{"id":15321,"date":"2018-09-12T13:42:28","date_gmt":"2018-09-12T19:42:28","guid":{"rendered":"http:\/\/appellationbeer.com\/blog\/?page_id=15321"},"modified":"2018-09-12T13:49:17","modified_gmt":"2018-09-12T19:49:17","slug":"the-family-tree-of-yeast","status":"publish","type":"page","link":"https:\/\/appellationbeer.com\/blog\/the-family-tree-of-yeast\/","title":{"rendered":"The family tree of yeast"},"content":{"rendered":"<p><em>This story originally appeared in All About Beer Magazine (May 2017)<\/em><\/p>\n<p>Per K\u00f8lster, who grows his own raw materials to brew beer in the countryside outside Copenhagen, Denmark, headed east several years ago to learn more about traditional farmhouse brewing. In Lithuania he made beer with a local farmer, and when it came time to pitch yeast, they walked to a neighboring farm to collect what they needed. On the way the farmer told K\u00f8lster not to say \u201cthank you\u201d for the yeast. He explained that because no one owns yeast, it must be available to anyone and saying \u201cthank you\u201d would disrupt this system.<\/p>\n<p>Commercial breweries still share yeast, but not as many and not as often. Until 1980 a guard at the Carlsberg brewery gate in Copenhagen handed out small quantities from a \u201cyeast tower\u201d to locals who asked. K\u00f8lster points to this tower as an example of what the word \u201cculture\u201d can mean. It is quite opposite \u201cthe pasteurized approach to culture,\u201d he wrote via email. \u201cDiversity and resilience versus controlled purity and managed intensity.\u201d<\/p>\n<p>It would seem there\u2019s more than one fermentation narrative in brewing these days. Some brewers are intent on exploring diverse flavors often described as sour or funky, the result of spontaneous fermentation, mixed fermentation or fermentation with yeast isolated from the wild. Others expect new pure strains from commercial laboratories to provide diversity. And there are those who are content with the flavor profiles available but are seeking varieties that can broadly be categorized as more efficient.<\/p>\n<p>Serving all of these groups is a genetic family tree for Saccharomyces cerevisiae (one of 1,500 known species of yeast) drawn by research teams from White Labs in California and a Belgian genetics laboratory. Reconstructing what occurred in an older world, the genomic tree\u2014which includes two distinct beer lineages\u2014gives brewers the tools to create a new world.<\/p>\n<p>\u201cTo me, this is just the beginning,\u201d says White Labs founder Chris White. \u201cUnderstanding the DNA is going to be the first part of the story. There is so much information we\u2019ll be sifting through. There is much more to come out of this.\u201d<\/p>\n<p>The first results were published in the scientific journal Cell last September. A headline in The Economist summarized them with typical British restraint: \u201cDomesticated Tipple.\u201d The Washington Post was more expansive: \u201cBeer yeast is tame. Wine yeast is wild. Draw your own conclusions.\u201d The headlines suggest shrinking diversity, but that is not necessarily one of the conclusions of the research. Instead, the authors write that one of the results from differences between beer brewing and winemaking has been a \u201clarge genetic diversity within beer yeasts, while wine yeasts are genetically more homogeneous.\u201d<\/p>\n<p>Researchers in Australia came to a similar conclusion after sequencing the genomes of hundreds of strains of the wine yeast. They discovered yeast strains sold by different companies were almost genetically identical. \u201cOur results show that only a limited branch of the yeast evolutionary tree is currently used in winemaking,\u201d says Anthony Borneman of the Australian Wine Research Institute.<\/p>\n<p>Scientists first sequenced the species of yeast used by brewers and bakers in 1996, determining the order of all 12,057,500 chemical subunits contained in the yeast\u2019s nuclear DNA. It was a step toward sequencing the human genome, a project that took almost a decade and cost about $3 billion by the time it was completed in 2000. Advances in technology since made the process quicker and less expensive, cheap enough that in 2012 Illumina, a San Diego biotechnology company located not far from White Labs, sequenced 96 strains free of charge in order to test new machinery.<\/p>\n<p>\u201cSequencing used to be the hard part. Not anymore,\u201d White says. \u201cNow it\u2019s the time to assemble all the information, to link DNA to phenotype.\u201d<\/p>\n<p>Strains that are closely related genetically may behave quite differently in beer. \u201cThings were more different than I expected,\u201d says Troels Prahl, head of research and development at White Labs. \u201cPart of me was hoping we find only a few (unique varieties), but we did not find many duplicates. The diversity is real. We\u2019re not doing 100 strains every week just because we want to.