Monitoring of Saccharomyces cerevisiae viability by non-Faradaic impedance spectroscopy using interdigitated screen-printed platinum electrodes

Interdigitated, screen-printed platinum microelectrodes are used for non-Faradaic impedance spectroscopy detection of viable Saccharomyces cerevisiae. The time dependence of the complex impedance of both living and heat-inactivated yeast cells immersed in plain medium or immobilized in agar is measured between 0.01 Hz and 1 MHz for 300 min. To understand the processes probed by the impedance measurement, an equivalent electrical circuit, containing a constant phase element, a charge transfer resistance and a suspension resistance, is established and analyzed. For both heat-inactivated and living yeast cells in plain medium, the suspension resistance increases over time caused by sedimentation of the yeast cells into the stray field of the electrodes. The measured increase is found to be larger for living cells than for heat-inactivated ones. The time dependence of the double-layer capacitance is rather dominated by the metabolic activity of living cells, but a possible impact of cell sedimentation cannot be completely neglected. In experiments carried out with cells immobilized in agar, cell sedimentation is suppressed, and thus, the time evolution of the double-layer capacitance is solely caused by metabolic active cells. Therefore, the time-dependent change of the double-layer capacitance can be used to directly monitor the viability of Saccharomyces cerevisiae in situ, since inactivated cells do not contribute to the signal generation in this case. (C) 2017 Elsevier B.V. All rights reserved.