Consulta: creatorFacets:"Bernard, Olivier"
Registros recuperados: 13
Data/hora: 17/06/2024 09:50:43

How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments
Provedor de dados: 5
Autores: Demory, David; Combe, Charlotte; Hartmann, Philipp; Talec, Amelle; Pruvost, Eric; Hamouda, Raouf; Souille, Fabien; Lamarea, Pierre-olivier; Bristeau, Marie-odile; Sainte-marie, Jacques; Rabouille, Sophie; Mairet, Francis; Sciandra, Antoine; Bernard, Olivier.
Hydrodynamics in a high-rate production reactor for microalgae cultivation affects the light history perceived by cells. The interplay between cell movement and medium turbidity leads to a complex light pattern, whose forcing effects on photosynthesis and photoacclimation dynamics are nontrivial. Hydrodynamics of high density algal ponds mixed by a paddle wheel has been studied recently, although the focus has never been on describing its impact on photosynthetic growth efficiency. In this multidisciplinary downscaling study, we first reconstructed single cell trajectories in an open raceway using an original hydrodynamical model offering a powerful discretization of the Navier-Stokes equations tailored to systems with free surfaces. The trajectory of a...
Tipo: Text
Palavras-chave: Photosynthesis; Hydrodynamics; Modelling; Photoacclimation; Dunaliella salina; Non-photochemical quenching.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00445/55692/57352.pdf

Screening and selection of growth-promoting bacteria for Dunaliella cultures
Provedor de dados: 5
Autores: Le Chevanton, Myriam; Garnier, Matthieu; Bougaran, Gael; Schreiber, Nathalie; Lukomska, Ewa; Berard, Jean-baptiste; Fouilland, E.; Bernard, Olivier; Cadoret, Jean-paul.
Previous studies have demonstrated that bacteria influence microalgal metabolism, suggesting that the selection and characterization of growth-promoting bacteria should offer a new strategy for improving industrial algal cultivation. In the present study, 48 cultivable bacteria were isolated from marine microalgae species and identified using 16S rRNA phylogenetic analysis. The recovered bacteria were found to be members of the α- and γ-Proteobacteria, Cytophaga–Flavobacterium–Bacteroides (CFB) and gram-positive monophyletic clusters. To address the effect of these bacteria on the growth of Dunaliella sp. individually, an experimental high-throughput tool was developed to simultaneously compare replicated associations. A two-step approach was used to...
Tipo: Text
Palavras-chave: Microalgae; Dunaliella; Bacteria; Interaction; Bacterial diversity.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00142/25334/24768.pdf

Maximizing microalgae productivity in a light-limited chemostat
Provedor de dados: 5
Autores: Martinez, Carlos; Bernard, Olivier; Mairet, Francis.
Light supply is one of the most important parameters to be considered for enhancing microalgae growth in photobioreactors (PBR) with artificial light. However, most of the mathematical works do not consider incident light as a parameter to be optimized. In this work based on a simple model of light-limited growth, we determine optimal values for the dilution rate and the incident light intensity in order to maximize the steady-state microalgal surface productivity in a continuous culture. We also show that in optimal conditions there is a minimal initial microalgal concentration (and we give a simple expression to determine it) to guarantee the persistence of the population. Finally, in the context of enhancing microalgae productivity by reducing light...
Tipo: Text
Palavras-chave: Dynamics and control; Industrial biotechnology; Photoinhibition; Biomass productivity; Microalgae; Photoacclimation; Chlorophyll.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00439/55091/56653.pdf

Dynamics and control of a periodically forced microalgae culture
Provedor de dados: 5
Autores: Martínez, Carlos; Mairet, Francis; Martinon, Pierre; Bernard, Olivier.
Microalgae cultivation with wastewater is a promising way of reducing the energetic needs for wastewater treatment and the costs of biofuel production. However, the very turbid medium is not favorable for the development of microalgae. Indeed, light, the key element for photosynthesis, rapidly vanishes along depth due to absorption and scattering. Therefore it is crucial to understand the effects of the depth on turbid cultures. In this work, we study theoretically the long-term behavior of a continuous culture of microalgae exposed to a periodic source of light. By allowing periodic variations of the depth and the hydraulic retention time, we show that the microalgae population is forced to a periodic regime. Finally, we address numerically the problem of...
Tipo: Text
Palavras-chave: Dynamics and control; Industrial biotechnology; Wastewater; Biomass productivity; Microalgae.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00505/61623/65654.pdf

