Evaluation of NBB-PCR: A Reliable, Fast and Universal Enrichment Broth for the PCR Detection of Beer Spoiling Microorganisms

Introduction: The detection of microorganisms using rapid methods, like PCR or real-time PCR, have gained importance in a brewery’s quality control. Although these methods permit fast and reliable detection of beer spoilers, the cultural enrichment of these samples is still a crucial step - especially for slow growing microorganisms. A suitable enrichment medium should induce fast microbial growth. We demonstrate a new culture medium, NBB-PCR Broth, with an optimized nutrient composition for enrichment of beer spoiling microorganisms (within 48 h), allowing an optimal detection with PCR or real-time PCR.

Purpose: The aim was to develop a fast, universal enrichment medium for all relevant beer spoilers that is compatible with all common PCR detection methods and sample types arising in a brewery, to ensure reliable results.

Methods: The new broth was tested with the strains Lactobacillus brevis, Lactobacillus lindneri, Pediococcus damnosus and Pectinatus frisingensis (100 cells/ml, n=3). Samples of filterable beer, cloudy beer, pitching yeast and cropped yeast (n=3 each) were spiked with 100 cells/sample of the respective microorganism. After incubation at 28°C, samples were analyzed with four real-time PCR systems, as well as a novel PCR based lateral flow detection system.

Results: The developed enrichment medium was compatible with all tested PCR or real-time PCR systems, with no false positive results or inhibition of PCR observed. After 48 h of enrichment, all tested microorganisms reached reliable detection levels or showed significant reduction in Ct-values. L. brevis and even slow growing L. lindneri were already detectable after 24 h (by one of the tested PCR systems).

Significance: NBB-PCR Broth is a reliable, ready-to-use enrichment medium that allows PCR or real-time PCR detection of beer spoilers (in 48 h), as demonstrated with four differing test strains. Its compatibility with all market-relevant PCR systems enables a dramatic decrease of the detection time and enables faster product release in the breweries.