[Zurück]

C. Koch, S. Radel, M. Gröschl, E. Benes, W.T. Coakley:
"Effects of ultrasonic plane wave fields on yeast cultures";
Vortrag: 3rd Congress of the Alps Adria Acoustics Association, Hotel Weitzer, Graz; 27.09.2007; in: "3rd Congress of the Alps Adria Acoustics Association, Hrsg: Joanneum Research", (2007), 4 S.

We investigated the effect of 2,3 MHz ultrasonic plane wave fields on yeast cells (Saccharomyces cerevisiae
or baker's yeast) suspended in saline and saline/ethanol mixtures. When suspended in saline, the yeast cells
agglomerated at the pressure nodal planes and methylene blue counts showed no increase in cell death compared to
control groups. Suspensions of yeast in saline/ethanol mixtures showed a different behavior: the stable alignment of the
cells in the pressure nodal planes broke down and the cells were turbulently driven through the resonator. The absence
of free radicals (measured by iodine from KI cleavage) in the medium indicated that inertial cavitation did not occur.
Still methylene blue counts showed a decrease in cell viability. The attempt to eliminate the gas bubbles during
sonication was motivated by the additional stress-factor they may represent to the cells. Although cavitation was not
observed the surface of the gas bubbles represented obstacles to the moving yeast. Preliminary tests showed that in
case of gas-free liquids a higher concentration of EtOH had to be present to initiate the turbulent behaviour. Therefore
the suspension for this experiment was additionally degassed after preparation by exposure to an under-pressure of 20
kPa for 10 minutes.

ultrasound, plane wave field, yeast, non-cavitational