Genetics of maltose and maltotriose metabolism in Saccharomyces eubayanus

The first production of alcoholic beverages by fermentation of plant-derived materials occurred many thousands of years ago. In the 15th century, production of lager beer with pale barley malt, soft water and Saaz noble hops, first resulted in pilsner, a clear golden, crispy tasting beer. Today, this type of lager beer is the most produced alcoholic beverage in the world. The yeast responsible for conversion of wort sugars into ethanol, CO2 and aromatic compounds is S. pastorianus, a hybrid of S. cerevisiae and the recently discovered cryotolerant species S. eubayanus. Properties from both parents make S. pastorianus a superior fermenter of brewer’s wort at temperatures below 15 °C. Since S. cerevisiae is not a cryotolerant yeast, the low-temperature performance of S. pastorianus hybrids has been attributed to the S. eubayanus sub-genome. However, the geographical origin of the S. eubayanus sub-genome of S. pastorianus hybrids, as well as its contribution to metabolism of key oligosaccharides in brewer’s wort, is not fully understood. The research described in this thesis therefore focused on the genetics of the metabolism of maltose and maltotriose, two key sugars in brewer’s wort, in S. eubayanus.