Using dielectrophoretic spectra to identify and separate viable yeast cells

Area of Science:

• Biophysics
• Biotechnology
• Food Science

Background:

• Assessing yeast cell viability is crucial for the fermentation and brewery industries.
• Traditional methods can be time-consuming and may not offer real-time analysis.
• Dielectrophoresis (DEP) presents a potential non-invasive method for cell analysis.

Purpose of the Study:

• To investigate the use of dielectrophoresis for distinguishing between viable and non-viable yeast cells.
• To analyze the dielectric properties of yeast cells to determine viability.
• To evaluate the potential of DEP for cell separation in industrial fermentation.

Main Methods:

• Yeast cells (Saccharomyces cerevisiae) were subjected to non-uniform sinusoidal electric fields using micro-parallel cylindrical electrodes.
• Cell viability was assessed by analyzing dielectrophoretic spectra and lower critical frequencies (LCF) at varying medium conductivities.
• Real-time image processing and a sequential signal generator (SSG) were used to monitor cell movement and collection yield.

Main Results:

• Living and dead yeast cells exhibited distinct dielectrophoretic spectra and dielectric properties.
• The cytoplasmic conductivity (σc) of living yeast cells was approximately 0.2 S m⁻¹, significantly higher than that of dead cells (≤ 0.05 S m⁻¹).
• Positive dielectrophoresis (pDEP) was observed, with LCF values shifting based on medium conductivity.

Conclusions:

• Dielectrophoresis is a viable method for differentiating and separating viable from non-viable yeast cells.
• Cellular dielectric properties, particularly cytoplasmic conductivity, serve as reliable indicators of yeast cell viability and metabolic health.
• This technique offers a scalable and real-time approach for quality control in the fermentation industry.