Matthew Bochman (1),
Adam Covey (2), Cody Rogers (1), Caleb Staton (2), Devon Veatch (3)
; (1) Indiana University, Bloomington, IN, U.S.A.; (2) Upland Brewing
Company, Bloomington, IN, U.S.A.; (3) Ivy Tech Community College of
Indiana, Bloomington, IN, U.S.A.
Technical Session 8: Yeast Stress & Performance
Monday, August 15 • 8:15–9:30 a.m.
Tower Building, Majestic Level, Majestic Ballroom
During beer fermentation, the brewer’s yeast Saccharomyces cerevisiae
experiences a variety of shifting growth conditions, culminating in a
low-oxygen, low-nutrient, high-ethanol, acidic environment. In beers
that are bottle conditioned (i.e., carbonated in the bottle by supplying
yeast with a small amount of sugar to metabolize into CO2), the S. cerevisiae
cells must overcome these stressors to perform the ultimate act in beer
production. However, medium shock caused by any of these variables can
slow, stall, or even kill the yeast, resulting in production delays and
economic losses. Here, we describe a medium shock caused by high lactic
acid levels in an American sour beer, which we refer to as “terminal
acidic shock.” Yeast exposed to this shock failed to bottle condition
the beer, though they remained viable. The effects of
low-pH/high-[lactic acid] conditions on the growth of six different
brewing strains of S. cerevisiae were characterized, and we
developed a method to adapt the yeast to growth in acidic beer, enabling
proper bottle conditioning. Our findings will aid in the production of
sour-style beers, a trending category in the American craft beer scene.
Matt Bochman received his B.S. degree in molecular biology from
Juniata College in Huntingdon, PA, in 2003 and his Ph.D. degree in
molecular, cellular, and developmental biology from the University of
Pittsburgh in 2008 and was an American Cancer Society postdoctoral
research fellow at Princeton University. Since 2013, he has been an
assistant professor in the Molecular & Cellular Biochemistry
Department at Indiana University in Bloomington, IN. During his 15 years
in research labs, he has used various yeasts as model organisms to
answer scientific questions, as well as to brew beer and hard cider.
Recently, he has put his yeast skills to good use as a craft brewery and
distillery consultant and co-founded Wild Pitch Yeast, LLC to supply
yeast-related services to these industries in the American Midwest.