Pb 2+ Inhibits Competitively Flocculation of Saccharomyces cerevisiae
Cláudia Gouveia 1, and Eduardo V. Soares 2, 3
1 CIEA, Instituto Superior de Engenharia do Instituto Politécnico do
Porto, Rua Dr António Bernardino de Almeida, 431, P-4200-072
Porto, Portugal.
2 CIEA-Departamento de Engenharia Química, Instituto Superior de
Engenharia do Instituto Politécnico do Porto, Rua Dr António Bernardino
de Almeida, 431, P-4200-072 Porto, Portugal.
3 Corresponding author. E-mail: evs@isep.ipp.pt
J. Inst. Brew. 110(2), 141-145, 2004 | VIEW ARTICLE
ABSTRACT
Pb 2+ inhibited calcium-induced
flocculation in Flo1 (S646-1B) and NewFlo phenotype strains
(NCYC 1190, NCYC 1195 and NCYC 1364) of Saccharomyces cerevisiae.
Flocculation was restored after washing with water or EDTA,
which suggests a reversible binding of Pb 2+
to yeast cell walls. Pb 2+
probably inhibited flocculation by competing with Ca 2+,
since Pb 2+ inhibition was
alleviated by excess of Ca 2+.
Using a fluorescent avidinfluorescein isothiocyanate (Avidin-FITC)
probe, active cell surface flocculation lectins, in the presence
of Ca 2+ ions, were visualized.
Conversely, Avidin-FITC was not fixed to yeast walls of flocculent
cells, in the presence of Pb 2+
ions or in the simultaneous presence of 0.05 mM Ca 2+
and 0.4 mM Pb 2+. These results
suggest that Pb 2+ ions were
not able to induce the correct conformation of the lectin-like
component and reinforces the hypothesis that Pb 2+
ions compete for the same "calcium site" of flocculation zymolectins.
Key words:
Brewing yeast, calcium, flocculation inhibition,
Flo1 phenotype, lead, NewFlo phenotype.
Publication no. G-2004-0521-224 ©2004 The Institute & Guild of Brewing