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→Debaryomyces spp.
''Debaryomyces'' is a genus of yeast commonly referred to as a spoilage yeast <ref>[https://en.wikipedia.org/wiki/Debaryomyces Wikipedia. Debaryomyces. Retrieved 09/03/2015.]</ref>. The non-pathogenic species ''D. hansenii'' is commonly found in cheese and is an osmotolerant, halotolerant, and xerotolerant (tolerant high amounts of salt and sugar, and low amounts of water) <ref>[https://en.wikipedia.org/wiki/Debaryomyces_hansenii Wikipedia. Debaryomyces hansenii. Retrieved 09/03/2015.]</ref>. Debaryomyces are associated with natural fermentation, and tend to develop during the maturation of beer <ref name="Brewlab_debaryomyces">[https://www.brewlab.co.uk/news/the-original-flag-porter-story "The Original Flag Porter Story". Brewlab website. 01/20/2017. Retrieved 12/08/2017.]</ref>. Many species of ''Debaryomyces'' have been to biotransform monoterpenes found in hop oils (see [[Hops#Hop_Derived_Compounds_In_Beer_and_Biotransformations|Hop Biotransformations]]).
Recently it was found living cells of a ''Debaryomyces'' species in a [https://www.brewlab.co.uk/news/the-original-flag-porter-story bottle of porter] found in a shipwreck under the English Channel that was dated to 1825. It is currently unknown how this yeast might have affected the flavor of the historical porter, but the characterization of this yeast is underway by Brewlab in the UK <ref name="Brewlab_debaryomyces" /><ref>[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.641 Thomas, K., Ironside, K., Clark, L., and Bingle, L. (2021) Preliminary microbiological and chemical analysis of two historical stock ales from Victorian and Edwardian brewing. J. Inst. Brew., 127: 167– 175. https://doi.org/10.1002/jib.641.]</ref>. See also [https://www.facebook.com/groups/MilkTheFunk/posts/5338230866205084/?comment_id=5338705966157574 this post by Gareth Young] on tasting one of these bottles, and his potential attempts to culture microbes from other bottles.
Some species of ''Debaryomyces'' can produce exopolysaccharides (EPS), which are extracellular (produced and expelled outside of the cell) polymers of monosaccharides connected by glycosidic bonds with a degree of polymerization higher than 10. EPS assists in producing biofilms for microorganisms. It is possible that EPS from yeast could make beer "ropy" or "sick", similar to [[Pediococcus]] <ref name="Gientka_2015">[https://www.researchgate.net/publication/283498621_Exopolysaccharides_from_yeast_insight_into_optimal_conditions_for_biosynthesis_chemical_composition_and_functional_properties_-_review?fbclid=IwAR1X6Y0rnquoF6SD-eH9m6EWpLIefgZJFUJK51NJYBooJWngxEVS2aR3PKE Exopolysaccharides from yeast: insight into optimal conditions for biosynthesis, chemical composition and functional properties - review. Iwona Gientka, Stanisław Błażejak, Stanisław Błażejak, Lidia Stasiak, Lidia Stasiak, Anna Chlebowska-Śmigiel, Anna Chlebowska-Śmigiel. 2015.]</ref>.