Identification of Microflora in a Biological Brewer’s Wort Acidification Process Run Continuously for 20 Years

Biological acidification is a common and beneficial way for breweries to adjust the pH value of their mash or wort to improve enzymatic activity during mashing, raise yeast activity during fermentation, and increase the flavor stability of the finished beer. The reactors are mostly run for many years without re-inoculating a fresh culture, creating the possibility of changes in the culture, genetic drifts, or the survival of different strains. In this study, a biological acidification culture that had been continuously run for 20 years was analyzed by GTG5 PCR and IGS2-314 rDNA PCR fingerprinting, as well as 16S and 26S rDNA sequencing, and real-time PCR was applied to differentiate the bacterial and yeast strains and species. The applied real-time PCR primers for Lactobacillus amylolyticus and Lactobacillus amylovorus have not been published yet. It was shown that only strains of the species L. amylolyticus were present, with low contamination of yeast strains from the species Saccharomyces cerevisiae. As the original starter culture was Lactobacillus amylolyticus, the acidification plant ran for 20 years, and no Lactobacillus sp. cross-contamination could be analyzed using culture-dependent methods after 20 years. The microflora composition is a decisive factor for the final beer flavor.