Abstract
Traditional Norwegian Farmhouse ale yeasts, also known as kveik, have captured the attention of the brewing community in recent years. Kveik were recently reported as fast fermenting thermo- and ethanol tolerant yeasts with the capacity to produce a variety of interesting flavor metabolites. They are a genetically distinct group of domesticated beer yeasts of admixed origin with one parent from the “Beer 1” clade and the other unknown. While kveik are known to ferment wort efficiently at warmer temperatures, their range of fermentation temperatures and corresponding fermentation efficiencies, remain uncharacterized. In addition, the characteristics responsible for their increased thermotolerance remain largely unknown. Here we demonstrate variation in kveik strains at a wide range of fermentation temperatures and show not all kveik strains are equal in fermentation performance and stress tolerance. Furthermore, we uncovered an increased capacity of kveik strains to accumulate intracellular trehalose, which likely contributes to their increased thermo- and ethanol tolerances. Taken together our results present a clearer picture of the future opportunities presented by Norwegian kveik yeasts and offer further insight into their applications in brewing.
Highlights
Traditional Norwegian farmhouse ale yeasts, known as kveik, have captured the attention of the brewing community due to their variation from commonly used brewing yeasts (Norland, 1969; Garshol, 2014; Preiss et al, 2018)
We monitored the specific gravities of small-scale wort fermentations at eight different temperatures (Supplementary Figure 1) to gain insight into the temperature-dependent fermentation characteristics of six kveik strains
We provide evidence of strain and temperature-specific variation in fermentation efficiencies of six kveik strains at fermentation temperatures ranging from 12–42◦C
Summary
Traditional Norwegian farmhouse ale yeasts, known as kveik, have captured the attention of the brewing community due to their variation from commonly used brewing yeasts (Norland, 1969; Garshol, 2014; Preiss et al, 2018). Genetic and phenotypic characterizations (Preiss et al, 2018) revealed common signs of domestication and promising beer production attributes [reviewed in Gallone et al (2018)] These included efficient flocculation (>80% of strains analyzed) supported by increased copy number variations (CNVs) of various FLO genes, efficient consumption of major wort sugars with increased CNVs. Variable Thermotolerance and Trehalose Accumulation of maltose and maltotriose metabolic genes (MAL), and homozygous loss-of-function single nucleotide polymorphisms (SNPs) in the genes (PDC1 and FDC1) responsible for producing the phenolic off flavor 4-vinylguaiacol, thereby rendering them phenolic off flavor (POF) negative (Preiss et al, 2018). Phenotypic testing showed remarkable ethanol and thermotolerances for kveik strains, thereby broadening the potential application of these yeasts It is clear from Preiss et al (2018) that these kveik strains, while closely related phylogenetically, are genetically and functionally distinct from each other
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