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ABSTRACT: The influence of different parameters such as temperature, irradiance, nitrate concentration, pH, and an external carbon source on Synechocystis PCC 6803 growth was evaluated.
4.5-ml cuvettes containing 2 ml of culture, a high-throughput system equivalent to batch cultures, were used with gas exchange ensured by the use of a Parafilm™ cover. The effect of the different variables on maximum growth was assessed by a multi-way statistical analysis.
Temperature and pH were identified as the key factors. It was observed that Synechocystis cells have a strong influence on the external pH. The optimal growth temperature was 33°C while light-saturating conditions were reached at 40 µE·m⁻²·s⁻¹.
It was demonstrated that Synechocystis exhibits a marked difference in behavior between autotrophic and glucose-based mixotrophic conditions, and that nitrate concentrations did not have a significant influence, probably due to endogenous nitrogen reserves. Furthermore, a dynamic metabolic model of Synechocystis photosynthesis was developed to gain insights on the underlying mechanism enabling this cyanobacterium to control the levels of external pH. The model showed a coupled effect between the increase of the pH and ATP production which in turn allows a higher carbon fixation rate.
Journal of Molecular Microbiology and Biotechnology 04/2012; 22(2):71-82. · 1.95 Impact Factor
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ABSTRACT: This article addresses the influence of anisotropy of the ground on steady-state temperature in the surroundings of vertical borehole and effective thermal conductivity measured by a field thermal response test. This is a key parameter in the design of ground coupled heat pumps to heat and cool buildings. First, this article provides a brief overview of the current technique of estimating thermal conductivity from data obtained in a thermal response test based on predictions for temperature from a line source of heat in an isotropic ground. Then, the analytical solutions to the isotropic model for the ground are used to obtain the solutions to the anisotropic model for stratified medium. In addition, the article provides a new analytical exact solution for temperatures around a finite line source of heat penetrating anisotropic semi-infinite medium, inwhich the angle between the ground surface and the sedimentary strata is arbitrary. Approximate expressions for the temperature evolution during the test and for the steady-state temperature are presented. Such approximate expressions are also given for integral mean temperature for two special orientations of the strata. The limitations of the finite line source method in stratified medium and recommendations for layout of multiple vertical or horizontal ground coupled heat exchangers or waste canisters in repository rock are discussed.
HVAC&R RESEARCH 12/2011; 17(6):1030-1046. · 0.68 Impact Factor
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Cristina Vilanova,
Angeles Hueso,
Carles Palanca,
Guillem Marco,
Miguel Pitarch,
Eduardo Otero,
Juny Crespo,
Jerzy Szablowski,
Sara Rivera,
Laura Domínguez-Escribà,
Emilio Navarro,
Arnau Montagud, Pedro Fernández de Córdoba,
Asier González,
Joaquín Ariño,
Andrés Moya,
Javier Urchueguía,
Manuel Porcar
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ABSTRACT: In this study, we show the use of direct external electrical stimulation of a jellyfish luminescent calcium-activated protein, aequorin, expressed in a transgenic yeast strain. Yeast cultures were electrically stimulated through two electrodes coupled to a standard power generator. Even low (1.5 V) electric pulses triggered a rapid light peak and serial light pulses were obtained after electric pulses were applied periodically, suggesting that the system is re-enacted after a short refraction time. These results open up a new scenario, in the very interphase between synthetic biology and cybernetics, in which complex cellular behavior might be subjected to electrical control.
Journal of biotechnology 02/2011; 152(3):93-5. · 2.88 Impact Factor
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ABSTRACT: Synechocystis sp. PCC6803 is a model cyanobacterium capable of producing biofuels with CO(2) as carbon source and with its metabolism fueled by light, for which it stands as a potential production platform of socio-economic importance. Compilation and characterization of Synechocystis genome-scale metabolic model is a pre-requisite toward achieving a proficient photosynthetic cell factory. To this end, we report iSyn811, an upgraded genome-scale metabolic model of Synechocystis sp. PCC6803 consisting of 956 reactions and accounting for 811 genes. To gain insights into the interplay between flux activities and metabolic physiology, flux coupling analysis was performed for iSyn811 under four different growth conditions, viz., autotrophy, mixotrophy, heterotrophy, and light-activated heterotrophy (LH). Initial steps of carbon acquisition and catabolism formed the versatile center of the flux coupling networks, surrounded by a stable core of pathways leading to biomass building blocks. This analysis identified potential bottlenecks for hydrogen and ethanol production. Integration of transcriptomic data with the Synechocystis flux coupling networks lead to identification of reporter flux coupling pairs and reporter flux coupling groups - regulatory hot spots during metabolic shifts triggered by the availability of light. Overall, flux coupling analysis provided insight into the structural organization of Synechocystis sp. PCC6803 metabolic network toward designing of a photosynthesis-based production platform.
