Processing of sugar beet cells with strong electric fields

1. Principles of electroporation and development of industrial devices

C. Schultheiss, H.-J. Bluhm, M. Sack 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 increasing importance in the area of biotechnology. If external electric fields are applied to biological cells in a water suspension the cell cytoplasm becomes polarized. The charge displacement in the cytoplasm as well as 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 results in the flow-out of cytoplasm and cell-perish. 


The subject of this talk is first to report on fundamentals of electroporation and experiments with the mobile laboratory-scale electroporation pilot systems KEA (Karlsruhe Elektroporations Anlage) with entire sugar beets. The maximum throughput of this device is 2 tons/hour. The reactor is a 16 cm-tube with four integrated electrode pairs, where pulses with up to 300 kV can be applied with a repetition rate of 7 Hz.  Summary of results and experience of the treatment of sugar beets will be given in the second part.


Second, design studies, development and test for an industrial EP production facility will be presented. Since plants, like 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 rate to establish fields at the reactor site as well as to fulfill power demands.


At the 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), respectively with 14 Hz (350 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 at least 200 million discharge cycles (3 month operation). The system consisting of an 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.