Program Book - Master Brewers Association of the Americas

P-216
Improving beer flavor and fermentative capacity with selected
beer yeast produced on maltose medium
MUSTAPHA NEDJMA (1), Nicolas Declercq (2), Stylios Matamis
(3), Philippe Cario (2)
(1) Pascal Biotech – Spindal, Gretz-Armainvilliers, France; (2) AEB
Group Beverage Division, Brescia, Italy; (3) Spindal Europe Sud,
Thessaloniki, Greece
Maltose, maltotriose and glucose are the most abundant
fermentable sugars in wort; in the case of incomplete fermentation,
maltotriose can cause a range of qualitative problems in beer and
ethanol loss. Furthermore, yeast which comes pre-grown on glucose
biomass cannot fully adapt itself during beer fermentation. The
development and production of selected beer yeast for fast and
complete metabolization of these three main fermentable sugars
in wort has been considered. The performance of fermentation
is followed through the optimization of the culture medium,
reproducing accurately the wort composition by monitoring yeast
growth, ethanol synthesis, original gravity and attenuation, and
sugars consumption during the fermentative process. Beer flavor
was evaluated through the content of higher alcohols, volatile esters
and aroma compounds. This study demonstrates that the selected
beer yeast Fermaltose obtained from maltose biomass confers a
more stable metabolism, a faster fermentation even in the case of
nitrogen, lipids or vitamin deficiency, an improved maltose and
maltotriose conversion, resistance to ethanol and temperature
impact. The equilibrium and reproducibility of the aromatic profiles
have also been analyzed, in comparison with traditional yeasts after
successive inoculation: mutation, membrane permeability, study of
the permease.
Mustapha Nedjma studied chemistry at the University of Reims
(France) and received his Ph.D. degree in 1995 under the supervision
of Jean Pierre Pete and Alain Maujean on thermal, photochemical,
and catalytic degradation of dithiorbamates and other derivatives
and their impact on the generation of sulfur off-flavors in “Eaux-devie”
of cognac and other alcoholic beverages. This study was followed
by the sulfur metabolism of yeast, Saccharomyces cerevisiae. After
one year of post-doctoral work in the field of biotechnology, he was
named R&D director for Pascal Biotech (Biotechnology division
of AEB Group). His research interests concern biotechnology
development: enzyme production using solid-state fermentation
and microorganism selection, yeast extract development, and yeast
selection and breeding and has participated in many publications
and conferences in this field. Since 2003, he has been scientific
director of biotechnology research and development for AEB Group.
P-217
Nitrogen source starvation induces expression of Lg-FLO1 and
flocculation of bottom-fermenting yeast
TOMOO OGATA (1), Hideyo Tadami (2), Miho Shikata (1), Mami
Izumikawa (1), Yasushi Kitagawa (1)
(1) Asahi Breweries, Ltd. Research Laboratory of Brewing
Technology, Moriya, Japan; (2) Asahi Breweries, Ltd. Research
Laboratory of Food Technology, Moriya, Japan
In brewing, bottom-fermenting yeast flocculates after fermentation
finishes. It is advantageous to brewers because sediment yeast is
required for subsequent fermentation. This flocculation property
seems to be inducible. However, it has not been clear what kinds of
factors are involved in induction of flocculation. We investigated
whether bottom-fermenting yeast flocculated under different
starvation conditions. Only in the case of nitrogen source starvation
did bottom-fermenting yeast flocculate. Not only in the case of
nitrogen source starvation, but also in the case of a nonpreferred
nitrogen source such as proline did bottom-fermenting yeast
flocculate. From these results, it was considered that flocculation
of bottom-fermenting yeast was controlled by a mechanism similar
to NCR (nitrogen catabolite repression). The expression of Lg-
FLO1, which caused flocculation of bottom-fermenting yeast,
was controlled similarly. From these results, it was supposed that
nitrogen source starvation and nonpreferred nitrogen source
induced Lg-FLO1 expression and caused the flocculation of bottomfermenting
yeast.
Tomoo Ogata was born in 1961. He received a M.S. degree in
pharmacology science from Chiba University. After graduation
in 1985, he worked on brewing microbiology at the Research
Laboratory of Brewing Technology, Asahi Breweries, Ltd. He
received a Ph.D. degree in microbiology science from Tokyo
University in 1997.
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