Browsing by Subject "Microalgae"

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    Approach to biodiesel production from microalgae under supercritical conditions by the PRISMA method
    (Elsevier, 2019) Ortiz Martínez, Víctor Manuel; Andreo Martínez, Pedro; García Martínez, Nuria; Pérez de los Ríos, Antonia; Hernández Fernández, Francisco José; Quesada Medina, Joaquín; Química Agrícola, Geología y Edafología
    Increasing energy demands lead to the search for sustainable biofuels such as biodiesel from renewable sources such as algal biomass. Specially, microalgae have become increasingly popular as biodiesel feedstock due to their fast-growing rates and relatively high level of lipids. The non-catalytic transesterification reaction of microalgae oil under supercritical conditions in the presence of alcohols is an efficient process for biodiesel production and can overcome some of the limitations posed by subcritical catalytic transesterification. Two-step and one-step processes have been reported for this purpose, in the last case with extraction and transesterification stages being performed simultaneously. This works offer a systematic review using the PRISMA methodology analyzing the status of this research topic and identifying future research strategies. With this work, PRISMA methodology is applied for the first time within technological engineering fields. Moreover, this is the first specific overview on the production of biodiesel from microalgae under supercritical conditions. Several key factors such as microalgae type and operation variables including extraction oil, temperature and reaction time, pressure, water content in biomass, alcohol excess and final biodiesel properties are discussed. Further efforts need to be done in order to study the continuous biodiesel production by the development of integrated processes that involve both microalgae cultivation and biodiesel production.
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    Cellular responses to electromagnetic fields and ultraviolet radiation: an in vitro study on microalgae and fish cell lines
    (Elsevier, 2026) Ortiz García, María; Terrer Marcilla de Teruel Moctezuma, José María; García Gamuz, José Antonio; Esteban Abad, María de los Ángeles; Aboal Sanjurjo, Marina; Biología Celular e Histología; María Ángeles Esteban Abad; Facultades de la UMU::Facultad de Biología
    Background The molecular effects involved in the cellular response to non-ioninzing electromagnetic radiation on marine and freshwater microalgae and fish cell lines are incompletely understood. Objectives The direct impact of non-ionizing electromagnetic radiation on marine and freshwater microalgae and fish cell lines was investigated. Methods Six microalgae species from different taxonomic groups were exposed to extremely low-frequency electromagnetic fields (ELF-EMF) for five days. Four fish cell lines (SAF-1, DLB-1, DLEC, and Fugu eye) were exposed to ultraviolet (UV) radiation, with SAF-1 demonstrating the highest sensitivity. In addition, three commercial antioxidants (2101, 3600, and 4004) were tested for their possible radioprotective effects. Results Although no statistically significant differences in cell density were observed, certain taxa (Chlorotylium sp., Mayamea sp., and Scenedesmus sp.) exhibited a declining trend compared to the controls, suggesting species-specific sensitivity to ELF-EMF. Principal component analysis revealed significant differences in physiological responses, particularly in photosynthetic variables such as electron transport rate and dissolved carbon. The total antioxidant capacity did not differ significantly between the control and exposed microalgae, and Chlorotylium sp. showed the highest basal levels. The photosystem II productivity index remained largely unaffected by ELF-EMF exposure, except for an increase in irradiated Scenedesmus sp. Low antioxidant concentrations (≤125 µg/ml) and short incubation times (6 h) of 2101 and 3600 induced proliferation or increased cell viability, particularly under irradiation. However, prolonged incubation time (24 h) or high antioxidant concentrations (≥250 µg/ml) resulted in significant cytotoxicity in all cell lines.
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    Effects of living cyanobacteria, cyanobacterial extracts and pure microcystins on growth and ultrastructure of microalgae and bacteria
    (Elsevier, 2006-12-02) Aboal Sanjurjo, Marina; Valdor Alonso, Rut; Bioquímica y Biología Molecular B e Inmunología
    In this study, we demonstrate the inhibitory effect of both cyanobacterial extracts and pure microcystins on the growth of microalgae and bacteria. This inhibitory effect was more persistent in pure microcystins than in the extracts, which lost their properties eight days after exposure. In addition, the effects on bacteria were longerlasting than those on microalgae. The microalgae exposed to both extracts and cultures of microcystin producing species showed morphological and ultrastructural alterations, even in cases where there was no clear effect on growth. The implications for colonisation and benthic communities structure and development are discussed in the context of biomonitoring.
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    Modelling of photosynthesis, respiration and nutrients yield coefficients in Scenedemus almeriensis culture as a function of nitrogen and phosphorus.
    (2021-09-14) Gómez serrano, Cintia; Acién Fernández, Francisco Gabriel; Fernández Sevilla, José María; Molina Grima, Emilio; Sánchez Zurano, Ana; Ingeniería Química
    Se aplicaron técnicas foto-respirométricas para evaluar la actividad fotosintética en organismos fototróficos. Estos métodos permiten analizar la respuesta fotosintética bajo diferentes condiciones. En este trabajo, se estudió la influencia de la disponibilidad de nutrientes (nitrato, amonio y fosfato) en la fotosíntesis y la respiración de Scenedesmus almeriensis mediante mediciones foto-respirométricas cortas. Tanto la fotosíntesis como la respiración aumentaron hasta un valor de saturación y posteriormente disminuyeron, mostrando inhibición a concentraciones altas. En cuanto a la influencia de la concentración de fósforo en las células de microalgas, se observó una tendencia hiperbólica similar, aunque no se detectó inhibición a concentraciones elevadas. A partir de estos datos experimentales, las tasas de respiración y fotosíntesis de S. almeriensis se modelaron utilizando la ecuación de Haldane para los datos de nitrato y amonio, y la ecuación de Monod para los datos de fosfato. Además, se realizaron experimentos para determinar los coeficientes de rendimiento de nitrógeno y fósforo en los cultivos de S. almeriensis. Los resultados mostraron que estos coeficientes no son constantes y se modifican según la concentración de nutrientes, evidenciando el fenómeno de absorción de lujo. Finalmente, los modelos propuestos se incorporaron en una herramienta de simulación para evaluar la actividad fotosintética y los coeficientes de rendimiento de nutrientes de S. almeriensis cuando se utilizan diferentes medios de cultivo y aguas residuales como fuente de nitrógeno y fósforo para su crecimiento.