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32. Isolation and identification of antibacterial compounds against Gram-negative anaerobic bacteria from beer

Hajime Nakata (1), Hajime Kanda (1), Takeshi Kaneko (1), Yasukazu Nakakita (1), Takeshi Nakamura (1), Koji Takazumi (1); (1) Sapporo Breweries Ltd., Frontier Laboratories of Value Creation, Yaizu, Japan

Technical Session 9: Brewing Microbiology
Monday, August 15  •  9:45–11:30 a.m.
Plaza Building, Concourse Level, Governor’s Square 14

Beer is a microbiologically stable beverage since it contains ethanol and hop bitter compounds. In addition to the presence of such antimicrobial substances, the pH of beer is relatively low, and it contains limited nutrients and oxygen. In spite of such a severe environment, a few kinds of bacteria can grow in beer. As for beer spoilage bacteria, four genera, Lactobacillus, Pediococcus, Pectinatus, and Megasphaera, can cause quality issues with beer production in the brewery, so it is important to discriminate beer spoilage bacteria from others to minimize the risk of spoilage incidents. In gram-positive bacteria such as Lactobacillus and Pediococcus, hop resistance genes, horA and horC, are reported to be responsible for beer spoilage ability. Additionally, a detection method based on these genes has already been developed. On the other hand, in gram-negative bacteria such as Pectinatus and Megasphaera the growth mechanism in beer has not been revealed. Therefore, a species-specific identification method, based on 16S rRNA gene analysis, is used to determine their beer spoilage ability. However, with this method, there is a possibility of missing novel gram-negative beer spoilage bacteria. The objective of this study is to test the hypothesis that beer contains unknown antibacterial compounds against gram-negative bacteria. In order to prove this hypothesis, we tried to isolate and identify antibacterial compounds against gram-negative bacteria from beer. XAD gels and a C18 ODS column were used to isolate the antibacterial compound from beer, and LC/MS analysis revealed that the active fraction contains compound A. Compound A exhibited antibacterial ability against Bacteroides, Prevotella, and Fusobacterium spp. but not against Veillonella or Enterobacter spp. Especially in obligate anaerobic bacteria, there are two types of bacteria: those that have compound A tolerance and those that do not. Our study suggests the possibility that compound A regulates the growth of gram-negative anaerobic bacteria in beer.

Hajime Nakata received a master’s degree from the Graduate School of Life Sciences, University of Tohoku, Japan. He began his career as a microbiologist in April 2012 at the Frontier Laboratories of Value Creation, Sapporo Breweries Ltd. He mainly studies the beer spoilage ability of bacteria.