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Beer is a fermented beverage in which microbial activity is central to its production, defining the characteristics of the final product. The diversity of microorganisms present in this process is, however, relatively limited, mainly owing to its restrictive environment, such as the iso-α-acids from hops and ethanol, which have antimicrobial activity. Despite these unfavorable conditions for bacterial growth, some beer spoilers are able to grow in beer. Lactic acid bacteria (LAB) are reported to be responsible for approximately 70% of all beer-spoilage incidents. These beer spoilers have the common characteristic of resistance to iso-α-acids found in hops given by genetic elements such as ORF5 and the multidrug transporter horA. However, the tolerance to hop compounds could be a multifactorial trait that includes the bacterial species and the hop-resistance genes. So it is important to track the bacterial beer-spoiler species and hop-resistance genes in a brewery environment. In this work we isolated 10 beer-spoiling LAB strains and one Bacillus sp. from a commercial brewery environment, and we found hop-resistance genes in nine out of the 10 LAB strains and also in the non–beer spoiler Bacillus. The isolated LAB strains were identified by rRNA 16S gene sequence and digestion with the restriction enzyme BfaI, resulting in four species, Lactobacillus rossiae, Pediococcus damnosus, Lactobacillus brevis, and Lactobacillus casei. Most of the strains and hop-resistance genes were found in the environment of the fermentation stage. Keywords: Pediococcus, Lactobacillus, Beer-spoiler, horA, ORF5
