Biology subjects

Preiss, R.

Publications and source records attributed to Preiss, R..

5 recordsLinked to original sources

bioRxiv2024

European Farmhouse Brewing Yeasts Form a Distinct Genetic Group

The brewing industry is constantly evolving, driven by the quest for novel flavors and fermentation characteristics that cater to evolving consumer preferences. This study explores the genetic and phenotypic diversity of European farmhouse yeasts, traditionally used in rural brewing practices and maintained outside of pure culture industrial yeast selection. We isolated landrace brewing yeast strains from diverse geographical locations across Europe, including Norway, Lithuania, Latvia, Russia, and also included African farmhouse brewing strains from Ghana. Our genomic analysis using long-read and short-read whole genome sequencing uncovered a genetically distinct group that diverges from industrial brewing yeasts. This group, which is closely related to ale brewing strains, is preliminarily named the "European Farmhouse" group and shows greater predicted admixture from Asian fermentation strains. Through genomic and phenotypic analyses, including flavor metabolite analysis via HS-GC-MS, sugar metabolite analysis via HPLC, and wort fermentation analysis, we found a broad spectrum of fermentation capabilities, from rapid and efficient fermentation to unique aroma and flavor compound profiles, potentially offering novel traits for brewing applications. This study highlights the importance of preservation of brewing cultural heritage knowledge and resources including yeast cultures. Key PointsO_LIA large set of geographically diverse farmhouse brewing strains were characterized C_LIO_LINorwegian and Baltic farmhouse brewing strains form a distinct genetic group C_LIO_LIFarmhouse strains show considerable diversity in fermentation and flavour formation C_LI

microbiology↗

bioRxiv2021

Kveik brewing yeasts demonstrate wide flexibility in beer fermentation temperature and flavour metabolite production and exhibit enhanced trehalose accumulation

AO_SCPLOWBSTRACTC_SCPLOWTraditional 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 flavour 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, its range of fermentation temperatures and corresponding flavour metabolites produced, remain uncharacterized. In addition, the characteristics responsible for its 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, flavour metabolite production and stress tolerance. Furthermore, we uncovered an increased capacity of kveik strains to accumulate intracellular trehalose, which likely contributes to its 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.

microbiology↗

bioRxiv2021

Efficient breeding of industrial brewing yeast strains using CRISPR/Cas9-aided mating-type switching

Yeast breeding is a powerful tool for developing and improving brewing yeast in a number of industry-relevant respects. However, breeding of industrial brewing yeast can be challenging, as strains are typically sterile and have large complex genomes. To facilitate breeding, we used the CRISPR/Cas9 system to generate double-stranded breaks in the MAT locus, generating transformants with a single specified mating type. The single mating type remained stable even after loss of the Cas9 plasmid, despite the strains being homothallic, and these strains could be readily mated with other brewing yeast transformants of opposite mating type. As a proof of concept, we applied this technology to generate yeast hybrids with an aim to increase {beta}-lyase activity for fermentation of beer with enhanced hop flavour. First, a genetic and phenotypic pre-screening of 38 strains was carried out in order to identify potential parent strains with high {beta}-lyase activity. Mating-competent transformants of eight parent strains were generated, and these were used to generate over 60 hybrids that were screened for {beta}-lyase activity. Selected phenolic off-flavour positive (POF+) hybrids were further sporulated to generate meiotic segregants with high {beta}-lyase activity, efficient wort fermentation and lack of POF; all traits that are desirable in strains for the fermentation of modern hop-forward beers. Our study demonstrates the power of combining the CRISPR/Cas9 system with classic yeast breeding to facilitate development and diversification of brewing yeast. Key PointsO_LICRISPR/Cas9-based mating type switching was applied to industrial yeast strains C_LIO_LITransformed strains could be readily mated to form intraspecific hybrids C_LIO_LIHybrids exhibited heterosis for a number of brewing-relevant traits C_LI

microbiology↗

bioRxiv2020

Genomic stability and adaptation of beer brewing yeasts during serial repitching in the brewery

Ale brewing yeast are the result of admixture between diverse strains of Saccharomyces cerevisiae, resulting in a heterozygous tetraploid that has since undergone numerous genomic rearrangements. As a result, comparisons between the genomes of modern related ale brewing strains show both extensive aneuploidy and mitotic recombination that has resulted in a loss of intragenomic diversity. Similar patterns of intraspecific admixture and subsequent selection for one haplotype have been seen in many domesticated crops, potentially reflecting a general pattern of domestication syndrome between these systems. We set out to explore the evolution of the ale brewing yeast, to understand both polyploid evolution and the process of domestication in the ecologically relevant environment of the brewery. Utilizing a common brewery practice known as repitching, in which yeasts are reused over multiple beer fermentations, we generated population time courses from multiple breweries utilizing similar strains of ale yeast. Applying whole-genome sequencing to the time courses, we have found that the same structural variations in the form of aneuploidy and mitotic recombination of particular chromosomes reproducibly rise to detectable frequency during adaptation to brewing conditions across multiple related strains in different breweries. Our results demonstrate that domestication of ale strains is an ongoing process and will likely continue to occur as modern brewing practices develop.

evolutionary biology↗

bioRxiv2017

Traditional Norwegian Kveik Yeasts: Underexplored Domesticated Saccharomyces cerevisiae Yeasts

Human activity has resulted in the domestication of Saccharomyces cerevisiae yeasts specifically adapted to beer production. While there is evidence beer yeast domestication was accelerated by industrialization of beer, there also exists a home-brewing culture in western Norway which has passed down yeasts referred to as kveik for generations. This practice has resulted in ale yeasts which are typically highly flocculant, phenolic off flavour negative (POF-), and exhibit a high rate of fermentation, similar to previously characterized lineages of domesticated yeast. Additionally, kveik yeasts are highly temperature tolerant, likely due to the traditional practice of pitching yeast into warm (>30 {degrees}C) wort. Here, we characterize kveik yeasts from 9 different Norwegian sources via PCR fingerprinting, phenotypic screens, lab-scale fermentations, and flavour metabolite analysis using HS-SPME-GC-MS. Genetic fingerprinting via interdelta PCR suggests that kveik yeasts form a lineage distinct from other domesticated yeasts. Our analyses confirm that kveik yeasts display hallmarks of domestication such as loss of 4-vinylguaiacol production and high flocculation, and show superior thermotolerance, ethanol tolerance, fermentation rate, and unique flavour metabolite production profiles in comparison to other ale strains, suggesting a broad industrial potential for this group of yeasts.

microbiology↗