Biomass monitoring using multifrequency impedance measurements: relationship between particle size and electric impeadance

Authors: Gamez, X. Sabes, M. Bragos, R. Riu, P.J. Cairo, J.J. G̣dia. F.

Journal:Conference Proceedings ...

Conf. title:1st European Symposium on Biochemical Engineering Science. Conf date: Sept. 19-21 1996 Conf. Loc.: Dublin, Ireland.

Abstract: Great attention has been paid towards the development and improvement of measurements devices for on-line monitoring of biomass concentration in biotechnological processes. Among the systems for biomass measurements, the dielectrical analysis of cell suspensions is an attractive technique in order to estimate the cellular concentration because is a real time and automated monitoring system and ampplicable to complex media.
The tecnique used in this work is based on the measurements of the relaxation drop of the impedance of cellular membranes caused when a multifrequency electrical current is injected to the sample. Using this technique, it has been observed a different electrical behaviour between yeast and bacterial cells in front of the dielectrical measurement described. With the goal of better undertandign the basis of the phenomena taking place, liposomen are proposed as an experimental model to mock the response of cell membranes. They have the adventage to provide a very well defined particle size and constant measurements conditions.
The result presented show the relationship existing between the size of liposomes and the obtyained impedance measurements, and will be used to discuss the results obtained with yeast and bacterial cells.