Saccharomyces eubayanus

Saccharomyces eubayanus, a cryotolerant type of yeast, is most likely the parent of the lager brewing yeast, Saccharomyces pastorianus.[1] [2][3]

Saccharomyces eubayanus
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Saccharomycetes
Order: Saccharomycetales
Family: Saccharomycetaceae
Genus: Saccharomyces
Species:
S. eubayanus
Binomial name
Saccharomyces eubayanus
J.P. Samp., Libkind, Hittinger, P. Gonç., E. Valério, C. Gonç., Dover & M. Johnst.

Lager is a type of beer created from malted barley and fermented at low temperatures, originally in Bavaria. S. eubayanus was first discovered in Patagonia, possibly being an example of Columbian exchange,[4][5] and is capable of fermenting glucose, along with the disaccharide maltose at reduced temperatures.

History

With the emergence of lager beer in the XVth century, S. eubayanus was considered to be the progenitor of S. pastorianus along with S. cerevisiae.[1] Since 1985 the non-cerevisiae ancestor has been contentiously debated between S. eubayanus, and S. bayanus which "is not found outside the brewing environment".[1] Upon the 2011 discovery of S. eubayanus in Argentina and consequential genome analysis, S. eubayanus was found to be 99% genetically identical to S. pastorianus and S. bayanus was dismissed as an ancestor.[1]

First described in 2011, S. eubayanus was discovered in North Patagonia, ecologically associated with Nothofagus spp. (Southern Beech) forests and the parasitic biotrophic fungi Cyttaria spp.[1][2] With discoveries in other parts of the world shortly after in east Asia, the South American origins of S. eubayanus have been challenged by genomic and phylogenetic evidence that suggests a Tibetan origin.[6] The proponents of this theory argue that it "corresponds better with geography and world trade history" given the Eurasian land bridge.[6] Since then, genomic analyses from South America strains have shown reduced genetic diversity suggesting a biogeographical radiation point from Patagonia.[1]

Phylogenetically, S. eubayanus is basal in the Saccharomyces genus, and well-adjusted to the cooler environment of Nothofagus forests, Saccharomyces species with thermo-tolerance are suggested to be derived traits.[1]

Genomics

Population genomic analyses have identified two main populations of S. eubayanus located in Patagonia, Patagonia A and Patagonia B/Holarctic.[1] "These are the closest known wild relatives of the Lager yeasts", comparing sub-genomes, the wild strains are 99.82% and 99.72% identical respectively.[1]

Lager yeasts consist of two distinct lineages, said to have been hybridized from independent events 1000 years ago.[7][8] Type one, called Saaz contains the allotriploid strains with one copy of the S. cerevisiae genome and two copies of the S. eubayanus genome. The second type, Frohberg, houses allotetraploid strains with one full diploid genome copy of S. cerevisiae and S. eubayanus.[7] Saaz strains, which are more physiologically similar to their S. eubayanus parent, are much more efficient at growing in low temperatures, reflecting S. eubayanus' cryotolerant properties.[9] S. eubayanus is said to provide the bottom-fermentation and cold temperature genetics that distinguish this ssp. from the top-brewing and bread making relative S. cerevisiae.

A de novo assembly of the S. eubayanus genome yielded 5,515 protein-coding genes, 4,993 of which were unambiguous 1:1 orthologs to S. cerevisiae, and S. uvarum.[7]

Uses

In 2015, an interspecific hybridization of S. cerevisiae and S. eubayanus was successful in creating novel lager brewing yeasts.[10] However hybrid genomes can result in genetic instability in industrial uses.[11]

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References
  1. .Sampaio JP (2018). "Microbe Profile: Saccharomyces eubayanus, the missing link to lager beer yeasts". Microbiology. 164 (9): 1069–1071. doi:10.1099/mic.0.000677. PMC 6230766. PMID 30175956.
  2. Welsh, Jennifer. "'Missing' Lager Brewing Yeast Discovered in Patagonia". Livescience.com. Retrieved 2011-08-23.
  3. Kaiser, Tiffany. "Lager's Mystery Yeast Discovered in Argentina". Dailytech.com. Retrieved 2011-08-23.
  4. Morrison, David (2014-05-07). "Lager beer and phylogenetic networks". Retrieved 29 October 2014.
  5. Libkind, D.; Hittinger, C.; Valério, E.; Gonçalves, C.; Dover, J.; Johnston, M.; Gonçalves, P.; Sampaio, J. (23 August 2011), "Microbe domestication and the identification of the wild genetic stock of lager-brewing yeast", PNAS, 108 (34): 14539–14544, doi:10.1073/pnas.1105430108, PMC 3167505, PMID 21873232
  6. Bing, J.; et al. (May 2014), "Evidence for a Far East Asian origin of lager beer yeast", Genome Biology, 24 (10): R380–R381, doi:10.1016/j.cub.2014.04.031, PMID 24845661
  7. Baker, EmilyClare; Wang, Bing; Bellora, Nicolas; Peris, David; Hulfachor, Amanda Beth; Koshalek, Justin A.; Adams, Marie; Libkind, Diego; Hittinger, Chris Todd (November 2015). "The Genome Sequence of Saccharomyces eubayanus and the Domestication of Lager-Brewing Yeasts". Molecular Biology and Evolution. 32 (11): 2818–2831. doi:10.1093/molbev/msv168. ISSN 0737-4038. PMC 4651232. PMID 26269586.
  8. Dunn, B.; Sherlock, G. (2008-08-07). "Reconstruction of the genome origins and evolution of the hybrid lager yeast Saccharomyces pastorianus". Genome Research. 18 (10): 1610–1623. doi:10.1101/gr.076075.108. ISSN 1088-9051. PMC 2556262. PMID 18787083.
  9. Gibson, Brian R.; Storgårds, Erna; Krogerus, Kristoffer; Vidgren, Virve (2013-06-29). "Comparative physiology and fermentation performance of Saaz and Frohberg lager yeast strains and the parental speciesSaccharomyces eubayanus". Yeast. 30 (7): 255–266. doi:10.1002/yea.2960. ISSN 0749-503X. PMID 23695993.
  10. Krogerus, Kristoffer; Magalhães, Frederico; Vidgren, Virve; Gibson, Brian (2015-02-15). "New lager yeast strains generated by interspecific hybridization". Journal of Industrial Microbiology & Biotechnology. 42 (5): 769–778. doi:10.1007/s10295-015-1597-6. ISSN 1367-5435. PMC 4412690. PMID 25682107.
  11. Gorter de Vries, Arthur R.; Voskamp, Maaike A.; van Aalst, Aafke C. A.; Kristensen, Line H.; Jansen, Liset; van den Broek, Marcel; Salazar, Alex N.; Brouwers, Nick; Abeel, Thomas (2019-03-29). "Laboratory Evolution of a Saccharomyces cerevisiae × S. eubayanus Hybrid Under Simulated Lager-Brewing Conditions". Frontiers in Genetics. 10: 242. doi:10.3389/fgene.2019.00242. ISSN 1664-8021. PMC 6455053. PMID 31001314.
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