M. A. VINJE (1), C. A. Henson (1), S. H. Duke (2); (1) USDA-ARS
Cereal Crops Research Unit, Madison, WI, U.S.A.; (2) University of
Wisconsin-Madison, Department of Agronomy, Madison, WI, U.S.A.
Poster
Grains of the malting barley cultivar Legacy were micromalted (MM) in a
Joe White micromalting system by the USDA-ARS Cereal Crops Research Unit
or laboratory germinated (LG) on germination paper in petri dishes. MM
grains were sampled daily from 0 to 5 days after imbibition/steeping
(DAI). LG grains were sampled one additional day (6 DAI). Additionally, a
final malt sample was obtained by kilning grain from the 5 DAI MM
sample. The accumulation of sugars (glucose, sucrose, fructose, maltose,
maltotriose, maltotetraose, maltopentaose, maltohexaose, and
maltoheptaose) was monitored at all DAI in both MM and LG grains.
Similar patterns (0–5 DAI) were observed between MM and LG grains for
most sugars. Glucose accumulation in MM grains matched the pattern of LG
grains between 0 and 4 DAI, but MM grains continued to increase after 4
DAI, whereas the glucose levels in LG grains were stable between 4 and 6
DAI. However, accumulation of sucrose, maltose, maltotriose,
maltotetraose, maltopentaose, and maltohexaose occurred slightly earlier
in MM grains than LG grains. Fructose and maltoheptaose accumulation
followed a very similar pattern in both MM and LG grains. The osmolyte
concentration (OC) increased in a pattern similar to that of sucrose,
maltose, maltotriose, maltotetraose, maltopentaose, and maltohexaose. MM
grains rapidly increased in OC between 0 and 1 DAI, whereas LG grains
had the biggest increase in OC from 1 to 2 DAI. Starch levels were also
monitored throughout MM and LG. The starting starch content in the MM
grains was higher than the LG grains, but both MM and LG grains followed
a similar pattern of percent starch degraded from 0 to 5 DAI.
Alpha-amylase activity in MM grains was first observed at an earlier DAI
and had a steeper increase in activity than alpha-amylase activity in
LG grains. MM grains also had significantly higher alpha-amylase
activity than LG grains at 1–5 DAI. Beta-amylase activity in both MM and
LG grains followed essentially the same pattern, with activity
increasing slightly from 0 to 2 DAI and remaining the same from 2 to 5
DAI. The accumulation of the beta-amylase protein was monitored in both
germination treatments. Interestingly, beta-amylase degradation was
observed at 2 DAI, with additional degradation observed between 3 and 5
DAI. In LG grains, beta-amylase degradation occurred at the same time as
MM grains (2 DAI) but with more significant degradation. Beta-amylase
in LG grains was significantly degraded at 4 DAI and not observable at 5
DAI using our Bmy1 specific antibody (epitope located in the C
terminus). These data indicate that beta-amylase undergoes C-terminal
processing during germination (both MM and LG treatments) without
affecting activity.
Marcus A. Vinje received his B.S. degree in 2004, with a major in
genetics, and his Ph.D. degree in 2009, with a major in agronomy, both
from the University of Wisconsin-Madison. He was awarded the Sierra
Nevada Brewing Company Scholarship in 2008 from the American Society of
Brewing Chemists. After graduation in 2009, he was a post-doctoral
research associate at the USDA-ARS Cereal Crops Research Unit until he
joined the department permanently as a research geneticist in 2012.
Marcus has extensively researched both barley beta-amylase genes (Bmy1 and Bmy2),
and his current research is focused on understanding the regulation of
malting quality genes in developing and germinating barley grains.
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