Program Book - Master Brewers Association of the Americas

O-58
Gene expression analysis of lager brewing yeast during
propagation process using newly developed DNA microarray
TOMOKO SHIMONAGA (1), Susumu Furukubo (1), Nobuyuki
Fukui (1)
(1) Process Development Department, Engineering & Process
Development Division, Suntory Ltd., Osaka, Japan
During propagation and fermentation processes in brewing,
problems derived from yeast behavior sometimes happen, and so
many efforts have been made to solve them. However, it is quite
difficult to figure out the critical factors that cause them because
yeast metabolism is often considered a sort of “black box”. We have
completed the whole genome sequence analysis of a representative
brewing yeast, Saccharomyces pastorianus Weihenstephan Nr. 34. It
enabled us to confirm a complicated chromosomal structure in detail
and to find the genes specific to lager brewing yeast. Furthermore,
a newly developed DNA microarray (LBYG array; based on lager
brewing yeast genome) provided comprehensive analysis of
gene expression and offered some explanations of characteristic
sulfite production during fermentation (Nakao, Y., et al., Proc.
Eur. Brew. Conv., Venice, 2007, 14 pp.). Here we show ability of
microarray analysis for practical brewing processes. “Elongation”
is observed as yeast morphological changes to pseudohyphal form
during yeast propagation or the fermentation process. When it
occurs, yeast growth rate tends to decline, and it requires a longer
fermentation time that can deteriorate beer quality. In this study,
gene expression analysis using the DNA microarray was carried
out during propagation to reveal the mechanism of “elongation”
at the molecular level and finally establish the optimum condition.
Among various brewing factors, aeration was proved to be the most
important factor in “elongation”, so both normal and elongated
yeasts obtained from different aeration conditions in propagation
were subjected to gene expression analysis. The resultant gene
expression profiles were compared with each other in each biological
pathway according to SGD (Saccharomyces Genome Database,
Stanford Univ.). Consequently, elongated yeast showed significantly
lower gene expression in ergosterol biosynthesis. The number of
elongated yeast during propagation was dramatically decreased by
addition of ergosterol itself and its intermediate, mevaloate and
pantothenate, which is a coenzyme for rate-limiting reaction of this
pathway, which supports a hypothesis that lack of ergosterol was the
trigger of elongation.
Tomoko Shimonaga received a M.S. degree in engineering from
Osaka University, majoring in biotechnology. In April 2002, she
began employment with Suntory as a researcher in the Institute for
Advanced Technology. She was involved in fundamental research
on yeast genetics and physiology and worked as a member of the
lager brewing yeast genome research group. Since April 2006, she
has served in the Engineering & Process Development Division and
engaged in practical beer brewing, in particular yeast propagation
and fermentation processes.
94
O-59
The role of the yeast vacuole during fermentation
KATHERINE SMART (1)
(1) University of Nottingham, Loughborough, United Kingdom
The vacuole of brewing yeast can occupy as much as 25% of the total
intracellular volume. The vacuolar cytoplasm (lumen) is bounded
by a membrane (tonoplast), but the structure formed is a totally
dynamic organelle with a tendency to coalesce and fragment in
response to both environmental stimuli and the physiological status
of the cell. One of the reasons for this dynamism is the numerous
roles this organelle plays, including maintaining pH and ion
status; macromolecule degradation and salvage; protein turnover;
osmoregulation; volume regulation; the storage of amino acids,
carboxylic acids, carbohydrates and vitamins; and the sequestration
of toxins. The morphological changes that occur during pitching
and fermentation will be demonstrated. In an attempt to elucidate
the rationale for this dynamism during fermentation, this
presentation will focus on specific functions of the organelle.
Recently the proteins associated with the vacuolar lumen have been
identified in laboratory strains using proteomics technologies.
Using this as a guide, the expression of the genes that encode
these proteins during laboratory and full scale lager fermentations
will be discussed in the context of fermentation progression and
performance.
Katherine Smart completed a B.S. (Hon.) degree in biological sciences
at Nottingham University and was awarded the Rainbow Research
Scholarship to complete a Ph.D. degree in brewing yeast physiology
at Bass Brewers. She held a research fellowship at Cambridge
University and academic posts at Oxford Brookes University before
joining the University of Nottingham in 2005 as the SABMiller
Professor of Brewing Science. Katherine has received several awards
for her research: the IBD Cambridge Prize (1999), the prestigious
Royal Society Industrial Fellowship (2001–2003) and the Save
British Science Award (2003). She has published more than 80
papers, book chapters, and proceedings.