Extraction of energetic molecules from micro-algae, combining the use of electrical field solicitations and mechanical stress within a microfluidic device

Les microalgues présentent un vrai potentiel d’innovation dans les principaux secteurs industriels tel que l’énergie, l’agroalimentaire, la cosmétique et la santé. Elles sont considérées comme étant la solution privilégiée pour répondre aux besoins énergétiques futurs et ainsi permettre une transition des énergies fossiles vers les énergies renouvelables. Néanmoins, les systèmes de production à grande échelle à partir de microalgues nécessitent encore des améliorations afin de les rendre économiquement compétitifs et durables tout en préservant l’environnement.Ainsi, l’objectif de cette thèse consiste à évaluer une nouvelle voie pour l’extraction de composés d’intérêt à partir de microalgues et de caractériser leur performance en termes d’efficacité d’extraction. L’utilisation combinée de champs électriques pulsés, et de compressions mécaniques (à travers un système microfluidique dédié) en tant que prétraitements à l’extraction de composés lipidiques, riches en énergie, produits par la microalgue Chlamydomonas reinhardtii, a donc été étudiée. Les mécanismes mis en jeu, à l’échelle de la cellule, ont été mis en évidence.Ce projet de thèse s’est déroulé dans le contexte d’une collaboration entre les laboratoires SATIE de l’ENS Paris-Saclay et LGPM de CentraleSupélec Paris-Saclay.Les résultats obtenus ont permis de confirmer le potentiel des technologies utilisées dans l’amélioration du rendement d’extraction de l’huile algale. Cette étude démontre notamment le rôle important de la paroi cellulaire de l’algue en tant qu’obstacle à une extraction optimale. Une étude approfondie de sa réponse physiologique aux prétraitements et aux conditions de stress est proposée.Microalgae have a real potential in the innovation of the main industrial sectors such as energy, food, cosmetics and health. They are considered as a promising solution to meet future energy needs and thus enable a transition from fossil to renewable energies. Nevertheless, large scale production systems using microalgae still need improvements to become economically competitive and sustainable while preserving the environment.Thus, the aim of this thesis is to evaluate an innovative approach for the extraction of compounds of interest from microalgae and characterize their performance in terms of extraction efficiency. The effect of combining pulsed electric fields and mechanical compressions (through a dedicated microfluidic system) as pretreatments for the extraction of lipids, energy-rich compounds produced by the microalga Chlamydomonas reinhardtii, was therefore studied. The mechanisms involved, at the cellular scale, were highlighted.This project took place in the context of a collaboration between the laboratories SATIE of ENS Paris-Saclay and LGPM of CentraleSupélec Paris-Saclay.The obtained results have confirmed the potential of the technologies to improve the algal oil extraction. Furthermore, this study demonstrates the important role of the algae’s cell wall as an obstacle to an optimal extraction. A comprehensive study of the microalgae’s physiological response to pretreatments and stress conditions is proposed

Extraction de composés énergétiques à partir de microalgues par application conjuguée d’impulsions de champ électrique et de sollicitations mécaniques dans un système microfluidique.

Microalgae have a real potential in the innovation of the main industrial sectors such as energy, food, cosmetics and health. They are considered as a promising solution to meet future energy needs and thus enable a transition from fossil to renewable energies. Nevertheless, large scale production systems using microalgae still need improvements to become economically competitive and sustainable while preserving the environment.Thus, the aim of this thesis is to evaluate an innovative approach for the extraction of compounds of interest from microalgae and characterize their performance in terms of extraction efficiency. The effect of combining pulsed electric fields and mechanical compressions (through a dedicated microfluidic system) as pretreatments for the extraction of lipids, energy-rich compounds produced by the microalga Chlamydomonas reinhardtii, was therefore studied. The mechanisms involved, at the cellular scale, were highlighted.This project took place in the context of a collaboration between the laboratories SATIE of ENS Paris-Saclay and LGPM of CentraleSupélec Paris-Saclay.The obtained results have confirmed the potential of the technologies to improve the algal oil extraction. Furthermore, this study demonstrates the important role of the algae’s cell wall as an obstacle to an optimal extraction. A comprehensive study of the microalgae’s physiological response to pretreatments and stress conditions is proposed.Les microalgues présentent un vrai potentiel d’innovation dans les principaux secteurs industriels tel que l’énergie, l’agroalimentaire, la cosmétique et la santé. Elles sont considérées comme étant la solution privilégiée pour répondre aux besoins énergétiques futurs et ainsi permettre une transition des énergies fossiles vers les énergies renouvelables. Néanmoins, les systèmes de production à grande échelle à partir de microalgues nécessitent encore des améliorations afin de les rendre économiquement compétitifs et durables tout en préservant l’environnement.Ainsi, l’objectif de cette thèse consiste à évaluer une nouvelle voie pour l’extraction de composés d’intérêt à partir de microalgues et de caractériser leur performance en termes d’efficacité d’extraction. L’utilisation combinée de champs électriques pulsés, et de compressions mécaniques (à travers un système microfluidique dédié) en tant que prétraitements à l’extraction de composés lipidiques, riches en énergie, produits par la microalgue Chlamydomonas reinhardtii, a donc été étudiée. Les mécanismes mis en jeu, à l’échelle de la cellule, ont été mis en évidence.Ce projet de thèse s’est déroulé dans le contexte d’une collaboration entre les laboratoires SATIE de l’ENS Paris-Saclay et LGPM de CentraleSupélec Paris-Saclay.Les résultats obtenus ont permis de confirmer le potentiel des technologies utilisées dans l’amélioration du rendement d’extraction de l’huile algale. Cette étude démontre notamment le rôle important de la paroi cellulaire de l’algue en tant qu’obstacle à une extraction optimale. Une étude approfondie de sa réponse physiologique aux prétraitements et aux conditions de stress est proposée

