Open-Source PCR and Agar-Based Methods for Cost-Effective Detection of Diastatic Yeast

MBAA TQ https://doi.org/10.1094/TQ-58-2-0611-01​  | VIEW ARTICLE

Sarah Traynor, Rona Zhou, Nautica Spence, and Richard Preiss. Escarpment Labs, 18-225 Hanlon Creek Blvd., Guelph N1C 0A1, ON, Canada
 
Abstract
 

Diastatic variants of Saccharomyces cerevisiae are useful yet problematic in the brewing industry. A cross-contamination event by a diastatic strain in a beer can cause considerable problems for the brewery, especially if the contamination goes undetected until the final packaged product. Stringent quality control procedures are required to detect the presence of unintentional diastatic yeast in beer but are often still insufficient for rapidly detecting low-level contaminations. This paper discusses two cost-effective approaches breweries can use to screen for diastatic yeasts. First, a method of DNA isolation using a commercially available extraction kit is presented that enables polymerase chain reaction testing directly from a highly contaminated beer sample without enrichment, affording same-day results. The second approach is a selectiv​e medium that yields fewer false positives than existing approaches and was designed by coupling two well-understood features of diastatic yeast: copper resistance and starch consumption. These methods are simple and cost-effective, making the test more accessible to breweries of all sizes. 

Keywords: diastatic, quality control, STA1, yeast, fermentation, PCR ​

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