Modeling continuous cultures of microalgae colimited by nitrogen and phosphorus
Provedor de dados: 5
Autores: Bougaran, Gael; Bernard, Olivier; Sciandra, Antoine.
It is well documented that the combination of low nitrogen and phosphorus resources can lead to situations where colimitation of phytoplankton growth arises, yet the underlying mechanisms are not fully understood. Here, we propose a Droop-based model built on the idea that colimitation by nitrogen and phosphorus arises from the uptake of nitrogen. Indeed, since N-porters are active systems, they require energy that could be related to the phosphorus status of the cell. Therefore, we assumed that N uptake is enhanced by the P quota. Our model also accounts for the biological observations that uptake of a nutrient can be down-regulated by its own internal quota, and succeeds in describing the strong contrast for the non-limiting quotas under N-limited and...
Tipo: Text
Palavras-chave: Colimitation; Phytoplankton; Mathematical model; Quota.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00011/12216/9060.pdf

Quantifying the potential of microalgae to remove nutrients from wastewater
Provedor de dados: 5
Autores: Martinez, Carlos; Mairet, Francis; Plaza, Luis; Sciandra, Antoine; Bernard, Olivier.
The main resources limiting microalgae growth are typically phosphorus, nitrogen, and light. Based on the theory of the light limited chemostat, the variable cell quota approach, and photoacclimation models, we build a mathematical model for describing microalgae growth under limitation by these resources. The model is calibrated with a data set from the literature. Then, by numerical simulations, we find that under constant operation of the culture and constant environmental conditions (illumination, temperature, pH, etc.), solutions of the model approach towards either a positive or an extinction steady state. Based on the positive steady state, and in the context of wastewater treatment, we evaluate the capacity of microalgae to remove contaminants. We...
Tipo: Text
Palavras-chave: Control; Biotechnology; Wastewater treatment; Microalgae; Cell quota model.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00600/71188/69541.pdf

The use of fluorescent Nile red and BODIPY for lipid measurement in microalgae
Provedor de dados: 5
Autores: Rumin, Judith; Bonnefond, Hubert; Saint-jean, Bruno; Rouxel, Catherine; Sciandra, Antoine; Bernard, Olivier; Cadoret, Jean-paul; Bougaran, Gael.
Microalgae are currently emerging as one of the most promising alternative sources for the next generation of food, feed, cosmetics and renewable energy in the form of biofuel. Microalgae constitute a diverse group of microorganisms with advantages like fast and efficient growth. In addition, they do not compete for arable land and offer very high lipid yield potential. Major challenges for the development of this resource are to select lipid-rich strains using high-throughput staining for neutral lipid content in microalgae species. For this purpose, the fluorescent dyes most commonly used to quantify lipids are Nile red and BODIPY 505/515. Their fluorescent staining for lipids offers a rapid and inexpensive analysis tool to measure neutral lipid content,...
Tipo: Text
Palavras-chave: Nile red; BODIPY 505/515; Microalgae; Neutral lipid; Fluorescence; Biodiesel.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00257/36823/35451.pdf

Twelve quick tips for designing sound dynamical models for bioprocesses
Provedor de dados: 5
Autores: Mairet, Francis; Bernard, Olivier.
Because of the inherent complexity of bioprocesses, mathematical models are more and more used for process design, control, optimization, etc. These models are generally based on a set of biochemical reactions. Model equations are then derived from mass balance, coupled with empirical kinetics. Biological models are nonlinear and represent processes, which by essence are dynamic and adaptive. The temptation to embed most of the biology is high, with the risk that calibration would not be significant anymore. The most important task for a modeler is thus to ensure a balance between model complexity and ease of use. Since a model should be tailored to the objectives, which will depend on applications and environment, a universal model representing any...
Tipo: Text
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00512/62336/66596.pdf

Theory of turbid microalgae cultures.
Provedor de dados: 5
Autores: Martinez, Carlos; Mairet, Francis; Bernard, Olivier.
Microalgae can be cultivated in closed or open photobioreactors (PBR). In these systems, light rapidly decreases as it passes through the culture due to the turbidity of the medium. Thus, microalgae experiment different light intensities depending on their position in the medium. In this paper, we study theoretically how the growth rate of microalgae is affected by different factors; incident light intensity, form of the PBR, microalgae population density, turbidity of non-microalgae components, and light path-length of the reactor. We show that for different types of PBR the average growth rate is completely determined by the incident light intensity and the optical depth. In the case of vertical cylindrical PBRs illuminated from above (e.g. race-way or...
Tipo: Text
Palavras-chave: Photobioreactor; Optical depth; Photoinhibition; Light limitation; Turbidity; Modelling.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00450/56133/57675.pdf

