Yeast and Fermentation Session
Chris D Powell, The University of Nottingham, UK
Co-author(s): Tobias Fischborn, Lallemand Inc., Canada
ABSTRACT: Saccharomyces pastorianus strains are natural hybrids of S. cerevisiae and S. bayanus
yeast and display properties particularly suited to the production of
lager type beers. While it is accepted that lager strains arose
approximately 200 years ago following a mating reaction between these
two species, recent evidence has suggested that such an event may have
occurred more than once in the evolution of this yeast. It has been
suggested that the S. pastorianus species may contain two
subgroups, designated Saaz (Group 1) and Frohberg (Group 2), as a result
of separate mating events. These groups have been broadly
differentiated according to a number of criteria including genome
rearrangements, gene copy number, DNA sequence polymorphisms, and
differences in ploidy. Despite detailed genetic analysis, only limited
studies have previously been performed to characterize their phenotypic
properties. The purpose of this study was to investigate the
similarities and differences between the physiological characteristics
of Saaz (Group 1) and Frohberg (Group 2) yeast. A number of strains
belonging to each group were selected and assessed for their growth
characteristics and their capacity to assimilate sugars. Furthermore,
each strain was analyzed for its ability to withstand stress factors
associated with the production of alcoholic beverages, including
temperature and osmotic and oxidative stress. The data obtained and
presented here indicate that there are some fundamental differences
between the capacity of each yeast group to respond to their immediate
environment. While this is particularly interesting for the
understanding of lager brewing yeast strain variation, it may also be
significant for associated industries such as the biofuel industry,
where investigation into the properties of industrial yeast strains is
of particular importance, or the active dried yeast industry, where
robust brewing yeast strains are required to withstand stress factors
associated with desiccation, in addition to favorable properties during
fermentation.
Chris Powell holds a Ph.D. degree on the subject
of yeast cellular aging and fermentation performance from Oxford Brookes
University, U.K. Chris has also occupied research positions at Bass
Brewers (now Coors UK) and more recently at Lallemand, based in
Montreal, Canada. During his six years at Lallemand, Chris was
responsible for the R&D laboratory for the molecular identification
and characterization of micro-organisms utilized within the food and
beverage industries, in addition to research focused on brewing yeast.
In 2010 Chris returned to the United Kingdom to take up his current
position as lecturer in yeast and fermentation at the University of
Nottingham. Chris is presently involved in research in the areas of both
brewing science and sustainable bioenergy. Chris is the author or
co-author of more than 40 scientific publications and is a regular
reviewer for several scientific journals. Chris has also served on the
ASBC Technical Committee since 2005 and the ASBC Board of Directors
since 2010. Outside of work, Chris is a keen soccer player and spends a
significant portion of his time running, hiking, and exploring different
parts of the world.
