Moderate expression and activity of flocculins underlie the characteristic flocculation phenotype of Saccharomyces pastorianus.

Moderate expression of multiple FLO genes underpins the flocculation phenotype of Saccharomyces pastorianus, with deletion of key genes only delaying sedimentation in brewing.

• Why it matters: Understanding the genetic basis of flocculation in lager yeast is crucial for optimizing brewing performance, yeast recovery, and beer quality, especially given the complex hybrid genomes involved.
• What they did: Thirteen FLO genes, including novel variants like Flo12, were identified and functionally characterized in CBS 1483 using re-annotation, structural modeling, and optogenetic expression; gene deletions revealed redundancy and compensatory mechanisms.
• The result: Flocculation arises from the combined action of several moderately active adhesion proteins, and deleting the strongest genes only delays sedimentation, indicating a robust network that maintains brewing efficiency.