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Vorträge und Posterpräsentationen (mit Tagungsband-Eintrag):

C. Koch, S. Radel, M. Gröschl, E. Benes:
"Effect of ultrasonic plane wave fields on yeast cultures";
Vortrag: ICU 2009 - International Congress on Ultrasonics, Universidad de Santiago de Chile, Santiago/Chile; 11.01.2009 - 17.01.2009; in: "ICU 2009 - International Congress on Ultrasonics - Book of Abstracts", (2009), S. 268.



Kurzfassung englisch:
In this work yeast cell suspensions were filtered using a so-called "h-shape" filter. This set-up is a continuous throughput filter, using an ultrasonic standing wave field to "guide" the suspended particles to one of the two outlets. Thus one can harvest an enriched suspension from one outlet and the cleared fluid from the other. Apart from getting experimental results for the separation efficiency to compare to simulations done using FLUENT, we wanted to see the effect of passing through several pressure nodal and anti-nodal planes on the yeast cells. Especially cells found in the filtrate should show possible effects of stress induced by the pressure differences.
Yeast cells (Saccharomyces cerevisiae) were suspended in phosphate buffered saline to a final concentration of around 3,5*10^6 cells/mL and a peristaltic pump was used to feed the resonator at a throughput of 14 L/day in accordance with the simulations. The transducer was driven at a resonance frequency of around 2,2 MHz at a true electrical power input of 3 W. Haemocytometer counts were used to measure the cell concentrations and, at the same time, cell viability by methylene blue staining. To monitor cell wall integrity we determined the UV optical density (O.D.) of the supernatant at 260 nm which is a measure for protein content of the supernatant. The cells´ ability to reproduce was assessed by plate counts, determining the percentage of colony forming units (CFUs).
The performance of the filter was not very reliable, clump-formation turned out to be a drawback on separation efficiency. In order to avoid this, a higher throughput velocity was tested resulting in more turbulent and less reliable behavior of the filter. Separation efficiencies were found to be 53 +/- 18 %, corresponding to no effect of the ultrasound acting as "rails" at all. Cell viability was not influenced significantly by the separation process compared to unsonicated controls. However, the O.D. of the samples taken from both outlets (cleared and enriched) showed a slight but significant increase compared to the controls. Plate counts showed such a great variance that more experiments are currently under way.\

Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.