Detection of Proteinases in Saccharomyces cerevisiae by Flow Cytometry
Karl-Josef Hutter1, Michaela Miedl2 , Britta Kuhmann1, Frank Nitzsche3 , James H. Bryce2 and Graham G. Stewart2 ,4
1 Eichbaum Brauereien AG, Käfertaler Straße 170, D-68163 Mannheim, Germany.
2 ICBD, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, United Kingdom.
3 Koenig Brauerei, Friedrich-Ebert-Str. 255-263, D-47139 Duisburg, Germany.
4 Corresponding author. E-mail: G.G.Stewart@hw.ac.uk
J. Inst. Brew. 111(1), 26-32, 2005 | VIEW ARTICLE
ABSTRACT
The physiological state of a yeast population used for inoculation determines how rapidly the cells adapt to new environmental conditions, begin proliferating and utilising extract. The decision as to whether a yeast culture is suitable for re-pitching should not be based only on viability determinations since this can be misleading. Increased proteolytic activity in a yeast population indicates the onset of senescence. A flow cytometric method has been developed for measuring a wide variety of proteinases in Saccharomyces cerevisiae employing a commercially available casein-dye conjugate. The detection of intracellular proteinase activity gives an early indication of apoptotic events and allows improved assessment of the physiological state of a yeast population. This knowledge will assist the industry to optimize the selection of yeast and its subsequent fermentation performance. Yeast cell autolysis with all its negative consequences for beer quality and stability will thus be minimised.
Key words:
Autolysis, flow cytometry, industrial yeast strains, proteinase activity.
Publication no. G-2005-0322-262 ©2005 The Institute & Guild of Brewing