Flotation Assay in Small Volumes of Yeast Cultures

Flocculation is a naturally occurring process of reversible aggregation (cell-cell aggregation) of yeast cells (1 ), whereas flotation is defined as microbial enrichment in foams (2 ), which can be carried out either by induced flotation (with addition of flotation agents) or spontaneous flotation (without addition of flotation agents). The spontaneous flotation of Saccharomyces cerevisiae was first described in 1991 by Gehle et al. (3 ), who correlated flotation with the ability of the strain DSM 2155 to form cell aggregates. In 1996, Palmieri and collaborators (4 ) showed that flocculation and flotation were separate phenomena, by studying a new floating strain of Saccharomyces cerevisiae , which was highly hydrophobic but not flocculant. Batch flotation has been used by a number of authors for the separation of yeast cells (4 ,5 ), bacteria (6 ), algae (7 ), bacterial spores, vegetative cells (8 ), recovery of minerals, coal and crude petroleum (9 ), deinking recycled pulp paper and de-oiling water (10 ,11 ).