Flocculation gene variability in industrial brewer's yeast strains.
The brewer's yeast genome encodes a 'Flo' flocculin family responsible for flocculation. Controlled floc formation or flocculation at the end of fermentation is of great importance in the brewing industry since it is a cost-effective and environmental-friendly technique to separate yeast cells from the final beer. FLO genes have the notable capacity to evolve and diverge many times faster than other genes. In actual practice, this genetic variability may directly alter the flocculin structure, which in turn may affect the flocculation onset and/or strength in an uncontrolled manner. Here, 16 ale and lager yeast strains from different breweries, one laboratory Saccharomyces cerevisiae and one reference Saccharomyces pastorianus strain, with divergent flocculation strengths, were selected and screened for characteristic FLO gene sequences. Most of the strains could be distinguished by a typical pattern of these FLO gene markers. The FLO1 and FLO10 markers were only present in five out of the 18 yeast strains, while the FLO9 marker was ubiquitous in all the tested strains. Surprisingly, three strongly flocculating ale yeast strains in this screening also share a typical 'lager' yeast FLO gene marker. Further analysis revealed that a complete Lg-FLO1 allele was present in these ale yeasts. Taken together, this explicit genetic variation between flocculation genes hampers attempts to understand and control the flocculation behavior in industrial brewer's yeasts.
Van Mulders
Sebastiaan E
SE
Centre for Malting and Brewing Science, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, 3001 Leuven, Heverlee, Belgium. Sebastiaan.vanmulders@biw.kuleuven.be
Ghequire
Maarten
M
Daenen
Luk
L
Verbelen
Pieter J
PJ
Verstrepen
Kevin J
KJ
Delvaux
Freddy R
FR
D002448:Cell Adhesion; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005800:Genes, Fungal; D014644:Genetic Variation; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D017422:Sequence Analysis, DNA
D004271:DNA, Fungal