Yeast two‐ and three‐species hybrids and high‐sugar fermentation

Abstract

Summary The dominating strains of most sugar‐based natural and industrial fermentations either belong to Saccharomyces cerevisiae and Saccharomyces uvarum or are their chimeric derivatives. Osmotolerance is an essential trait of these strains for industrial applications in which typically high concentrations of sugars are used. As the ability of the cells to cope with the hyperosmotic stress is under polygenic control, significant improvement can be expected from concerted modification of the activity of multiple genes or from creating new genomes harbouring positive alleles of strains of two or more species. In this review, the application of the methods of intergeneric and interspecies hybridization to fitness improvement of strains used under high‐sugar fermentation conditions is discussed. By protoplast fusion and heterospecific mating, hybrids can be obtained that outperform the parental strains in certain technological parameters including osmotolerance. Spontaneous postzygotic genome evolution during mitotic propagation (GARMi) and meiosis after the breakdown of the sterility barrier by loss of MAT heterozygosity (GARMe) can be exploited for further improvement. Both processes result in derivatives of chimeric genomes, some of which can be superior both to the parental strains and to the hybrid. Three‐species hybridization represents further perspectives.

Diversity and Postzygotic Evolution of the Mitochondrial Genome in Hybrids of Saccharomyces Species Isolated by Double Sterility Barrier

“…The species of the genus are reproductively isolated by a postzygotic double sterility barrier (Pfliegler et al, 2012). Under laboratory conditions any of the Saccharomyces species can form hybrids with any other species of the genus (e.g., Banno and Kaneko, 1989;Hawthorne and Philippsen, 1994;Naumov, 1996;Marinoni et al, 1999;Lorenz et al, 2002;Antunovics et al, 2005;Solieri et al, 2005;Rainieri et al, 2008;Bellon et al, 2011Bellon et al, , 2013Garcia Sanchez et al, 2012;Pérez-Través et al, 2014;Lopandic et al, 2016;Karanyicz et al, 2017;Nikulin et al, 2018;Peris et al, 2019;Sipiczki, 2019;Lairón-Peris et al, 2020). The interspecies hybrids are viable but sterile because cannot produce functional gametes (ascospores).…”

MAT heterozygosity and the second sterility barrier in the reproductive isolation of Saccharomyces species

“…As both 10-1653 and 10-1651 were ura3 , the kudvarum hybrids were auxotrophic for uracil. To produce three-species cekudvarum hybrids with the method described in Sipiczki ( 2019 ), one of them (II/6) was mass-mated with the heterothallic leucine-auxotrophic S. cerevisiae strain 10-170. Although the kudvarum parent proved to be inactive in the mating tests, we presumed that their mating block was not absolute and mating-competent allodiploid cells might occasionally be produced during vegetative propagation.…”

Never Change a Brewing Yeast? Why Not, There Are Plenty to Choose From

“…In addition, hybrids can also benefit from a less well-understood effect called heterosis or hybrid vigor, where the resulting hybrid shows a greater fitness than one would expect based on each parental strain ( Lindegren et al, 1953 ; Hebly et al, 2015 ; Bernardes et al, 2017 ). Although hybrids have a huge potential for industrial use, they themselves are usually less suitable for performing genetic crosses since most strains will suffer from hybrid sterility, resulting in very low numbers of viable progeny with a clear mating type ( Sipiczki, 2018 , 2019 ; Ono and Greig, 2020 ; Sipiczki et al, 2020 ). While there were attempts to create novel “lager” strains by crossing meiotic offspring of “lager” yeasts already in the early 1980s ( Gjermansen and Sigsgaard, 1981 ), it was the identification of S. eubayanus that changed the concept of creating novel “lager” yeasts significantly.…”