COMPARISON OF THE CONTINUOUS FLOTATION PERFORMANCES OF SACCHAROMYCES-CEREVISIAE LBG H620 AND DSM-2155 STRAINS

Saccharomyces cerevisiae LBG H620 and DSM 2155 strains were continuous ly cultivated under carbon (C)-limited, phosphorus (P)-limited and nit rogen (N)-limited growth conditions. Cell and protein concentrations i n feed, foam, and residue as well as the degree of cell recovery and t he rate of foaming were measured, and the concentration and enrichment factors were evaluated at different dilution rates (D). The LBG H620 cells were reduced, while the DSM 2155 cells were enriched in the foam . The highest concentration factors in DSM 2155 cells were attained if they were cultivated under strong P-limitation at a low D. Fairly hig h concentration factors were also found under C-limitation. Under N-li mitation, low concentration factors were found with low Ds. At the beg inning of the continuous cultivations, all of the cells were recovered , but with advancing time the degree of recovery and cell concentratio n and the enrichment factor ratio diminished. The cellular properties of the yeast were characterized by flow cytometry, and the surface pro perties by measurements of their hydrophobicity, electrophoretic mobil ity, and chemical composition (using X-ray photoelectron spectroscopy, XPS). These investigations indicated that the large difference in flo tation between the two strains is due to different surface properties. Strain DSM 2155 has higher surface hydrophobicity and lower electroki netic potential. Cell wall properties and the cell flotation depend on medium composition and age of the culture.