Phytoplankton growth formulation in marine ecosystem models: Should we take into account photo-acclimation and variable stoichiometry in oligotrophic areas?
Provedor de dados: 5
Autores: Ayata, S. -d.; Levy, Marina; Aumont, Olivier; Sciandra, Antoine; Sainte-marie, J.; Tagliabue, A.; Bernard, Olivier.
The aim of this study is to evaluate the consequences of accounting for variable Chl:C (chlorophyll:carbon) and C:N (carbon:nitrogen) ratios in the formulation of phytoplankton growth in biogeochemical models. We compare the qualitative behavior of a suite of phytoplankton growth formulations with increasing complexity: 1) a Redfield formulation (constant C:N ratio) without photo-acclimation (constant Chl:C ratio), 2) a Redfield formulation with diagnostic chlorophyll (variable and empirical Chl:C ratio), 3) a quota formulation (variable C:N ratio) with diagnostic chlorophyll, and 4) a quota formulation with prognostic chlorophyll (dynamic variable). These phytoplankton growth formulations are embedded in a simple marine ecosystem model in a 1D framework...
Tipo: Text
Palavras-chave: Biogeochemical modeling; Phytoplankton; Photo-acclimation; Redfield ratio; Internal quota; BATS; Optimization; Micro-genetic algorithm.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00159/27071/25460.pdf

Dynamics of the periodically forced light-limited Droop model
Provedor de dados: 5
Autores: Martinez, Carlos; Mairet, Francis; Bernard, Olivier.
The periodically forced light-limited Droop model represents microalgae growth under co-limitation by light and a single substrate, accounting for periodic fluctuations of factors such as light and temperature. In this paper, we describe the global dynamics of this model, considering general monotone growth and uptake rate functions. Our main result gives necessary and sufficient conditions for the existence of a positive periodic solution (i.e. a periodic solution characterized by the presence of microalgae) which is globally attractive. In our approach, we reduce the model to a cooperative planar periodic system. Using results on periodic Kolmogorov equations and on monotone sub-homogeneous dynamical systems, we describe the global dynamics of the...
Tipo: Text
Palavras-chave: Variable quota model; Positive periodic solution; Global stability; Microalgae; Cooperative system.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00599/71140/69455.pdf

Continuous selection pressure to improve temperature acclimation of Tisochrysis lutea
Provedor de dados: 5
Autores: Bonnefond, Hubert; Grimaud, Ghjuvan; Rumin, Judith; Bougaran, Gael; Talec, Amelie; Gachelin, Manon; Boutoute, Marc; Pruvost, Eric; Bernard, Olivier; Sciandra, Antoine.
Temperature plays a key role in outdoor industrial cultivation of microalgae. Improving the thermal tolerance of microalgae to both daily and seasonal temperature fluctuations can thus contribute to increase their annual productivity. A long term selection experiment was carried out to increase the thermal niche (temperature range for which the growth is possible) of a neutral lipid overproducing strain of Tisochrysis lutea. The experimental protocol consisted to submit cells to daily variations of temperature for 7 months. The stress intensity, defined as the amplitude of daily temperature variations, was progressively increased along successive selection cycles. Only the amplitude of the temperature variations were increased, the daily average...
Tipo: Text
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00404/51506/52107.pdf

Getting the most out of it: Optimal experiments for parameter estimation of microalgae growth models
Provedor de dados: 5
Autores: Munoz-tamayo, Rafael; Martinon, Pierre; Bougaran, Gael; Mairet, Francis; Bernard, Olivier.
Mathematical models are expected to play a pivotal role for driving microalgal production towards a profitable process of renewable energy generation. To render models of microalgae growth useful tools for prediction and process optimization, reliable parameters need to be provided. This reliability implies a careful design of experiments that can be exploited for parameter estimation. In this paper, we provide guidelines for the design of experiments with high informative content based on optimal experiment techniques to attain an accurate parameter estimation. We study a real experimental device devoted to evaluate the effect of temperature and light on microalgae growth. On the basis of a mathematical model of the experimental system, the optimal...
Tipo: Text
Palavras-chave: Biofuel; Biological processes; Modelling; Parameter identification; Optimal experiment design.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00191/30252/28684.pdf