PCR-fingerprinting of culturable yeasts from commercially obtained beers: a simple and engaging applied microbiological laboratory exercise.

Yeast and fermented products present an opportunity to introduce students to applied microbiology. We designed and implemented a project-oriented laboratory class where yeasts from bottled beverages were isolated and compared using DNA fingerprinting and Sanger-sequencing. We recovered 17 Saccharomyces isolates, and two non- Saccharomyces yeasts. Fingerprinting identified two groups of closely related Saccharomyces isolates in unrelated beer styles, later identified as diastatic and wine yeasts using phylogenomics. Isolates from traditional products thus may not represent the original fermentation. We believe that the interlinked nature of topics and the simple basis can elevate engagement and performance of students during such a class.