Genetic pre-adaptations in Saccharomyces cerevisiae Andean chicha isolates facilitate industrial brewery application.

Strains of Saccharomyces cerevisiae were isolated from a traditionally produced Andean maize-based chicha from Ecuador and characterised with respect to their potential use in industrial beer brewing. Whole-genome sequencing revealed that the strains were related to the 'French Guiana' and 'Mexican Agave' S. cerevisiae clades, though the available evidence indicates that they belong to a previously undescribed population, and are thus unrelated to traditional European brewing strains. Small-scale screening for wort fermentation revealed two strains with brewing potential. These outperformed commercial reference brewing strains and had fermentation profiles and alcohol yields similar to those of diastatic S. cerevisiae strains of the Mosaic/Beer 2 group. Indeed, both strains possessed functional copies of the STA1 gene responsible for extracellular glucoamylase activity seen in diastatic members of the Beer 2 group. Sequence identity suggested that the same STA1 gene is shared by the chicha and Beer 2 strains despite their genomic dissimilarity, suggesting the possibility of ancient admixture. Pilot-scale brewing trials confirmed the wort fermentation potential of the chicha strains. Beers were characterised by high concentrations of fruity esters and the clove-like compound 4-vinylguaiacol, both of which are typical features of wheat beers and related styles. Sensory trials further confirmed the potential of these strains for brewing, with beers comparing favourably to one produced with a commercial wheat-beer strain under the same conditions. Apart from 4-vinylguaiacol, which is considered an essential flavour compound in wheat beers, no off-flavours were detected in test beers. Results highlight the value of assessing industrial brewing potential of non-European strains associated with traditional cereal-based fermentations.