Transient and stable electrotransformations of intact black Mexican sweet maize cells are obtained after preplasmolysis

Energy-efficient biomass processing with pulsed electric fields for bioeconomy and sustainable development

Fossil resources-free sustainable development can be achieved through a transition to bioeconomy, an economy based on sustainable biomass-derived food, feed, chemicals, materials, and fuels. However, the transition to bioeconomy requires development of new energy-efficient technologies and processes to manipulate biomass feed stocks and their conversion into useful products, a collective term for which is biorefinery. One of the technological platforms that will enable various pathways of biomass conversion is based on pulsed electric fields applications (PEF). Energy efficiency of PEF treatment is achieved by specific increase of cell membrane permeability, a phenomenon known as membrane electroporation. Here, we review the opportunities that PEF and electroporation provide for the development of sustainable biorefineries. We describe the use of PEF treatment in biomass engineering, drying, deconstruction, extraction of phytochemicals, improvement of fermentations, and biogas production. These applications show the potential of PEF and consequent membrane electroporation to enable the bioeconomy and sustainable development.

Electroporation modulates the embryogenic responses of asparagus (Asparagus officinalis L.) microspores

Microspores of three genotypes of Asparagus officinalis L. were mechanically isolated without affecting their viability and were submitted to electric fields in order to modulate their competence for embryogenesis. When a constant pulse length and various field strengths (250, 500, 750, 1000, 1500, and 2000 V/cm) were tested, the viability of electro-treated microspores decreased as the field strength increased, for all genotypes. Conversely, the embryogenic competence was genotype dependent and was enhanced by low voltages for two clones when microspores were cultured in the presence of auxin. When the effect of pulse duration was studied, despite a strong genotype effect on responses, a short pulse coupled with a low voltage appeared to improve the competence for proembryo formation compared with nonelectroporated microspores, while longer pulses significantly improved microspore division.

Electrooptics studies of Escherichia coli electropulsation: orientation, permeabilization, and gene transfer

Fast optical transient signals are suitable approaches to the investigation of the behavior of bacteria during an electric pulse. In a previous work, by a dual approach taking advantage of a video method and a fast kinetic study of the light transmitted across a cell suspension, we showed that a field-induced orientation phenomenon was affecting the rod-shaped bacteria during the pulse (Eynard et al., 1992. Eur. J. Biochem. 209:431-436). In the present work, time courses of electro-induced responses of bacteria during a single square-wave pulse are analyzed. Observations of both the orientation step and the permeabilization process are relevant. These two steps are affected by the addition of DNA. They both obey to a first-order kinetic. The conclusion of this work is that Escherichia coli permeabilization and transformation are multistep processes: orientation (step 1) is followed by an envelope alteration (step 2), all steps being affected by plasmid addition. In the case of E. coli, a rod-shaped bacteria, the orientation process (step 1) brings the cell parallel to the field direction. The pulse duration must be longer than the orientation characteristic time (approximately 1 ms) to trigger an effective permeabilization and its associated events. The permeabilization process (step 2) is associated with a field-induced dipole effect.