Aude Silve

• PhD
• PostDoc Position at Karlsruhe Institute of Technology

Background The gradual extrusion of water-soluble intracellular components (such as proteins) from microalgae after pulsed electric field (PEF) treatment is a well-documented phenomenon. This could be utilized in biorefinery applications with lipid extraction taking place after such an ‘incubation’ period, i.e., a post-PEF-treatment step during whi...

BACKGROUND Lipid extraction is a major bottleneck for the commercialization of microalgae due to energy costs involved during solvent recycling. Direct transesterification offers the possibility to bypass the extraction step by immediately converting the lipids to fatty acid methyl esters (FAMEs). In this study, the efficiency of direct transesteri...

Pulsed microwave (PMW) is considered as an energy-saving pretreatment for microalgae. The efficiency of PMW was studied using a generator delivering square-pulsed modulated microwave in continuous flow on fresh Auxenochlorella protothecoides suspension. The efficiency was evaluated by measuring the increase of the suspension's conductivity, the lib...

Novel cell-disruption combinations (autolytic incubation and hypotonic osmotic shock combined with HPH or pH12) were used to investigate the fundamental mass transfer of lipids and proteins from Nannochloropsis slurries (140 mg biomass/g slurry). Since neutral lipids exist as cytosolic globules, their mass transfer was directly dependent on disinte...

This study presents the conception and development of a microwave (MW) applicator based on a TM010 cavity and a pulsed MW source, both custom-designed for evaluation of MW disruption of microalgae. The objective is the selective heating of microalgae immersed in their environment. The applicator enables exposing microalgae suspension to MW in conti...

Background Microalgae have attracted considerable interest due to their ability to produce a wide range of valuable compounds. Pulsed Electric Fields (PEF) has been demonstrated to effectively disrupt the microalgae cells and facilitate intracellular extraction. To increase the commercial viability of microalgae, the entire biomass should be exploi...

This study reports the use of hypotonic osmotic shock as a treatment step to enhance the recoveries of biofuel-convertible lipids and proteins from lipid-rich saltwater Nannochloropsis gaditana (N. gaditana) slurries (biomass content = ~140 mg biomass / g slurry, total lipid content = ~600 mg lipid /g biomass). The osmotic shock was induced through...

This study reports on the use of pulsed electric field (PEF) as a pre-treatment step to enhance lipid extraction yield using extraction with ethanol-hexane blend on fresh oleaginous yeast Saitozyma podzolica. The yeasts were cultivated on nitrogen-depleted condition and had a lipid content of 26.4 ± 4.6% of dry weight. PEF-treatment was applied on...

Pulsed Electric Fields, a known technique for permeabilization of cell membranes, can considerably foster intracellular component extraction from microalgae. However, it is currently uncertain in what way, apart from the cell membrane, the cell wall is affected during pulsation. In this study, fresh Auxenochlorella protothecoides and Chlorella vulg...

Single cell oil (SCO) produced by oleaginous yeasts is considered as a sustainable source for biodiesel and oleochemicals since its production does not compete with food or feed and high yields can be obtained from a wide variety of carbon sources, e.g., acetate or lignocellulose. Downstream processing is still costly preventing the broader applica...

Efficient extraction of valuable products from microalgae and utilization of the residual biomass for biofuel production appear to bring economic benefits for the microalgae biorefineries. The pulsed electric field (PEF) method has been proposed as a promising pre-treatment for microalgae wet extraction. For conversion of microalgae biomass and res...

Amino acids concentrates derived from microalgae biomass through enzymatic protein hydrolysis can improve plant growth by saving the energy that is required for amino acid synthesis from conventional mineral fertilizer resources. To obtain high enzymatic hydrolysis yields, pre-treatment of microalgae biomass prior to enzymatic hydrolysis is suggest...

Pulsed Electric Field (PEF) pre-treatment, applied on fresh microalgae Auxenochlorella protothecoides, induces spontaneous release of a substantial water fraction and enables subsequent lipid extraction using ethanol-hexane blends. In this study, fresh microalgae suspensions were treated with PEF and incubated under inert conditions. Incubation pro...

Microalgae based biofuel is expected to offer new alternatives for renewable energy source. In this study, the effect of pulsed electric field pretreatment (PEF) on microalgae lipid extraction and its further hydrothermal liquefaction (HTL) behavior has been investigated. The samples are defined as No PEF treated algae, PEF treated algae, No PEF tr...

Pulsed Electric Field (PEF) treatment was used as pre-treatment on the microalgae strain Auxenochlorella protothecoides (A.p.) prior to organic solvent extraction of lipids. Experiments were performed on fresh biomass from mixotrophic or autotrophic culture which both had an evaluated lipid content of 30–35% of cell dry weight. Lipid yield was dete...

