The permittistat: a novel type of turbidostat

Abstract

Baker's yeast was grown in a novel type of turbidostat in which the steady-state biomass level was controlled not by the optical turbidity but by the dielectric permittivity of the suspension at appropriate radio frequencies. Dry weight, fresh weight, the optical density at 600 nm, percentage viability (from methylene blue staining), bud count and ethanol concentration were measured off-line and the cell size distribution was recorded using flow cytometry. Any changes in the physiological properties of the yeast had a negligible effect on the ratio between the permittivity set (and measured) and the steady-state dry weight, fresh weight or optical density of the cultures. The permittistat was found to provide an extremely convenient means for carrying out turbidostatic culture.

Control of metabolite efflux in microbial cell factories: current advances and future prospects

“…[180,181]). In conclusion, as ever in biology, evolutionary considerations can give useful insights into circumstances in which the secretion of a biosynthesised metabolite is, perhaps surprisingly, beneficial for the host.…”

Analysis of a continuous-culture technique for the selection of mutants tolerant to extreme environmental stress

“…The implementation shown in Figure 5 is more complicated than BOICS in that it requires the control of two pumps, but it may turn out to have other advantages. In view of the above discussion, the CO 2 -stat could be replaced by a turbidostat, pHauxostat (Martin and Hempfling, 1976;Schulthess et al, 1990), permittistat (Markx et al, 1991), or nutristat (Kleman et al, 1991;Mori et al, 1983). In the latter case, a nutrient concentration is directly measured and controlled.…”

On-Line, Real-Time Measurements of Cellular Biomass using Dielectric Spectroscopy

“…The Biomass Monitor has also found a significant niche in fermentation process control (Kronlof, 1990;Kronlof, 1991;Markx et al, 1991b;Austin et al, 1994;Davey et al, 1996). Markx et al (1991b) grew bakers yeast in a novel type of turbidostat; or more correctly permittistat, in which a constant biomass level was continuously maintained by a feedback mechanism based upon the dielectric permittivity of the culture.…”

“…Markx et al (1991b) grew bakers yeast in a novel type of turbidostat; or more correctly permittistat, in which a constant biomass level was continuously maintained by a feedback mechanism based upon the dielectric permittivity of the culture. Dielectric biomass estimations were made using the two frequency method at 0.4MHz and 9.5MHz.…”