Clarification of small volume microbial suspensions in an ultrasonic standing wave

Abstract

The removal of Saccharomyces cerevisiae and Escherichia coli from 2.5 ml suspensions in ultrasonic standing wave formed at 1 or 3 MHz has been characterized. The standing wave was set up by a plane transducer and reflector mounted in the vertical plane. Cells in the ultrasonic field first concentrated in vertical planes at half wavelength separations. The ultrasound was then pulsed to allow clumps of concentrated cells to sediment in a controlled way during the short 'off' intervals. Yeast removal from suspension at a concentration of 3 x 10(9) ml-1 (14% volume v/v) was 99.5% in a total time of 4.5 min. Almost total (99.5%) clarification of prokaryote (E. coli) suspension was achieved here for the first time in a standing wave field. The clarification of a 1.3 x 10(11) ml-1 (16% v/v) E. coli suspension occurred over 11.5 min. The period decreased to 7 min in the presence of a polycationic flocculant, polyethyleneimine. The implications of the results for design of systems to further reduce clarification times are discussed. Removal efficiency for both S. cerevisiae and E. coli decreased with decrease in cell concentration. This concentration dependence is shown not to be simply a consequence of acoustic interaction between single cells. Flow cytometry of stained cells detected no loss of cell viability arising from the ultrasonic procedure.

Acoustofluidics 23: acoustic manipulation combined with other force fields

“…In this way the perfusion flow can be maintained without loss of the reactor contents. Similar modes of operation can be found in a range of other work 29,30 .…”

Influence of biomass, throughput and true electric power input on the separation efficiency of a 60 mL acoustic filter

“…One utilisation of particle manipulation by ultrasonic radiation which has been developed during the last decade up to successful application in industrial environments is the Ultrasonically Enhanced Settling (U.E.S.) for filtration purposes (Grö schl, 1998;Limaye, 1998;Trampler, 1999;Gorenflo, 2005;Dalm, 2005).…”

Microfluidic bio-particle manipulation for biotechnology

“…However, in some high throughput studies with PDMS materials, it can go up to 10 W [97] which requires an additional external cooling of the piezoelectric material and the channel. The use of aluminum block as a heat sink may be applied [85,97,110].…”

“…Cell viability has also been assessed after acoustic separation or manipulation processes. In order to determine the viability of bio-particles, trypan blue was used, and it was observed that the cells were not negatively affected from acoustic manipulation process [81,86,92,110] as they were viable after being exposed to ultrasonic waves. Referring to the strong suits of the ACT methods, an ACT diagnosis device has already commercialized (Attune Acoustic Focusing Cytometer by Life Sciences, www.lifetechnologies.com).…”