The estimation of the yeast growth phase by nonlinear dielectric properties of the measured electric current

We measured the activity of yeast in each growth phase by using nonlinear d ielectric properties. In this paper, we used a 2-electrode system, rather t han the previous 4-electrode system, to measure the current waves for the a nalysis of the phase angle of response waves and the facilitation of the me asurements. As a result, in the exciting frequency and field, 14 Hz and 0.7 5 V cm or 1.25 V cm(-1), the 2nd harmonic of the response wave for cell sus pensions showed a significant difference between the induction phase and th e others. However, for the supernatant of suspensions, there was no differe nce in the power spectrum of the even-numbered harmonics. With the phase an gle, the same tendency was observed in the power spectrum. When another com bination of field and frequency (0.25 or 1.75 V cm(-1) and 7, 28, 35 or 42 Hz) was applied, there were no significant differences in either the power spectrum or the phase angle. These results were different from those measur ed by a 4-electrode system, although the range of frequency and field are a lmost the same. However, we found that the 2nd harmonics in the induction p hase were different from those in the other phases. We can say that this 2- electrode system is applicable for the estimation of the growth of yeast ce lls. (C) 2001 Elsevier Science B.V. All rights reserved.