Detection of spoilage bacteria in beer by polymerase chain reaction

Cultivation methods for the detection of bacteria in beer, although simple and sensitive, are time-consuming and lack specificity. In this study, the sensitivity of a polymerase chain reaction (PCR) assay consisting of an eas y sample treatment and specific primers for Lactobacillus lindneri, L. brev is, Megasphaera cerevisiae, and Pectinatus spp, was improved by pre-enrichm ent. A pre-enrichment broth supporting the growth of lactobacilli and anaer obic beer spoilers better than currently used media was formulated. For det ermination of the pre-enrichment times needed for PCR detection of these co ntaminants, artificially contaminated beer samples were mixed with the pre- enrichment broth and incubated anaerobically at 30 degrees C. Low levels of lactobacilli (less than or equal to 10 CFU/100 ml) were detected after 1-3 days, Pectinatus spp, after 2-4 days, and M. cerevisiae after 2-3 days of pre-enrichment, depending on the strain and the alcohol content of the beer . After the pre-enrichment, the PCR analysis took <8 hr. The time saving co mpared to corresponding conventional methods requiring up to several weeks is marked, especially for L. lindneri, M. cerevisiae, and Pectinatus spp. M oreover, the assay described allows species- or genus-level detection of th e most harmful beer spoilage bacteria in finished beer and is sensitive and simple enough for routine work.