Development of an industrial electroporation device

Electroporation (EP) of biological cells is of increasing importance in the area of bio-technology. By applying external electric fields along biological cells in a water suspension the cytoplasm becomes polarized. The charge displacement in the cytoplasm and in the suspension leads to high transmembrane potentials in the order of several volts. The build-up of large irreversible openings in the cell membrane, the flow-out of cytoplasm and the cell-perish are the desired effects. The subject of this paper is i) to report on experiments at an EP system with whole crop plants. Experiences have been gained already with sugar beets, apples, grapes, etc., ii) to present design studies for an industrial EP production device. The amount of plant material, which must be treated is in the order of 1 t/min. Since crop plants, such as sugar beets, are large in diameter and nearly weightless in water (suspension), the size of an EP reactor has to be large and the plants must be moved continuously by means of a forced feed-through. This requires very high voltage pulses to establish reactor field strengths of about 20 kV/cm in the 30 cm gap, as well as high pulse repetition rates to fulfill power demands. At the Forschungszentrum Karlsruhe several types of Marx generators with gas spark gaps have been developed and tested. They run with pulse frequencies in the order of 20-30 Hz. The pulse amplitude is 300 W, the pulse length is 1 μs and the pulsed energy fed into a 20 load is about 1 kJ. The lifetime of the electric components is designed to withstand at least up to 200 million discharge cycles (3 month operation). The system consisting of the EP reactor plus conveyance is designed to be built up mainly of dielectric materials to avoid undesired shielding effects of the electric field in the area of the reactor chamber. However high voltage-proof dielectric materials such as polyethylene or polypropylene underlie enhanced mechanical wear which must be taken into account.