Microbiology Session
Anneleen Wieme, University College Ghent, Faculty Applied Bioscience Engineering, Laboratory of Brewing and Biochemistry, Ghent, Belgium
Co-author(s): Anita Van Landschoot, University College Ghent, Faculty
of Applied Bioscience Engineering, Laboratory of Brewing and
Biochemistry, Ghent, Belgium; Peter Vandamme, Ghent University, Faculty
of Science, Laboratory of Microbiology, Ghent, Belgi
ABSTRACT: Beer is a beverage with good microbiological
stability because it contains almost no oxygen and nutrients for
bacterial growth. In addition, low pH, high CO2 content, and
the presence of ethanol and antibacterial hop compounds ensure microbial
stability. Nevertheless, beer spoilage induced by bacteria is a common
problem in the brewing industry and these spoilage bacteria typically
cause visible turbidity, acidity, and off-flavors. Currently, these
bacteria are detected with culture-dependent methods using selective
media or with faster identification methods such as DNA typing,
ribotyping, and other PCR-based techniques. These approaches are
notoriously laborious, expensive, time-consuming, and, moreover, lack
specificity and sensitivity. The present study aims to develop a quick,
specific, and inexpensive method to detect and identify beer spoilage
bacteria in the brewing industry. To achieve this, an extensive database
comprising MALDI-TOF MS profiles of more than 260 established and
accurately identified contaminants and beer spoilage strains was built.
In addition to these strains, strains of the same species originating
from other niches, besides spoiled beer, were also included in order to
encompass the phenotypic diversity of the spoilage species. Among
others, strains of Lactobacillus brevis (29), L. lindneri (3), “L. brevisimilis” (1), L. buchneri (5), L. coryniformis (1), L. plantarum (8), L. parabuchneri (15), L. paracollinoides (2), L. perolens (10), Pediococcus damnosus (9), Pediococcus inopinatus (10), Pectinatus cerevisiiphilus (1), Pectinatus frisingensis (2), Selenomonas lacticifex (1), Megasphaera cerevisiae (2), and Zymophilus raffinosivorans
(2) were included in the database. The resulting set of profiles
(±6,500 good quality profiles) allowed the assignment of reproducible
species-specific biomarker peaks for all spoilage species. All strains
were not only cultured under species-specific conditions (type medium,
growth temperature, oxygen requirements, growth time), but also on
selective and non-selective media. Different media were used to enable
the exclusion of medium-associated peaks from species-specific biomarker
peaks. Consequently, identification of novel beer spoilage isolates can
be easily and rapidly performed. Nevertheless, the final aim of this
research was to detect and identify these bacteria in a spoiled sample
with minimal, time-consuming culture steps. Financial support was
provided by the Research Fund of the University College Ghent.
Anneleen
Wieme graduated in 2009 as a master in industrial sciences biochemistry
at the University College Ghent. Currently, she is working at the
University College Ghent, and in association with Ghent University she
is performing her Ph.D. studies at the Laboratory of Microbiology at the
Faculty of Sciences. In the future the results of her Ph.D. thesis,
“Exploration of MALDI-TOF MS as a Fast Identification Tool for Beer
Spoilage Bacteria,” will help the brewing industry in quickly
identifying and controlling bacterial beer spoilage.
VIEW PRESENTATION 168
