Nonlinear Dielectric Properties of Yeast Cells Cultured in Different Environment Conditions

摘要

The harmonics of an electric current passing through a yeast suspension exh bit particular patterns according to the biological activity of the. cells, constituting the nonlinear dielectric response of yeast cells, and the measurement of these patterns is a technique for determining the activity of living cells. The concentrations of glucose and oxygen in yeast culture medium influence whether fermentation or respiration of the yeast cells occurs. Measurements were made with yeast cells (Saccharomyces cerevislae) cultured aerobically and anaerobically at sufficient glucose concentrations (aerobic and anaerobic fermentation), and also under aerobic conditions at a limited glucose concentration (respiration). The results showed that the harmonics were barely detectable for yeast cells in aerobic fermentation and respiration, but that cells in anaerobic fermentation produced substantial third and fifth harmonics. It is inferred that environmental conditions affect yeast cells' nonlinear dielectric response; furthermore, it appears that measurement of these nonlinear properties may be an effective means of determining the activity of yeast cells adjusted to the conditions of their cultivation.