Yuki Asakawa (1), Masayuki Aizawa (1), Kazumaru Iijima (1), Yasuo Motoyama (1), Satoshi Shimotsu (1), Koji Suzuki (1); (1) Asahi Breweries, Ltd., Moriya-Shi, Japan

Yeast, Fermentation, and Microbiology

Only a few microbial species can spoil beer because the growth of microorganisms is inhibited by several factors in beer. The genus Lactobacillus is known as a predominant beer spoiler. In this study, Lactobacillus sp. ABBC641, isolated from beer and originally deposited to VTT culture collection, exhibited beer-spoilage ability by spoiling several pilsner-type beers within the range of pH 4.1-4.6 and 10-20 bitterness units. A PCR study also showed that the strain carries hop resistance genes, horA and horC. Since these data indicate that ABBC641 is a potential beer spoiler, further identification and taxonomic studies were conducted. The complete 16S rRNA gene sequence analysis showed that ABBC641 is closely related to Lactobacillus rossiae and Lactobacillus siliginis with 97% similarity to each type strain, while it is generally considered that over 98.7% similarity to the type strain is necessary to be identified as the same species. In addition, the DNA–DNA hybridization result indicated that the type strains of L. rossiae and L. siliginis exhibited 4% and 12% relatedness to ABBC641, respectively, suggesting that ABBC641 belongs to neither L. rossiae nor L. siliginis. Furthermore the carbohydrate fermentation profile of ABBC641 was slightly different from those of L. rossiae and L. siliginis. Taken collectively, these results revealed that ABBC641 belongs to a novel Lactobacillus species.

Yuki Asakawa received a master’s degree in engineering from the Tokyo Institute of Technology, Japan, in March 2013 and joined Asahi Breweries Ltd. She has been working on microbiological quality assurance of alcohol beverages and developing microbiological quality control test method for breweries in the Department of Fermentation and Microbiology Technology of Research Laboratories for Alcoholic Beverages.