Isolation of novel beer-spoilage bacteria from the brewery environment

Two strains of beer-spoilage bacteria, BS-1 and EM-63, were isolated from the environment (from drainage) in our breweries. Strain BS-I belonged to a home-fermentative species of the genus Lactobacillus. The partial sequence of 16S rDNA indicated that strain BS-I was related to Lactobacillus coryniformis. However, the fermentation pattern of the sugars was different from that of L. coryniformis and other species of Lactobacillus, because of the narrow fermentation spectrum, glucose, mannose, and fructose. Strain EM-63 was a Gram-negative, strictly anaerobic rod-shaped bacterium with no flagella. The GC content of DNA was 41%, and the cell wall peptidoglycan was directly cross-linked meso-diaminopimelic acid. The major fermentation acids were succinic acid and D-lactic acid in the culture media, while propionic acid was neither produced in culture media nor in beer. These characteristics indicated that strain EM-63 did not belong to the genus Pectinatus, known as Gram-negative, rod-shaped, beer-spoilage bacteria, or the genus Zymophilus or Selenornonas, known as Gram-negative, rod-shaped, pitching yeast contaminants. On the basis of the physiological characteristics and genetic analysis, we conclude that these strains are novel beer-spoilage bacteria.