In this paper, we propose a new dynamical model of tissue electroporation. The model is based on equivalent circuit approach at the tissue. Considering two current densities from cells and extracellular matrix, we identify the macroscopic homogenised contribution of the cell membranes. Our approach makes it possible to define a macroscopic homogeni...

Cell electroporation is a complex phenomenon, which consists in the emergence of defects in cell membranes subjected to electric pulses. Since the end of the 1990s, biophysical models have been developed to explain and predict the conditions for cell electroporation. However the recent biological data, in particular those dealing with the influence...

Human adipose mesenchymal stem cells (haMSCs) are multipotent adult stem cells of great interest in regenerative medicine or oncology. They present spontaneous calcium oscillations related to cell cycle progression or diferentiation but the correlation between these events is still unclear. Indeed, it is difficult to mimic haMSCs spontaneous calciu...

Pulsed electric field (PEF) treatment of microalgae has been demonstrated to exhibit processing advantages compared to conventional processing. Besides low specific energy requirements, PEF treatment can separate microalgae biomass into aqueous and oleaginous fractions. To minimize processing energy demand, the treatment of pre-concentrated microal...

The impact of external medium conductivity on the efficiency of the reversible permeabilisation caused by pulsed electric fields was investigated. Pulses of 12 ns, 102 ns or 100 μs were investigated. Whenever permeabilisation could be detected after the delivery of one single pulse, media of lower conductivity induced more efficient reversible perm...

A dynamic model of electroporation is proposed in order to compute at the tissue scale the distribution of the electric field during the application of the voltage pulse. In this approach, two kinds of density currents are considered: the first one, derived from a model at the cell scale, flows through the cells and the second one flows through the...

When a cell is subjected to an external electric field, a voltage establishes on the membrane and adds to the resting transmembrane voltage (TMV). If the intensity and duration of the external field are sufficient, the membrane becomes conductive, which is the first step in the electroporation process. The increase of conductivity results in a coll...

Cell electroporation is a complex phenomenon, which consists in the emergence of defects in cell membranes subjected to electric pulses. Since the end of the 1990s, biophysical models have been developed to explain and predict the conditions for cell electroporation. However the recent biological data, in particular those dealing with the influence...

Electric pulses of a few nanoseconds in duration can induce reversible permeabilization of cell membrane and cell death. Whether these effects are caused by ionic or purely dielectric phenomena is still discussed. We address this question by studying the impact of conductivity of the pulsing buffer on the effect of pulses of 12ns and 3.2MV/m on the...

The main consequence of the interaction between cells and pulsed electric fields is the destabilization of the plasma membrane leading to its permeabilization. Previous vibrational spectroscopy studies (S.M. Gruenbaum et al., J. Chem. Phys., 135, 2011) have shown that interfacial water is highly organized around the phospholipids of the membrane. M...

Treatment of biological material by pulsed electric fields is a versatile technique in biotechnology and biomedicine used, for example, in delivering DNA into cells (transfection), ablation of tumors, and food processing. Field exposure is associated with a membrane permeability increase usually ascribed to electroporation, i.e., formation of aqueo...

Treatment of biological material by pulsed electric fields is a versatile technique in biotechnology and biomedicine used, for example, in delivering DNA into cells (transfection), ablation of tumors, and food processing. Field exposure is associated with a membrane permeability increase usually ascribed to electroporation, i.e., formation of aqueo...

During somatic differentiation, physiological DNA double-strand breaks (DSB) can drive programmed genome rearrangements (PGR), during which DSB repair pathways are mobilized to safeguard genome integrity. Because of their unique nuclear dimorphism, ciliates are powerful unicellular eukaryotic models to study the mechanisms involved in PGR. At each...

The measurement of transmembrane voltages induced by pulsed electric field exposure can be achieved by using fluorescent dyes like ANNINE-6. Such approach requires a quantitative determination of the fluorescence intensity along the cell´s membrane by image processing. When high temporal resolution is required, the illumination source frequently is...

Applications of cell electropermeabilization are rapidly growing but basic concepts are still unclear. In particular, the impact of electric pulses repetition rate in the efficiency of permeabilisation has not yet been understood. The impact of electric pulses repetition rate in the efficiency of permeabilisation was analysed in experiments perform...

We present here a new model of pore formation based on physical considerations of membrane energy. The idea is to revisit the pore expansion theory, as described by Weaver, Chizmadzhev et al. [4] in the 90's. We first recover the curvature-driven closure of the pore as obtain by Kroeger et al. [2], thanks to Langevin equation written on the pore ar...

Cet article présente un modèle électrique simple de cellule biologique permettant de calculer la tension transmembranaire d'une cellule soumise à un champ électrique extérieur. Dans un premier temps, l'approximation par circuit électrique, qui constitue une approche intuitive du problème, est présentée. L’article indique ensuite comment calculer...

