C. Schultheiss, H.-J. Bluhm and H.-G. Mayer*

Forschungszentrum Karlsruhe GmbH, Institute for Pulsed Power and Microwave Technology,

*Technology Transfer and Marketing, Postfach 3640, D-76021 Karlsruhe, Germany

M. Kern, Fa. Lutz & Kern, Saarstrasse 4, D-68753 Waghäusel-Kirrlach, Germany

Electroporation (EP) of biological cells is of increased importance in the area of bio-technology. By the application of 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 built-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 talk is firstly to report on experiments at the industrial electroporation pilot systems KEA [1] with whole plants [2]. Experiences are collected with beets, apples, grapes etc.. Secondly design studies for an industrial EP production device will be presented. The amount of plant material, which must be treated is in the order of 1 t/min. Since plants, as for example beets, are large in diameter and nearly weightless in water (suspension), the size of an electroporation reactor has to be large and the plants must be transported continuously by means of a forced feed-through. This calls for very high voltage pulses to establish reactor fields in the order of 20 kV/cm in the 30 cm gap as well as high pulse repetition rates to fulfill power demands. At the Forschungszentrum Karlsruhe 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 kV, the pulse length is 1 µs and the pulsed energy fed into a 20 Ohm load is about 1 kJ. The life time of the electric components is designed to withstand minimum up to 200 million discharge cycles (3 month operation). The system consisting of the electroporation reactor plus conveyance is designed to be mainly built from dielectric materials to avoid undesired shielding effects of the electric field in the area of the reactor chamber. However high voltage strength dielectric material like polyethylene or polypropylene underlie enhanced mechanical wear which must be taken into account.