Microbiology Session
Nathan T Traw, Mother's Brewing Company, Springfield, MO, USA
ABSTRACT: The food and beverage industries are affected by
the growing population of microbes that are resistant to current
anti-microbial chemicals. Specifically, the brewing industry is seeing
the emergence of new beer spoiling organisms that were previously not a
concern. Bacillus species are used as an organic pesticide in the
United States by hop growers. This experiment seeks to correlate the
spoilage of microbrewery beer by Bacillus species and its use as
an organic pesticide by the hop industry. Spoiled beer from a recently
opened microbrewery was plated on Schwarz differential agar (SDA). Bacillus
was isolated and confirmed by traditional microbiology methods that
included Gram staining, endospore staining, and enzyme tests. The
microbrewery’s hops were then analyzed. Hops were supplied by the
microbrewery and were commercial pelletized hops purchased from a
brewer’s supply store. The hops were in a vacuum sealed bag and
pelletized. The hops used by this particular microbrewery were not
purchased as organic. Hops were aseptically sampled and placed in
sterile nutrient broth. After 24 hr of incubation, 400 µL of the
nutrient broth was plated on SDA. Bacillus was confirmed by traditional microbiology methods as the sole isolate from the hops. The Bacillus
culture isolated from the hop sample was then incubated in microbrewery
beer. After 48 hr of incubation, the beer was observed microscopically
for Bacillus. The presence of live Bacillus cells was confirmed. This confirms that a beer-resistant strain of Bacillus
introduced by commercially prepared hops is capable of spoiling
microbrewery beer by unknown mechanisms. Future studies on this topic
include beer stability, dissolved oxygen concentrations, and genetic
sequencing.
Nathan Traw received his B.S. degree in
biology-microbiology and biotechnology from Missouri State University in
May 2011. During his time at MSU, Nathan spent nearly two years as a
student researcher studying the transcription of genes in macrophages in
response to bacterial stimuli. Nathan is now the quality assurance and
control lead for Mother’s Brewing Company in Springfield, MO. He is
currently preparing for the 2012 IBD Diploma in Brewing examinations.
