For many centuries, beer was brewed in open, horizontal vats. However, in the 1970s, the beer industry switched to using large, closed vessels, which are easier to fill, empty, and clean, enabling brewing of larger volumes of beer at reduced costs. Unfortunately, these modern methods produce inferior quality beer, due to insufficient flavor production.
Now, a team of researchers from KU Leuven in Belgium (a country famous for its wide variety of beers) have managed to improve the flavor of contemporary beer by identifying and engineering a gene which is responsible for much of the flavor of beer and other alcoholic drinks.
During fermentation, yeast converts half of the sugar in the mash to ethanol, and the other half to carbon dioxide. The CO2 pressurizes the closed vessels, dampening beer flavor. To fix this problem, the scientists have developed a groundbreaking technology for identifying genes responsible for commercially important traits in yeast, and applied it to find the genes responsible for flavor in beer by screening a wide variety of yeast strains to evaluate which did the best job of preserving flavor under pressure. The analysis revealed a gene for a banana-like flavor – one of the most important flavors present in beer and other alcoholic drinks.
“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,” said study senior author Johan Thevelein, an emeritus professor of Molecular Cell Biology at KU Leuven.
By using a revolutionary gene editing technology called CRISPR/Cas9, the scientists managed to engineer this mutation in other brewing strains, which similarly improved their tolerance of carbon dioxide pressure, enabling full flavor. “That demonstrated the scientific relevance of our findings, and their commercial potential,” Professor Thevelein explained.
“The mutation is the first insight into understanding the mechanism by which high carbon dioxide pressure may compromise beer flavor production,” he added, stressing that the MDS3 protein is most likely a component of a crucial regulatory pathway that may play a role in carbon dioxide inhibition of banana flavor production.
This technology has also been highly successful in identifying genetic elements contributing to rose flavor production by yeast in alcoholic drinks, as well as other commercially important traits, such as glycerol production and thermotolerance.
The study is published in the journal Applied and Environmental Microbiology.
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