The secret of classic Belgian beers? Medieval super-yeasts

An international team of scientists led by Prof. Kevin Verstrepen (VIB-KU-Leuven) and Prof. Steven Maere (VIB-UGent) has discovered that some of the most renowned classic Belgian beers, including Gueuze and Trappist ales, are fermented with a rare and unusual form of hybrid yeasts.

These yeasts combine DNA of the traditional ale yeast, Saccharomyces cerevisiae, with that of more stress-resistant feral yeasts such as Saccharomyces kudriavzevii.

"These yeasts are hybrids between two completely different species" says Dr. Jan Steensels (VIB – KU Leuven Center for Microbiology), who coordinated the lab work of this study. "Think of lions and tigers making a super-baby."

Such interspecific hybridizations are rare and seem to be favored by the domestication process. In this case, the new hybrid yeasts combined important characteristics of both parental species, with the fermentation capacity of normal beer yeasts and the stress tolerance and capacity to form special aromas of more feral ancient yeasts like S. kudriavzevii that haphazardly made their way into the brewery.

The team, from the VIB-KU Leuven Center for Microbiology and the University of Munich, supported by industrial partners, has spent five years characterizing the different yeasts used in today's production of beer, wine, bread and biofuels. The genetic analysis of these yeasts was quite a piece of work, because none of the existing pipelines for DNA sequencing can deal with such mixed origins.