Pediococcus damnosusstrains isolated from a brewery environment carry thehorAgene

Abstract

Beer is recognized as a safe beverage, owing to its excellent microbiological stability provided by its components, especially iso-α-acids from hop and ethanol which have antimicrobial activity. Despite these unfavourable conditions for bacteria, some lactic acid bacteria (LAB) can cause beer spoilage. Resistance to hop compounds is caused, in part, by the product of genes like horA. Understanding how LAB adapts to hop compounds as well as quick detection of these microorganisms is necessary to ensure high-quality beverages produced by the brewing industry. In this work, we searched for the presence of two main hop-resistance genes, horA and ORF5, and determined the capacity of four strains of Pediococcus damnosus isolated from a brewery environment to grow in the presence of increasing concentrations of iso-α-acids. All strains were able to grow in increasing concentrations of iso-α-acids up to 150 μg mL À1 . This amount is 10 times greater than the concentration in average beer. Genetic amplification of genes associated with hop-resistance, demonstrated the presence of horA, but not ORF5 in all tested strains. This communication represents the first report of the presence of horA gene in bacteria isolated from breweries in our country.

Inhibitory Effects of Iso-α and β Hop Acids Against Pediococcus pentosaceus

“…After 24 h incubation, under iso-α acid stress, the bacteria developed a resistance, thus reducing their sensitivity and consequently the kinetics of their destruction, while under β acids stress they were tolerant. Similarly, a study released by Garcia et al (2016), showed that the Pediococcus bacteria were able to grow and adapt to increasing concentrations of hop compounds in culture media and beer, which shows that it could be considered a potential beer spoiler.…”

Mixed-Culture Metagenomics of the Microbes Making Sour Beer

“…Similar to Lactobacilllus spp., Pediococcus spp. are commonly considered as beer and manufacturing environmental contaminants, a characteristic that encourages research into the identification of resistance factors mainly acquired through specific plasmids and genes [17,22]. In Lambic-style beers (produced by spontaneous fermentation), P. damnosus is one of the main isolated species and can be easily identified as part of the microbiome of the interior surface of wooden barrels [1], in the air, and on other brewery equipment surfaces [23] mainly due to its high oxidative stress resistance and hop tolerance [4].…”