Today’s tall cylindrical fermentation tanks that have replaced the shorter vats of breweries in the past have tended to negatively impact the taste of the resulting beer – but now scientists have stepped in to improve the taste of our booze.
These tall tanks can produce more beer for less money – they’re easier to fill, empty and clean – but their widespread adoption also means excess pressure from the carbon dioxide produced during fermentation, and that affects flavor.
The researchers began by identifying strains of the Saccharomyces cerevisiae yeast that were particularly CO2-resistant, focusing on the production of isoamyl acetate that gives beer its fruity, banana-like flavor.
After finding a particularly robust strain, the team then used a whole-genome sequence analysis to figure out what made it so adept at being able to keep its fruity flavor even under the pressure of modern fermentation tanks.
“To our surprise, we identified a single mutation in the MDS3 gene, which codes for a regulator apparently involved in production of isoamyl acetate, the source of the banana-like flavor that was responsible for most of the pressure tolerance in this specific yeast strain,” says molecular biologist Johan Thevelein, from Katholieke Universiteit Leuven in Belgium.
With this discovery, the researchers were then able to use the CRISPR/Cas9 gene editing technique to engineer the same mutation in other yeast strains. After editing, these strains could better withstand CO2 pressure and better retain their flavor.
Further down the line, many yeast strains could be modified in the same way, leading to beers with a fuller flavor when they’re poured.
So far, it doesn’t appear that other traits of the yeast strain are affected by the genetic edits.
“The mutation is the first insight into understanding the mechanism by which high carbon dioxide pressure may compromise beer flavor production,” says Thevelein.
Before now, it hasn’t been clear exactly how high CO2 pressure has been having an impact on beer flavor at the molecular level, even though the end results in terms of the drop in fruitiness have been easy to taste.
In the future, the researchers want to run experiments with even higher CO2 pressures to see if different genes are identified. A number of other genes showed promise in this study too, though MDS3 was the dominant one.
The same gene identification technology has also previously been used to highlight other important traits in yeast, including the production of glycerol (a sugary alcohol that adds to the taste), and tolerance towards increased temperatures.
The authors are up front about the fact the work was supported by a brewing company, which hopes to make use of the technology in a patent.
While other brands of brew might miss out on the technology, the study does demonstrate the potential benefits in applying CRISPR to tweaking yeast’s talents for making an exceptional drop.
“This work shows the strong potential of polygenic analysis and targeted genetic modification for creation of cisgenic industrial brewer’s yeast strains with specifically improved traits,” write the researchers in their published paper.
The research has been published in Applied and Environmental Microbiology.