Last week Finnish researchers reported they had developed a better way to develop yeast that would give us more diverse tastes, save money and time. From their 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.
The new yeast development process is below, in detail:
The team decided to focus on the two species, S. cerevisiae and S. eubayanus. Instead of using complex molecular biological techniques, they chose instead to do things the old fashioned way by forcing the two to interact. The process takes advantage of auxotrophy, in which an organism cannot produce a molecule necessary for survival. Without external addition of the nutrient, the cell dies. In this case, the team used a strain of S. eubayanus unable to make the amino acid lysine and a strain of S. cerevisiae unable to produce a component of RNA, uracil.
When it was time to make the hybrids, the group simply took both strains and put them into a basic medium without supplementation of either lysine or uracil. Then, they waited for 3 to 7 days. Sure enough, colonies began to appear, meaning they had hybrids capable of making both molecules. Using a combination of genetic identification techniques, the establishment of these new strains containing pieces of both parental yeasts was confirmed.
Popular Science expanded on the research and gives us insight into how the Finnish research could lead to “better taste and aroma” – something we can all get behind! The new process produced more hearty strains of yeast that could withstand environments that previous strains could not. Further, and just as useful to brewery economics, they produced a higher concentration of alcohol. More hearty, diverse and more efficient. All through natural processes.
Using a combination of genetic identification techniques, the establishment of these new strains containing pieces of both parental yeasts was confirmed.
Once the hybrids were developed, the real fun could begin. Using traditional brewing methods, the new strains were given the opportunity to prove themselves in the wort. The results were fascinating. First, the hybrids were stable at both warm and cool temperatures such that they could survive in environments the parents could not stand. They also reduced the time for fermentation not by hours but days. Finally, and perhaps more interestingly, they produced more alcohol than their parents. By the end of the fermentation process, the concentration was between one and two percent higher.
But the real test was could the new process they had developed produce better tasting beer?
The levels of fruitiness were as high if not higher than the parents while the levels of the methyl alcohols were lower. The beers were not only better in chemistry but would also make for excellent quaffs.
There was one more benefit to these yeasts although this had less to do with the chemistry and more to do with public perception. Because the formation of these new strains was done through an entirely natural process, it would be considered non-genetically-modified. This meant these strains could be used in regular manufacture without any concern from regulatory or other oversight.
It looks like science is taking an interest in craft beer, just like the rest of the world!