M. Eng (Biotech.) Frederico Magalhães defended his PhD thesis Harnessing heterosis: enhancing industrial yeast functionality through interspecific hybridisation on 5 December. Interspecific hybridisation was shown to improve low-temperature fermentation performance without compromising product quality in beer, cider and wine.
Industrial fermentation conditions, such as those found in beer, cider and winemaking, can prove very challenging for the yeast. Such conditions require the yeast to consume large quantities of complex sugars in often lower than optimal temperatures. However, yeast can naturally mate and form hybrids, allowing the possibility to combine the best properties of two or more yeast species into one.
In the thesis, the influence of genetic material for 2 different species on maltose and maltotriose utilisation rates was studied. Moreover, with the discovery of S. eubayanus, the cold tolerant parent of the lager yeast, the first new lager strains in 500 years were generated by mating with an ale strain. The properties of S. eubayanus, such as cold tolerance and fructose utilisation were explored by creating additional hybrid yeast for use in cider and winemaking. These new strains can ferment at a wide range of temperatures. Importantly, the low temperature range reduces the risk of contaminations, possibly allowing for the reduction of the use of sulphates. The tolerance to the higher range of temperatures facilitates large-scale production in active dry yeast form. The wines and ciders produced with these strains are characterized by increased aromatic complexity. In addition, the production of unpleasant sulphur volatiles was eliminated.
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