Influence of temperature on Chlorella vulgaris growth and mortality rates in a photobioreactor

International audienceThe ability of microalgae to fix carbon dioxide and convert it into biofuels, foods and other valuable products has drawn a lot of scientific attention in the last decades. In the last years a number of works aimed at understanding the influence of daily and seasonal temperature fluctuations that affect cell metabolism, and thus biomass production efficiency, have been carried out. However the impact of temperature on cell mortality has never been considered, while temperatures higher than the optimal growth temperature are often reached in summer for outdoor cultivation. This paper explores the effect of high temperatures both on mortality and growth for cultures of Chlorella vulgaris in a photobioreactor. Viability was measured with fluorescein diacetate (FDA), and thus mortality and growth rates were estimated, together with chlorophyll a and intracellular contents in carbon and nitrogen. While the fraction of viable cells decreased at higher temperatures, viable growth and mortality increased from 20 degrees C to 28 degrees C. Chl(a):Cresults suggest that temperature induced photoacclimation in the viable fraction of cells at higher temperatures. A Hinshelwood model was fitted to the data and appropriately described the mortality increase with temperature. Mechanisms affecting growth and mortality rates at high temperature are then discussed

Revealing the Friction Stress of Microalgae in Microfluidic Devices through Mechanofluorochromism

Polydiacetylenes are deeply investigated for their mechanofluorochromic behavior: the blue, non-emitting solid phase, obtained by photopolymerization of the diacetylene precursor, is converted to the red, emitting one by a mechanical stimulus. Inspired by the great potentiality of these compounds to act as microscale force probes, the mechanofluorochromism is implemented in microalgae biotechnology. Indeed, mechanical solicitations in a microfluidic chip can weaken the cellular envelope and facilitate the extraction of high-added value compounds produced by the microalgae. Herewith, a polydiacetylene-based mechanofluorochromic sensor is reported to be able to detect the stress applied to microalgae in microchannels. A triethoxysilane diacetylene precursor is designed that photopolymerizes in a purple, low-emissive phase, and is converted to the red, high-emissive phase upon mechanical stress. Hereafter, a protocol is set up to chemically graft in the microfluidic channels a polydiacetylene layer, and eventually proves that upon compression of Chlamydomonas reinhardtii microalgae in restricted areas, the friction stress is revealed by the mechanofluorochromic response of the polydiacetylene, leading to a marked fluorescence enhancement up to 83%. This prototype of microscale force probes lays the ground for microscale stress detection in microfluidics environments, which can be applied not only to microalgae but also to any mechano-responsive cellular sample

Characterizing single sinonasal squamous cell carcinoma using dielectrophoresis and electrorotation

International audienceWe show the capture and analysis single cells, in particular human sinonasal squamous cell carcinomas (SCC), by the combination of di-electrophoresis (DEP) force and electrorotation, within a microfluidic device. A set of 4 planar polynomial electrodes was employed to perform nDEP trapping of two lines tumor cell with different invasivity, named NC5 and NC7. Once captured at the center of the electrodes set, electrorotation was served to extract the rotational speed's spectra. From the spectra, their electrophysiological properties can be estimated

In situ and real time electroporation of a lipid producing microalgae in a microfluidic device

International audienc

Impact of pulsed electric fields and mechanical compressions on the permeability and structure of Chlamydomonas reinhardtii cells

International audienceCurrent research findings clearly reveal the role of the microalga's cell wall as a key obstacle to an efficient and optimal compound extraction. Such extraction process is therefore closely related to the microalga species used. Effects of electrical or mechanical constraints on C. reinhardtii's structure and particularly its cell wall and membrane, is therefore investigated in this paper using a combination of microscopic tools. Membrane pores with a radius between 0.77 and 1.59 nm were determined for both reversible (5 kV•cm −1) and irreversible (7 kV•cm −1) electroporation with a 5 µs pulse duration. Irreversible electroporation with longer pulses (10 µs) lead to the entry of large molecules (at least 5.11 nm). Additionally, for the first time, the effect of pulsed electric fields on the cell wall was observed. The combined electrical and mechanical treatment showed a significant impact on the cell wall structure as observed under Transmission Electron Microscopy. This treatment permits the penetration of larger molecules (at least 5.11 nm) within the cell, shown by tracking the penetration of dextran molecules. For the first time, the size of pores on the cell membrane and the structural changes on the microalgae cell wall induced by electrical and mechanical treatments is reported

Characterization of Chlamydomonas Reinhardtii's cell wall and membrane permeability after PEF treatment and mechanical compressions within a microfluidic device

International audienc

Characterization of Chlamydomonas Reinhardtii's cell wall and membrane permeability after PEF treatment and mechanical compressions within a microfluidic device

International audienc