Impact of zinc on yeast membranes and cell physiology during brewing fermentations

De Nicola, R. and Anthony, Sarsha and Walker, G. and Learmonth, R. (2005) Impact of zinc on yeast membranes and cell physiology during brewing fermentations. In: XXIVth International Specialised Symposium on Yeasts, 28 Sep - 02 Oct 2005, Castellon, Spain.


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[Abstract]: Yeasts require a range of metals for optimal growth, metabolism and fermentation
performance. In production of fermented beverages, zinc is of prime importance, with
levels of at least 0.3 ppm preferable for optimal fermentation and avoidance of stuck
ferments. Zinc is a co-factor for numerous important biosynthetic and metabolic
enzymes including, significantly, various glycolytic enzymes and alcohol
dehydrogenase. In addition it plays critical regulatory roles through the action of Znfinger
DNA binding proteins, and affects yeast-yeast flocculation. Zinc is also known
to modulate yeast stress responses, mainly due to its role as a co-factor for the
antioxidant enzyme superoxide dismutase. Furthermore, zinc ions are thought to have
some effects on stability and dynamics of cell membranes, which may lead to
downstream effects on cell permeability and signalling systems. In brewing
fermentations, zinc is actively assimilated by yeast from malt wort. However, in some
instances its bioavailability may be limiting due to decrease of zinc levels during
mashing, lautering and boiling through complexing in precipitated trub. Consequently
low zinc levels in wort may lead to slow and incomplete fermentations.
We have studied the impact of varying zinc levels in a model brewing situation,
utilising a wort medium initially depleted of zinc. The zinc was depleted by
biochelation using yeast cells, providing a wort normal in all aspects except zinc
levels. A brewer's strain of Saccharomyces cerevisiae was extensively cultured in
low zinc medium to deplete cellular zinc levels, and then pitched into worts
containing zinc concentrations ranging from 0 to 10 ppm (provided as zinc acetate).
In addition to growth and fermentation parameters we assessed membrane fluidity by
measuring Generalized Polarization of the membrane-localising fluorescent probe
laurdan (6-lauroyl-2-dimethylamino naphthalene). We observed that zinc levels
impacted upon growth rate, ethanol yields and membrane fluidity. The membrane
fluidity varied with culture age and ethanol accumulation, as well as in relation to
cellular zinc levels. Results will be discussed with reference to the impact of zinc on
brewing yeast fermentation performance and stress physiology.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: Conference publication consists of only the abstracts of papers presented at the conference. Abstract only posted here.
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 11 Oct 2007 00:29
Last Modified: 02 Jul 2013 22:34
Uncontrolled Keywords: zinc, yeast membranes, cell physiology, brewing, fermentation
Fields of Research : 06 Biological Sciences > 0601 Biochemistry and Cell Biology > 060199 Biochemistry and Cell Biology not elsewhere classified
10 Technology > 1003 Industrial Biotechnology > 100303 Fermentation

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