For my PhD thesis, I’ve been researching the flavour- and stress-related properties of brewing yeast hybrids. It has been known for some time that lager yeast (Saccharomyces pastorianus) is actually a hybrid species, and that one parent was the well-known ale yeast Saccharomyces cerevisiae. In 2011, the other side of the family, Saccharomyces eubayanus, was discovered. This discovery has allowed for the improved characterization of lager yeasts, and also opened up the possibility to create new tailor-made lager yeast strains. This is possible through mating of selected strains from the two parent species.

This is exactly what I’ve been doing during the past year, and I’m happy to announce that we recently published our first results (New lager yeast strains generated by interspecific hybridization) in the Journal of Industrial Microbiology and Biotechnology. We mated a strongly flocculent production ale strain (from a brewery in the UK) with S. eubayanus, to produce lager yeast hybrids which performed better than the parent strains, and inherited beneficial properties from both. This will open up the possibility to produce a range of new lager yeast strains, with e.g. interesting flavour production and increased stress tolerance. We already have plenty of new interesting hybrid combinations that I’m looking forward to characterizing. I will post more details in a later post, but in the meanwhile feel free to read the publication if you are interested, it is Open Access!

Link to the publication: http://link.springer.com/article/10.1007/s10295-015-1597-6

Abstract:

The interspecific hybrid Saccharomyces pastorianus is the most commonly used yeast in brewery fermentations worldwide. Here, we generated de novo lager yeast hybrids by mating a domesticated and strongly flocculent Saccharomyces cerevisiae ale strain with the Saccharomyces eubayanus type strain. The hybrids were characterized with respect to the parent strains in a wort fermentation performed at temperatures typical for lager brewing (12 °C). The resulting beers were analysed for sugar and aroma compounds, while the yeasts were tested for their flocculation ability and α-glucoside transport capability. These hybrids inherited beneficial properties from both parent strains (cryotolerance, maltotriose utilization and strong flocculation) and showed apparent hybrid vigour, fermenting faster and producing beer with higher alcohol content (5.6 vs 4.5 % ABV) than the parents. Results suggest that interspecific hybridization is suitable for production of novel non-GM lager yeast strains with unique properties and will help in elucidating the evolutionary history of industrial lager yeast.