A study of the effect of calcium chloride (CaCl₂) and pH on the flocculation ability of Saccharomyces cerevisiae (NCYC 1195)

The best fermentation ability of yeast-forming flock species is highly desirable in the bioethanol production process. Saccharomyces cerevisiae NCYC 1195 is known to have the ability to form flock which is influenced by the concentration of calcium chloride (CaCl₂) and pH. This is because calcium ions can form bonds with mannose on the surface of the cell wall of S. cerevisiae, while the degree of acidity will affect the charges of specific protein on the cell wall. The ability of flocculation will precipitate S. cerevisiae cells so that they will not be mixed with fermentation medium. Thus, the separation process of cell and fermentation media can be done quickly and efficiently, without expensive centrifugation step. The aim of this study was to determine the effect of CaCl₂ concentration and pH that used to determine the ability and stability of the flock of S. cerevisiae. Three concentration of CaCl₂ (10^-5, 10^-7, 10^-9 M) were used as well as three variations of pH (4,5,6). Culture was incubated at 30°C with 100 rpm agitation and analysed for flocculation ability every 4 hours during 24 hours. The stability of the flock was analysed every 24 hours during 30 days. The highest flock formation ability (73.15%) was obtained with the concentration of CaCl₂ concentration 10^-9 M and pH 5.