Maltose and maltotriose metabolism in brewing-related Saccharomyces yeasts

haploid S. cerevisiae laboratory strain of the CEN.PK family. The performance of the constructed hybrid, strain IMS0408, was then compared to those of its parents in anaerobic batch cultures grown on different media and at different temperatures. While S. eubayanus displayed significantly higher growth rates than S. cerevisiae in anaerobic batch cultures below 25 °C, the laboratory hybrid IMS0408 performed as well as the best parent or even better at most tested temperatures. In contrast to its S. eubayanus parent, the hybrid strain was further able to consume maltotriose, the second most abundant sugar in wort, in cultures grown on sugar mixtures. This observation showed how acquisition of the S. cerevisiae genome contributed an important brewing related characteristic of the hybrid. The hybrid strain IMS0408 showed a best parent heterosis in two major characteristics that are relevant in the brewing environment. This heterosis illustrates how an early, spontaneous S. pastorianus lager brewing hybrid might have outcompeted other Saccharomyces species, including its parental ones, under the low-temperature, high-maltotriose conditions of lager fermentation processes.