Detection of proteinases in Saccharomyces cerevisiae by flow cytometry

• Published in: Journal of the Institute of Brewing Vol. 111; no. 1; pp. 26 - 32
• Main Authors: Hutter, K.J, Miedl, M, Kuhmann, B, Nitzsche, F, Bryce, J.H, Stewart, G.G
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 2005; Institute of Brewing
• Subjects: Autolysis; beer quality; Beers; Biological and medical sciences; brewers yeast; fermentation performance; Fermented food industries; flow cytometry; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; industrial yeast strains; Methods of analysis, processing and quality control, regulation, standards; proteinase activity; proteinases; Flow cytometry; Yeast; proteinase activity; Strain; Fungi; Autolysis; Analysis method; Ascomycetes; Control method; industrial yeast strains; Detection; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0046-9750; 2050-0416
• DOI: 10.1002/j.2050-0416.2005.tb00645.x

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.