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Advisor(s)
Abstract(s)
Flocculation is an eco-friendly process of cell
separation, which has been traditionally exploited by the
brewing industry. Cell surface charge (CSC), cell surface
hydrophobicity (CSH) and the presence of active flocculins,
during the growth of two (NCYC 1195 and NCYC 1214)
ale brewing flocculent strains, belonging to the NewFlo
phenotype, were examined. Ale strains, in exponential
phase of growth, were not flocculent and did not present
active flocculent lectins on the cell surface; in contrast, the
same strains, in stationary phase of growth, were highly
flocculent (>98%) and presented a hydrophobicity of
approximately three to seven times higher than in exponential
phase. No relationship between growth phase,
flocculation and CSC was observed. For comparative
purposes, a constitutively flocculent strain (S646-1B) and
its isogenic non-flocculent strain (S646-8D) were also used.
The treatment of ale brewing and S646-1B strains with
pronase E originated a loss of flocculation and a strong
reduction of CSH; S646-1B pronase E-treated cells displayed
a similar CSH as the non-treated S646-8D cells. The
treatment of the S646-8D strain with protease did not
reduce CSH. In conclusion, the increase of CSH observed
at the onset of flocculation of ale strains is a consequence of
the presence of flocculins on the yeast cell surface and not
the cause of yeast flocculation. CSH and CSC play a minor
role in the auto-aggregation of the ale strains since the
degree of flocculation is defined, primarily, by the presence
of active flocculins on the yeast cell wall.
Description
Keywords
Brewing yeast Cell–cell adhesion Cell surface charge Flocculation Flo proteins Hydrophobicity
Citation
Publisher
Springer Verlag