Do microbes evade domestication? - Evaluating potential ferality among diastatic Saccharomyces cerevisiae

Area of Science:

• Microbiology
• Yeast Genetics
• Food Science

Background:

• Certain Saccharomyces cerevisiae strains possess diastatic activity due to the STA1 gene, enabling starch degradation.
• Diastatic yeasts can contaminate beer, leading to spoilage issues like super-attenuation, gushing, and off-flavors.
• Understanding the origin and transmission of these contaminants is crucial for the brewing industry.

Purpose of the Study:

• To investigate the sources and relationships of diastatic yeast contaminants in a Portuguese craft brewery.
• To analyze the genetic relatedness between environmental and production diastatic yeast strains.
• To explore the evolutionary history and domestication patterns of the STA1 gene.

Main Methods:

• Whole genome sequencing of beer contaminants and environmental yeast isolates.
• Phylogenetic analysis of STA1 and its ancestor SGA1 genes.
• Analysis of domestication signatures in diastatic yeast strains.

Main Results:

• Recurrent diastatic yeast contaminations were linked to environmental strains.
• Some beer contaminants showed close genetic ties to environmental strains from Botswana.
• Evidence suggests a single origin for the STA1 gene, dating back to the emergence of diastatic yeasts.
• Widespread domestication signatures were observed in diastatic strains.

Conclusions:

• Environmental diastatic yeasts are a significant source of brewery contamination.
• Diastatic yeasts may be reverting from domesticated settings to natural environments.
• The evolutionary history of STA1 supports a long-standing lineage of diastatic yeasts.