa FACHB-905, colonial M. aeruginosa FACHB-938, and a green alga Scenedesmus quadricauda FACHB-45) were investigated in the present study. After a 30-day incubation under darkness and low temperature, cell morphology, cell numbers, chlorophyll a, photosynthetic activity (ETRmax and I-k), and malodialdehyde (MDA) content exhibited significant changes in Scenedesmus. In contrast, Microcystis aeruginosa cells did not change markedly in morphology, chlorophyll a, photosynthetic activity, and MDA content. The stress caused by low temperature and darkness resulted in an increase of the antioxidative enzyme-catalase (CAT) in all three strains. When the three strains re-grew under routine cultivated condition subjected to darkness and low temperature, specific growth rate of Scenedesmus was lower than that of Microcystis. Flow cytometry (FCM) examination indicated that two distinct types of metabolic response to darkness and low temperature existed in the three strains. The results from the present study reveal that the cyanobacterium Microcystis, especially colonial Microcystis, has greater endurance and adaptation ability to the stress of darkness and low temperature than the green alga Scenedesmus.

Changes in culture growth dynamics and cell size in a Scenedesmus quadricauda upon action of potassium dichromate

The effect of potassium dichromate in concentrations of 0.5 to 10 mg/l on a laboratory culture of Sc. quadricauda algae was studied in standard conditions. The total cell numbers decreased at potassium dichromate concentrations over 1 mg/l, and the proportion of living cells decreased at all studied concentrations. A positive correlation was found between changes in cell size and their numbers at toxin concentrations of 1 and 3 mg/l, and a negative correlation was found between the relative size and the cell numbers at 3 and 10 mg/l. This may be due to different intensity of growth inhibition and cell division under the influence of the toxin. The culture sensitivity to the toxin increased in autumn and decreased in the spring.

FATE OF 2 PHENYLBENZOYLUREA INSECTICIDES IN AN ALGAE CULTURE SYSTEM (SCENEDESMUS-SUBSPICATUS)

The bioaccumulation, elimination and degradation of C-14-labelled diflubenzuron (DFB) and of 1-(2-chlorobenzoyl)-3-(4-chlorophenyl)urea (CCU) was studied in a laboratory algae culture system of scenedesmus subspicatus. Algae were exposed at an initial concentration of 200 mug/l for seven days. Neither substance had an inhibitory effect on the growth of algae. The half life of DFB and CCU was 3 and 1 days, respectively, as measured by HPLC. The distribution of C-14 between medium and algae was measured. In the case of DFB radioactivity in algae increased steadily and levelled off at approximately 60 % after 5 days. Due to algae growth BCF values decreased from 4310 to 889 for DFB and from 6719 to 304 for CCU during the exposure period. The relationship between algae density and bioconcentration could be correlated by an adsorption isotherm. Elimination of both compounds was rapid during the first hours.