Putting beer in the hands of CRISPR

Johan Thevelein, an emeritus professor of Molecular Cell Biology at the Katholieke Universiteit in Belgium, and his team are renowned in their field for their work in developing a platform for the genetic analysis of industrially important traits in yeast to improve industrial yeast strains.

By utilising this technology, they were able to identify the gene(s) responsible for flavour in beer by screening large numbers of yeast strains to evaluate which did the best job of preserving flavour under pressure.

Since the brewing industry made the switch from open vats to large, closed vessels in the 1970s, there has been a noted reduction in the quality of beer, largely due to inadequate flavour production. This is believed to be a result of the carbon dioxide produced during fermentation, which pressurises in the closed vessels and spoils the flavour.

To their surprise, a single mutation in the MDS3 gene was identified, encoding a regulator involved in the production of isoamyl acetate that was responsible for most of the pressure tolerance in this specific yeast strain. Isoamyl acetate is believed to be the source of the banana-like flavour in beer and other alcoholic drinks.

“The mutation is the first insight into understanding the mechanism by which high carbon dioxide pressure may compromise beer flavour production,” said Thevelein, who noted that the MDS3 protein is likely a component of an important regulatory pathway that may play a role in carbon dioxide inhibition of banana flavour production, adding, “how it does that is not clear.”

The researchers then employed the gene-editing technology CRISPR/Cas9 to edit this mutation into other brewing strains, leading to similar improvements in carbon dioxide pressure tolerance and therefore flavour. “That demonstrated the scientific relevance of our findings, and their commercial potential,” said Thevelein.

The research appears in the American Society for Microbiology journal Applied and Environmental Microbiology.