Biologists are involved in electromagnetic fields interactions with human body for therapeutics and health applications. For the defence sector, the objectives aim at identifying the safety thresholds of various electromagnetic waves for future weapons systems. Studies are simultaneously investigated at different levels, from the molecule to the en...

The use of small interfering RNA (siRNA) is a blossoming technique for gene regulation. However, its therapeutic potential is today severely hampered by the lack of an efficient means of safely delivering these nucleic acids to the intracellular medium. We report here that a single 10 ns high-voltage electric pulse can permeabilize lipid vesicles a...

Microsecond-duration electric pulses are widely used for research and therapeutic purposes. The most commonly used device for in vitro exposure to electric pulses is a standard electroporation cuvette. The use of nanosecond-duration electric pulses [nanosecond pulsed electromagnetic fields (nsPEFs) or nanopulses] is an emerging technology. For micr...

This paper demonstrates a new arrangement for wide‐field CARS imaging. The setup using nanosecond dye lasers in a non‐phase‐matching illumination is presented. The chemical selectivity of the signal is demonstrated on polystyrene beads. Moreover, the experimental arrangement has enabled the acquisition of images of living cells in suspension with a...

Permeabilisation by nanosecond electric pulses has been assessed in vitro using several permeabilisation markers. We establish in this paper that reversible permeabilisation by 10 ns pulses can be achieved in vivo. Experiments were performed on tumors. The permeabilisation was assessed by combining a cytotoxic drug (bleomycin) and 10 ns pulses. Alt...

New devices for the controlled application of nanosecond electrical pulses and the detection of their effects on cells. New findings and hypotheses on the parameters controlling the electropermeabilization of biological cells.Abstract:Manipulation of the membranes of cells in suspension or in tissues with electrical pulses is a major research topic...

In our study, we used bleomycin to evaluate the permeabilization caused by nanosecond duration electric pulses (nanopulses). Bleomycin is a non permeant molecule which can be used both as a sensitive and quantitative marker to evaluate cell electropermeabilization. Indeed, the penetration of as few as 500 molecules is sufficient to entail a major b...

Intense (several MV/m) nanosecond duration electric pulses can induce damages on cells external membrane which can be detected by direct cell killing or by the uptake of non permeant molecules. We detail here the methodology to carry out those experiments, drawing the attention to exposure artifacts that demonstrate the importance of the implementa...

Electropermeabilisation of cells can be obtained by electric pulses of very different durations. In this paper we compare the efficiency of pulses of 100 µs and 10 ns duration eventually in the presence of bleomycin, a cytotoxic drug in order to detect reversible permeabilisation of cells. Biological effects are evaluated using cloning efficiency t...

During the sexual cycle of the ciliate Paramecium, assembly of the somatic genome includes the precise excision of tens of thousands of short, non-coding germline sequences (Internal Eliminated Sequences or IESs), each one flanked by two TA dinucleotides. It has been reported previously that these genome rearrangements are initiated by the introduc...

This paper deals with the development of a microfluidic biochip for the exposure of living cells to nanosecond pulsed electric fields (nsPEF). When exposed to ultra short electric pulses (typical duration of 3-10ns), disturbances on the plasma membrane and on the intra cellular components occur, modifying the behavioral response of cells exposed to...

The cell membrane is an impassable barrier for small hydrophilic molecules, termed ­nonpermeant, that are too hydrophilic for diffusing through the plasma membrane, and moreover are not recognized and internalized by a transporter, channel, or receptor system. Reversible cell electropermeabilization allows the cellular uptake of these nonpermeant s...

In this paper permeabilisation of potato tissue caused by either microsecond electric pulses or nanosecond electric pulses is compared. The intensity of permeabilisation is quantified by means of bio-impedance change. Thanks to this method, the impact of the repetition frequency was investigated. Data show that very low repetition frequencies can b...

Survival of mammalian cells is achieved by tight control of cell volume while transmembrane potential is known to control many cellular functions since the seminal work of Hodgkin and Huxley. Regulation of cell volume and transmembrane potential have a wide range of implications in physiology, from neurological and cardiac disorders to cancer and m...

Survival of mammalian cells is achieved by tight control of cell volume, while transmembrane potential has been known to control many cellular functions since the seminal work of Hodgkin and Huxley. Regulation of cell volume and transmembrane potential have a wide range of implications in physiology, from neurological and cardiac disorders to cance...

An exposure system for a nanosecond pulsed electric field is presented and completely characterized in this paper. It is composed of a high-voltage generator and an applicator: the biological cuvette. The applied pulses have high intensities (up to 5 kV), short durations (3 and 10 ns), and different shapes (square, bipolar). A frequency characteriz...

A great interest has recently emerged concerning the interactions between nanosecond electric pulses and biological cells. The duration of the pulses currently used ranges from a few nanoseconds to a few hundreds of nanoseconds, but sub-nanosecond pulses effects are starting to be explored. In this paper we propose an electric field sensor well ada...