SEPARATION OF VIABLE AND NONVIABLE YEAST USING DIELECTROPHORESIS

Dielectrophoresis, the movement of particles in non-uniform AC electri c fields, was used to rapidly separate viable and non-viable yeast cel ls with good efficiency. Known mixtures of viable and heat-treated cel ls of Saccharomyces cerevisiae were separated and selectively isolated using positive and negative dielectrophoretic forces generated by mic roelectrodes in a small chamber. Good correlations with the initial kn own relative compositions were obtained by direct microscopic counting of cells at the electrodes after initial dielectrophoretic separation (r = 0.995), from methylene blue staining (r = 0.992) and by optical absorption measurements (r = 0.980) of the effluent after selectively flushing out the viable and non-viable cells from the chamber. Through measurement of cell viability by staining with methylene blue and pla te counts, for an initial suspension of approx. 1.4 x 10(7) cells per ml containing 60% non-viable cells, the dielectrophoretically separate d non-viable fraction contained 3% viable cells and the viable fractio n 8% dead cells. The separation efficiency is increased by dilution of the initial suspension or by repeat operation(s). Cell viability was not affected by the separation procedure.