26. Yeast stress when fermenting at high gravity—Sources, damage and the cellular response
Chris Powell (1); (1) University of Nottingham, Nottingham, U.K.
Technical Session 8: Yeast Stress & Performance
Monday, August 15 • 8:15–9:30 a.m.
Tower Building, Majestic Level, Majestic Ballroom
Very high-gravity (VHG) fermentations >20°P are increasingly
employed within the brewing industry to maximize process efficiency.
However, it is known that the use of VHG worts can create issues during
fermentation, particularly with regard to achieving the desired final
product specifications. From the perspective of the yeast culture, the
environment of VHG wort is considerably different from that of standard
worts, and this can impact the health and function of the population.
The resulting detrimental effects can include longer fermentation times,
altered flavor characteristics and, in some instances, incomplete or
inefficient conversion of sugars to ethanol. Many of these artifacts are
related to yeast health and it is accepted that VHG conditions place
increased stress on yeast. However, little is known regarding the
precise character and intensity of these stress factors and their direct
effects on individual cells. Here we characterize the wort environment
with regard to potential for oxidative and osmotic stresses and describe
the impact of these factors on yeast physiology, DNA integrity and
organelle damage. In addition, the relationship between initial wort
gravity, fermentation progression and the promotion of intracellular
anti-stress mechanisms involved in cell homeostasis and repair will be
discussed. It is anticipated that the data generated and presented here
will provide insight into some of the challenges faced by yeast in
fermenting worts of particularly high sugar concentration, as well as
potential mechanisms for alleviating stress.
Chris Powell holds a Ph.D. degree on yeast cellular aging and
fermentation performance from Oxford Brookes University, UK (2001).
After a postdoctoral research position at the same institute
investigating rapid methods for detection of contaminants in beer
(2001-2004) he worked in the Research Department for Lallemand Inc.,
Montreal, Canada (2004-1010), ultimately occupying the positions of
senior scientist in brewing and project manager in genetic
identification. In 2010 Chris moved to the University of Nottingham,
where he is currently a lecturer in yeast and fermentation. His core
subject areas include yeast physiology and fermentation biotechnology,
particularly related to the brewing, beverage and sustainable bioenergy
sectors. Chris is the author or co-author of more than 40 publications
and a regular reviewer for several scientific journals. He has
previously served as chair of the ASBC Technical Committee and has held a
position on the ASBC Board of Directors since 2010, currently acting as