Microbiologists improve the taste of beer


Washington, DC – Belgian researchers have improved the flavor of contemporary beer by identifying and engineering a gene responsible for much of the flavor of beer and some other alcoholic beverages. The search appears in Applied and environmental microbiologya journal of the American Society for Microbiology.

For centuries, beer has been brewed in open, horizontal tanks. But in the 1970s, the industry switched to using large, closed vessels, which were much easier to fill, empty and clean, allowing larger volumes to be brewed and lowering costs. However, these modern methods produced lower quality beer, due to insufficient flavor production.

During fermentation, the yeast converts 50% of the sugar in the mash into ethanol and the remaining 50% into carbon dioxide. The problem: Carbon dioxide pressurizes these closed containers, dulling the flavor.

Johan Thevelein, Ph.D., Emeritus Professor of Molecular Cell Biology at Katholieke Universiteit, and his team pioneered the technology to identify genes responsible for commercially important traits in yeast. They applied this technology to identify the gene(s) responsible for the flavor of beer, screening a large number of yeast strains to assess which were most successful in preserving flavor under pressure. They focused on a gene for a banana flavor “because it’s one of the most important flavors found in beer, as well as other alcoholic beverages,” said Thevelein, who is also a founder of NovelYeast, which collaborates with other companies in industrial biotechnology.

“To our surprise, we identified a single mutation in the MDS3 gene, which codes for a regulator apparently involved in the production of isoamyl acetate, the source of the banana flavor that was responsible for most of the pressure tolerance in that specific yeast strain. “, said Thevelein.

Thevelein and his colleagues then used CRISPR/Cas9, a breakthrough gene-editing technology, to engineer this mutation into other brewing strains, which also improved their tolerance to carbon dioxide pressure, enabling flavor complete. “This demonstrated the scientific relevance of our findings and their commercial potential,” Thevelein said.

“The mutation is the first insight into understanding the mechanism by which high carbon dioxide pressure can compromise beer flavor production,” said Thevelein, who noted that the MDS3 protein is likely a component of a important regulatory pathway that may play a role in carbon dioxide. inhibition of banana flavor production, adding, “how that is unclear.”

The technology has also succeeded in identifying genetic elements important for the production of rose flavor by yeast in alcoholic beverages, as well as other commercially important characteristics, such as glycerol production and thermotolerance.

Thanks to new technologies and cheaper sequencing, researchers are now able to dig deep into the microbes that ferment so many wonderful foods and drinks. Revisit our mSystems Conversation Podcast Episode Editors for more.

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