Biotechnology Journal 01/2011; 6(3):330-42.
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ABSTRACT: Synechocystis sp. PCC6803 is a cyanobacterium considered as a candidate photo-biological production platform--an attractive cell factory capable of using CO2 and light as carbon and energy source, respectively. In order to enable efficient use of metabolic potential of Synechocystis sp. PCC6803, it is of importance to develop tools for uncovering stoichiometric and regulatory principles in the Synechocystis metabolic network.
We report the most comprehensive metabolic model of Synechocystis sp. PCC6803 available, iSyn669, which includes 882 reactions, associated with 669 genes, and 790 metabolites. The model includes a detailed biomass equation which encompasses elementary building blocks that are needed for cell growth, as well as a detailed stoichiometric representation of photosynthesis. We demonstrate applicability of iSyn669 for stoichiometric analysis by simulating three physiologically relevant growth conditions of Synechocystis sp. PCC6803, and through in silico metabolic engineering simulations that allowed identification of a set of gene knock-out candidates towards enhanced succinate production. Gene essentiality and hydrogen production potential have also been assessed. Furthermore, iSyn669 was used as a transcriptomic data integration scaffold and thereby we found metabolic hot-spots around which gene regulation is dominant during light-shifting growth regimes.
iSyn669 provides a platform for facilitating the development of cyanobacteria as microbial cell factories.
BMC Systems Biology 11/2010; 4:156. · 3.15 Impact Factor
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Revista de la Facultad de Educación. 01/2010; 17:57-63.
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Joaquina Delás,
Meritxell Notari,
Jaume Forés,
Joaquín Pechuan,
Manuel Porcar,
Emilio Navarro,
Arnau Montagud,
Minerva Baguena,
Juli Peretó, Pedro Fernández de Córdoba,
M Mar González-Barroso,
Eduardo Rial,
Andrés Moya,
Javier Urchueguía
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ABSTRACT: Uncoupling proteins (UCPs) are mitochondrial transporters that facilitate controlled dissipation of the proton gradient and thus regulate energetic efficiency. The heat generating capacity of UCP from brown adipose tissue was investigated in yeasts expressing the protein recombinantly under conditions in which the temperature of the growth medium was measured directly. A Liquid Culture Calorimeter (LCC) was built consisting of a thermally isolated culture flask able to keep yeast cultures warm without resorting to additional heating. The exact internal temperature of the cultures was monitored for 24h through a thermocouple connected to a data logger. Under these conditions, significant temperature increases (1 degrees C) in the media were recorded when yeast strains expressing endogenously active UCP1 mutants were grown. This is the first direct evidence, in a eukaryotic microbial model, of a temperature rise associated with uncoupling activity, and could be seen as the first step toward developing a biological heating device.
New Biotechnology 09/2009; 26(6):300-6. · 2.76 Impact Factor
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ABSTRACT: A solution to the three-dimensional finite line-source (FLS) model for borehole heat exchangers (BHEs) that takes into account the prevailing geothermal gradient and allows arbitrary ground surface temperature changes is presented. Analytical expressions for the average ground temperature are derived by integrating the exact solution over the line-source depth. A self-consistent procedure to evaluate the in situ thermal response test (TRT) data is outlined. The effective thermal conductivity and the effective borehole thermal resistance can be determined by fitting the TRT data to the time-series expansion obtained for the average temperature.
Geothermics 06/2009; 38:263-270. · 1.92 Impact Factor
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International Journal of Hydrogen Energy. 01/2009; 34:8828-38.
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XXXIII Stanford Geothermal Workshop, Stanford University, California, USA; 01/2008
