Alternative Saccharomyces interspecies hybrid combinations and their potential for low-temperature wort fermentation.

Jarkko Nikulin,Brian Gibson,Kristoffer Krogerus

doi:10.1002/yea.3246

Abstract

The lager yeast hybrid (Saccharomyces cerevisiae × Saccharomyces eubayanus) possesses two key characteristics that are essential for lager brewing: efficient sugar utilization and cold tolerance. Here we explore the possibility that the lager yeast phenotype can be recreated by hybridizing S. cerevisiae ale yeast with a number of cold‐tolerant Saccharomyces species including Saccharomyces arboricola, Saccharomyces eubayanus, Saccharomyces mikatae and Saccharomyces uvarum. Interspecies hybrids performed better than parental strains in lager brewing conditions (12°C and 12°P wort), with the S. mikatae hybrid performing as well as the S. eubayanus hybrid. Where the S. cerevisiae parent was capable of utilizing maltotriose, this trait was inherited by the hybrids. A greater production of higher alcohols and esters by the hybrids resulted in the production of more aromatic beers relative to the parents. Strong fermentation performance relative to the parents was dependent on ploidy, with polyploid hybrids (3n, 4n) performing better than diploid hybrids. All hybrids produced 4‐vinyl guaiacol, a smoke/clove aroma generally considered an off flavour in lager beer. This characteristic could however be eliminated by isolating spore clones from a fertile hybrid of S. cerevisiae and S. mikatae. The results suggest that S. eubayanus is dispensable when constructing yeast hybrids that express the typical lager yeast phenotype. © 2017 The Authors. Yeast published by John Wiley & Sons, Ltd.

Highlights

Lager beers are brewed with Saccharomyces pastorianus (Gibson and Liti, 2015)
The rise of S. pastorianus to its central role in the brewing industry is presumably due to a fortuitous combination of circumstance and its superior biological properties: the ability to efficiently ferment wort sugars, which has been obtained from a S. cerevisiae parent, and cold tolerance, which has been obtained from a S. eubayanus parent (Gibson et al, 2013)
The phenotype is attributed to the action of the adjacent PAD1 and FDC1 genes, and we have found it to be a feature of the type-strains of all non-S. cerevisiae Saccharomyces species, including S. eubayanus

Summary

Introduction

Lager beers are brewed with Saccharomyces pastorianus (Gibson and Liti, 2015). This bottom-fermenting yeast is an interspecies hybrid of Saccharomyces cerevisiae and Saccharomyces eubayanus (Libkind et al, 2011). This hybridization presumably occurred in Bavaria during the fifteenth or sixteenth centuries, coincident with the rise of low-temperature brewing of lager beer (Meussdoerffer, 2009). The rise of S. pastorianus to its central role in the brewing industry is presumably due to a fortuitous combination of circumstance and its superior biological properties: the ability to efficiently ferment wort sugars, which has been obtained from a S. cerevisiae parent, and cold tolerance, which has been obtained from a S. eubayanus parent (Gibson et al, 2013). Genetic and functional diversity could potentially be increased through the creation of de novo lager yeast hybrids from diverse lineages in the Saccharomyces genus, as long as the requisite characteristics are present

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Results