Program Book - Master Brewers Association of the Americas

P-133
Yeast lag phase tracking: A toolkit for fermentation
performance prediction
KATHERINE MILLER (1), Chris Boulton (1), Wendy Box (1),
Katherine Smart (1)
(1) University of Nottingham, Sutton Bonington Campus,
Loughborough, United Kingdom
Consistency of fermentation duration is a key issue for the brewing
industry, particularly for fermentations that use freshly propagated
yeast. It is generally accepted that lag phase can contribute
considerable variation to total fermentor residence time. Variability
of lag phase duration can be attributed to several factors, including
generation number of the yeast, batch to batch differences in wort
composition, fermentor physical environment and rate of yeast
dispersal within the fermentor. Lag phase may be defined as the time
required to progress from pitching to initial bud emergence. In this
presentation, predictive biomarkers of lag phase progression will
be identified that permit variations in this parameter to be rapidly
detected, including DNA synthesis by flow cytometry; the expression
of SPG1, CHS2 and CHS3 by real time PCR; and fluorescent
tagging of key cellular events using confocal microscopy. Together,
these biomarkers constitute a toolkit for predictive fermentation
performance analysis. The potential of this during laboratory
(2 l) and full (3275 hl) scale fermentations will be demonstrated. It is
suggested that this toolkit will permit the development of effective
process control, enabling more consistent yeast performance after
pitching.
Katherine Miller is in her third year of an Engineering and Physical
Sciences Research Council industrial studentship cosponsored
by Coors Brewers Limited. She is working at the University of
Nottingham under the supervision of Professors Katherine Smart
and Chris Boulton. The aim of her Ph.D. project is to investigate the
achievement of consistent onset of fermentation in cylindroconical
fermentors. Katherine graduated from the University of Sheffield
in 2005 with a master of biological sciences degree in biochemistry.
This involved carrying out a research project on the role of the actin
cytoskeleton in apoptosis in Saccharomyces cerevisiae.
P-134
The effect of varying dissolved oxygen levels in wort on yeast
fermentation performance in craft breweries
NEVA PARKER (1), Troels Prahl (1), Chris White (1)
(1) White Labs, Inc., San Diego, CA
Proper levels of oxygen have proved a necessity for yeast during
the early stages of wort fermentation, as it plays an integral role
in promoting lipid synthesis for cell wall production. Without an
adequate supply of this building block, yeast cells characteristically
display low viability and poor performance in fermentation.
Recommended levels of oxygenation are in the range of 8–10
ppm; however, many craft breweries depend on existing protocols
that do not involve measurements and may not be optimal. An
investigation is described here that explores the adequacy of
current dissolved oxygen levels in craft breweries and whether
this has any correlation with fermentation issues, such as long lag
time and slow fermentations. The range of oxygenation levels with
respect to their effects on fermentation speed and the variance in
dissolved oxygen requirements between laboratory grown cultures
and multiple generation brewery cultures are also addressed. The
dissolved oxygen levels of wort from a small sampling of mid-sized
craft breweries were compared to the same wort at a measured 10
ppm in lab-scale fermentation trials. A commercial ale yeast strain
was used for all fermentations, and fermentation vessels were kept at
a constant temperature in a glycol-controlled water bath. The study
is designed to determine whether craft breweries are sufficiently
oxygenating and the impacts of this on yeast performance
and repitching and to provide a possible approach to improve
fermentation success.
Neva Parker has been with White Labs, Inc. since 2002. She earned
her B.S. degree in microbiology from Gonzaga University in Spokane,
WA, and first became interested in the brewing industry while
studying abroad in London. Neva currently manages laboratory
operations and has been responsible for the development of new
products and services, as well as researching the effects of various
brewing aspects on yeast performance, using lab-scale fermentation
trials. She has presented at several workshops and conferences and
published articles in brewing magazines. She has been a member of
the ASBC since 2003.
P-135
Can -omics help high gravity brewing?
MAYA PIDDOCKE (1), Stefan Kreisz (2), Hans Heldt-Hansen (1),
Lisbeth Olsson (1)
(1) Center For Microbial Biotechnology, DTU, Denmark; (2)
Novozymes A/S, Bagsvaerd, Denmark
When process optimization and economic savings are the keys
to a brewery’s financial success, high gravity fermentation is an
attractive approach. The challenges of high gravity fermentation
are associated with a number of stressful conditions for yeast such
as high osmotic pressure, less available free amino nitrogen, high
ethanol levels at the end of the fermentations and, as result of
glucose repression, risk of incomplete fermentation. Knowing the
complexity of the problem, modern system biology tools can offer
insight into the physiological state of brewer’s yeast in high gravity
fermentations. However, while trancriptome and metabolome
analyses are routinely used in systems biology to study baker’s yeast,
they are still less popular for studying the brewer’s yeast genome
and its metabolism. Considering the polyploid nature of lager
yeast and the complexity of beer fermentation there still remains
some problems when applying the systems biology approach to
brewer’s yeast. A few case studies based on our own research are
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