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In general, most of the cultures of kveik that have been analyzed contain more than one strain of ''S. cerevisiae'', which was the only species in all of the kveik cultures analyzed by Preiss et al. (2018) except for the Muri kveik. The Muri kveik contains a single isolate of what appears to be a domestic (human produced) hybrid between ''S. cerevisiae'', ''S. eubayanus'', and ''S. uvarum''. Of the 9 kveik cultures analyzed by Preiss et al. (2018), only Muri, Simonaitis, and Stranda contained only one strain of ''S. cerevisiae'', while all of the others contained more than one strain of ''S. cerevisiae'' up to 9 strains in the case of Granvin (see [https://www.frontiersin.org/files/Articles/409253/fmicb-09-02137-HTML-r1/image_m/fmicb-09-02137-t001.jpg this table from the paper]). Genetically, kveik yeast strains form their own group of closely related domesticated ale strains that are a subgroup of the "Beer 1" yeasts (Belgian/Germany/UK/US yeast strains) from the [http://www.cell.com/cell/fulltext/S0092-8674(16)31071-6 Gillons/White Labs (2016)] study that sequenced previously known ale strains (see [http://www.garshol.priv.no/blog/374.html "A family tree for brewer's yeast" by Lars Marius Garshol]). The closest related domesticated strains were 3 German hefeweizen strains, however, this relation is likely just due to both groups being hybrids rather than having any historic connection <ref name="Tyrawa_2017" />.
The individual kveik strains can be divided into two major closely related genetic groups, with the Muri, the Simonatis Lithuanian strain, and a Norwegian bread yeast falling outside of these two groups completely, which arguably categorizes them to not actually be considered "kveik". The two groups of kveik probably originated from two ancestors that were hybrids between a "Beer 1" yeast and wild yeast. Interestingly, some of the kveik cultures have strains from both genetic groups of kveik. For example, Hornindal, Granvin, Laerdal contained strains from both groups of kveik . Overall, their genetic diversity is wider than the genetic diversity of other "Beer 1" subgroups <ref name="Tyrawa_2017" />.
Preiss et al. (2018) also measured the fermentation characteristics of individual kveik strains in their study, the first published data in this regard for kveik. At 86°F (30°C) they found that 11 of the 24 pure strains of kveik outperformed the best control strain (WLP002) in fermentation rate. There was still a very wide range of attenuation rates between the kveik strains (60-90%). Of the 6 strains that had their DNA sequenced, all but one of the Granvin strains fermented maltotriose. All of the strains tested were POF- (meaning they did not produce significant 4-vinylguaiacol phenol) except the Muri strain which is not genetically related to kveik. One of these Sotrdal Stordal Ebbegarden strains also contained a unique mutation on the ''FDC1'' gene that results in the inability to produce phenols and has not been reported before in science. They also found that kveik strains tend to produce fatty acid esters at levels that are typical for other domesticated yeast strains, such as ethyl caproate (pineapple, tropical; threshold 0.21 ppm), ethyl caprylate (tropical, apple, cognac; threshold 0.9 ppm), and ethyl decanoate (apple; threshold 0.2 ppm). The kveik strains studied did not produce high levels of the isoamyl acetate ester (banana) and generally lower levels of the fusel alcohol isobutanol compared WLP001 and WLP002. Strangely, 5 of the 6 strains that were analyzed could form spores, which is not typical for brewers yeast <ref name="Tyrawa_2017" />. The kveik strains studied by Preiss et al. (2018) displayed unique abilities as far as withstanding stress in their environment. Most of the strains at least doubled their growth at 43°C and grew to their maximum potential at 40°C, while the control strains WLP001, WLP002, and WLP029 showed limited growth at those temperatures. This demonstrates kveik's ability to withstand high-temperature fermentations. All strains tested died at 45°C <ref name="Tyrawa_2017" />. Kveik strains were also demonstrated by Preiss et al. (2018) to have a higher tolerance to alcohol than some of the domesticated strains tested (WLP001, WLP002, and WLP029), as well as unique flocculation characteristics. Most of the kveik strains doubled in growth in media with 14% ABV ethanol, and about half of them doubled in growth in 16% ABV ethanol media. Half of the strains of kveik were highly flocculant, but some other strains were very poor flocculators. It is possible that since kveik is a mixed culture of several strains of yeast that the highly flocculant strains assist the others in flocculation thus diminishing for the other strains to evolve flocculation properties <ref name="Tyrawa_2017" />.
===Sigmund Gjernes's Voss Kveik===