New brewing yeasts using native Chilean wine yeasts through an adaptive evolution program

Saccharomyces cerevisiae brewing yeasts have specific genetic characteristics that allow them to survive in malt wort using maltose and maltotriose as the principal carbon source. These sugars are difficult to metabolise for non-brewery Saccharomyces yeasts considering adverse growing conditions: high levels of osmotic stress and low temperatures during the process. Under these conditions, the genetic and phenotypic variability of these yeasts results limited, affecting the diversity of aromas and flavours of the final products. In the present work, we performed an adaptive evolution process by modifying the genomes of 50 native yeasts of Saccharomyces cerevisiae species. We used strains of viticultural origin, collected from different geographical areas of Chile (north, centre and south). After four stages of selection and 600 generations of adaptation, we obtained an evolved strain which can to effectively consume maltose and maltotriose, working with musts that include high osmolarity and low temperatures. At the same time, we performed a sensory analysis finding unconventional aromas associated with the quality of the beer produced. We used bioinformatics tools to contrast the genomes of the evolved and the parental strains finding several differences in their nucleotide composition. We identified differences in genes related to (1) the encoding of maltose and maltotriose transporters, (2) the metabolism of these both sugars, and (3) genes associated with the improvement of the fermentative process. In all the stages, the evolved strain maintained its fermentation capacities by fixing the obtained trait.