Effect of autolytic by-products on PCR-detection of beer spoilers in yeast slurry

Abstract

The detection of wild yeasts and bacteria within stores of brewing yeast is a standard activity executed at most commercial breweries, however due to the complexity of the sample matrix often contaminants remain undetected. Wild Saccharomyces spp., particularly the dextrin hydrolyzing variant S. cerevisiae var. diastaticus, can pose a unique problem for commercial brewers as these organisms are morphologically similar to brewer's yeast and may lead to the undesired recall of affected batches. It is for this reason that a reliable method has to be developed to detect low concentrations as quickly as possible. Here we propose a new DNA extraction procedure and real-time PCR assay that reliably detects S. cerevisiae var. diastaticus without the timely preenrichments. Furthermore the method removes the inhibitory effects traditionally caused by high concentrations of brewing yeast and autolytic degradation products.