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 has become a rapidly developing area of biotechnology. If external electric fields are applied across 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. As a result large irreversible openings can built-up in the cell membrane, the cytoplasm can flow-out of and the cell can perish.

The subject of this talk is firstly to report on actual experiments at the mobile industrial electroporation pilot system KEA (Karlsruhe Elektroporation Anlage) with whole plants[1]. The maximum throughput of this device is 2 tons/hour. The reactor is a 16 cm-tube with integrated electrode pairs, where pulses with amplitudes up to 300 kV are applied at a repetition rate of 7 Hz. An overview of results from treated plants like beets, apples, grapes etc. will be given.

Secondly, design studies, development and test of an industrial EP production device will be presented. Since plants, as for example beets, are large in diameter and nearly weightless in water (suspension), the size of an electroporation reactor gap has to be large and the plants must be transported continuously by means of a forced feed-through. In the test facility ZAR (Zell Aufschluss Reaktor) a throughput in the order of 1 ton/min has been demonstrated. The operation of such a powerful device with a reactor spacing of 30 cm needs an assembly of Marx generators with high pulse repetition rates to establish fields at the reactor site as well as to fulfill power demands.

At Forschungszentrum Karlsruhe different types of Marx generators with gas spark gaps have been developed and tested. They are able to run with pulse frequencies in the order of 20-30 Hz (test Marx generator with 100 kV pulses). The pulse amplitude needed is 350 kV, the pulse length is 1 µs and the pulse energy fed into a 20 Ohm load is about 1 kJ. The life time of the electric components is designed to withstand a minimum of up to 200 million discharge cycles (3 month operation). The complete system consisting of 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 materials like polyethylene or polypropylene underlie enhanced mechanical wear which must be taken into account.