Beyond Saccharomyces pastorianus for modern lager brews: Exploring non- cerevisiae Saccharomyces hybrids with heterotic maltotriose consumption and novel aroma profile.

Non-domesticated, wild yeasts have promising characteristics for beer diversification, particularly when used in the generation of interspecific hybrids. A major motivation for the current work was the question whether attractive novel interspecific hybrids can be created for the production of exotic lager beers without using the genomic resources of the ale yeast . Importantly, maltotriose utilization is an essential characteristic typically associated with domesticated ale/lager brewing strains. A high-throughput screening on nearly 200 strains representing all eight species of the genus was conducted. Three strains were able to aerobically grow on maltotriose as the sole carbon source, a trait until recently unidentified for this species. Our screening also confirmed the recently reported maltotriose utilization of the strain D5095. Remarkably, hybrids between a maltotriose-utilizing or strain and the maltotriose-negative strain CBS 12357 displayed heterosis and outperformed both parents with regard to aerobically utilizing maltotriose as the sole source of carbon. Indeed, the maximum specific growth rates on this sugar were comparable to the well-known industrial strain, CBS 1513. In lager brewing settings (oxygen-limited), the new hybrids were able to ferment maltose, while maltotriose was not metabolized. Favorable fruity esters were produced, demonstrating that the novel hybrids have the potential to add to the diversity of lager brewing.