Monitoring of Yeast Cell Volume Changes Using Electrical Impedance Spectroscopy

Electrical impedance spectroscopy (EIS) offers a noninvasive mean to probe the physiological and morphological dynamics of microbial populations. Here, we present an impedance-based circuit modeling approach to characterize and monitor the volumetric and electrical behavior of Saccharomyces cerevisiae across its growth cycle. By modeling the yeast suspension as a dielectric system and fitting its frequency-dependent impedance to a modified Randles circuit, we extract discrete electrical parameters—capacitance, resistance, and diffusion elements—that reflect cellular properties and concentration. We show that suspension capacitance scales linearly with optical density (OD) and correlates with estimated yeast cell volume, enabling direct quantification of biomass without requiring optical dilution. This relationship holds across dilution series and growth kinetics experiments, where temporal increases in capacitance mirror population expansion. Furthermore, metabolic activity within the media is captured through shifts in background capacitance, providing insights into nutrient consumption and media composition. Our method offers a scalable, label-free platform for real-time yeast monitoring, with broad implications for bioprocess optimization, synthetic biology, and intelligent bioreactor design.