De Novo Hybridization Approach Expands Diversity of Industrially Applicable Lager Yeast Strains with Unique Genome Composition

ABSTRACT | Lager beer is produced by Saccharomyces pastorianus, which is a natural allopolyploid hybrid between S. cerevisiae and S. eubayanus. Lager strains are classified into two major groups based largely on genomic composition: group I and group II. Group I strains are allotri-ploid, whereas group II are allotetraploid. A lack of phenotypic diver-sity in commercial lager strains has led to substantial interest in the reconstitution of de novo allotetraploid lager strains by hybridization of S. cerevisiae and S. eubayanus strains. Such strategies rely on the hy-bridization of wild S. eubayanus isolates, which carry unacceptable traits for commercial lager beer such as phenolic off-flavors and incom-plete utilization of carbohydrates. Using an alternative breeding strat-egy, we have created de novo lager hybrids containing the domesticated S. eubayanus subgenome from an industrial S. pastorianus strain by hybridizing this strain to a variety of S. cerevisiae ale strains. Five de novo hybrids were isolated that had fermentation characteristics similar to those of prototypical commercial lager strains but with unique phe-notypic variation due to the contributions of the S. cerevisiae parents. Genomic analysis of these de novo lager hybrids identified novel al-lotetraploid genomes carrying three copies of the S. cerevisiae genome and one copy of the S. eubayanus genome. Most importantly, these hy-brids do not possess the negative traits that result from breeding wild S. eubayanus. The de novo lager strains produced using industrial S. pas-torianus in this study are immediately suitable for industrial lager beer production. 

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Publication: MASTER BREWERS ASSOCIATION OF THE AMERICAS | TECHNICAL QUARTERLY | vol. 58, no. 2, pp. 106-116, Nov 2, 2021

Authors: Zachari Turgeon, Ryan C. Jurgens, Thomas Sierocinski, Cedric A. Brimacombe, Yiqiong Jin, Jessica M. Swanson, and John I. Husnik, Renaissance BioScience Corp., Vancouver, Canada