\u201d <\/p>\n<p>The collaborative research began not long after White Labs started working on this project in 2012. Prahl was speaking at a conference where he learned a Belgian group was also exploring the phenotypic landscape of yeast. Together the two teams sequenced the genomes of 157 industrial S. cerevisiae isolates. This collection includes 102 commercial beer strains, 19 wine strains, 11 spirit strains, seven sake strains, seven strains isolated from spontaneous fermentations, five bioethanol strains, four bread strains and two laboratory strains. (When used to preface beer the word industrial often has negative connotations, but White explains scientists use it to describe yeast selected for distribution for commercial purposes.)<\/p>\n<p>The results illustrate that modern S. cerevisiae yeasts (because they were the focus of the research, from here on they will simply be referred to as yeasts) are distinctly different from wild yeasts because of human selection and, sometimes, geography. Domesticated beer yeasts differ from wild strains, as well as those used for making wine or bread in several significant ways:<\/p>\n<ul>\n<li>They are more efficient at converting maltose (the malt sugar brewers create) into alcohol.\n<li>They flocculate, or settle, better, resulting in beer that is more naturally bright.\n<li>They no longer mate, so are less likely to change when brewers reuse them.\n<li>Most do not produce phenols that may be described as smelling of anything between spicy and electrical tape.<\/ul>\n<p>Although it wasn\u2019t until the 19th century that scientists widely recognized that yeasts were microbes and responsible for fermentation, bakers, brewers and winemakers have been producing bread, beer and wine for thousands of years. They learned that backslopping, an appetizing term that describes a process in which they inoculated unfermented foods or drinks with a portion of fermented product, resulting in predictable fermentations. The report in Cell suggests that growing continuously in a man-made environment led to domestication, and that there are two distinct beer lineages. The first dates to between 1573 and 1604. This coincides historically with a shift from brewing primarily in the home to commercial brewing on a larger, in fact industrial, scale. The second lineage likely originated between 1645 and 1671.<\/p>\n<p>The first, labeled Beer 1, includes three separate, geographically distinct, groups. It originated in the region around what is now Germany and Belgium, spread first to the United Kingdom and then to the United States. The data show that U.S. beer yeasts were imported from Europe during colonization, rather than stemming from indigenous wild U.S. yeast. They are most closely related to British beer yeasts, suggesting that the origin of U.S. brewing strains can be traced to the introduction of beer culture in the United States by early 17th-century British settlers.<\/p>\n<p>\u201cWe deliberately obfuscated which yeast came from which specific brewery, to protect the brewers,\u201d says Kevin Verstrepen, a yeast geneticist at the University of Leuven and the Flanders Institute for Biotechnology, because many brewers \u201cconsider their yeasts something of a top-secret ingredient.\u201d Thus there is no branch of the tree labeled \u201cDuvel\u201d or \u201cSierra Nevada.\u201d And even though the researchers have placed White Labs California Ale Yeast (001) in the Beer 1 group, that doesn\u2019t mean that the other quintessential American ale yeast, Wyeast American Ale (1056), belongs there as well.<\/p>\n<p>However, when Illumina first sequenced yeasts from White Labs, White had them compare a few strains from other labs with those from his own. \u201cCalifornia ale yeast is so important to us we did it for fun,\u201d he says, discussing 001 and 1056. \u201cIt turns out that they are different,\u201d he says. \u201cWhich I\u2019ve been saying all along.\u201d However, when Illumina compared other strains that were said to come from the same industrial sources as White\u2019s, they did turn out to be the same.<\/p>\n<p>Beer 2 yeasts are more stress-tolerant and therefore more successful fermenting higher alcohol beers. They are more closely related to wine yeasts than Beer 1 strains; Beer 2 is placed next to wine in the circular polar format the researchers chose for their phylogenetic tree. Beer 2 includes one-fifth of brewing strains, but unlike Beer 1 they lack geographic structure and contain yeasts originating from Belgium, the United States, the United Kingdom, Germany and Eastern Europe. The research hints that two independent European \u201cdomestic events,\u201d one of which is the origin of both Wine and Beer 2, resulted in the two beer groups.<\/p>\n<p>A certain amount of mystery remains, particularly when it comes to one shared trait. They both contain Phenolic Off Flavor Positive (POF+) yeasts and Phenolic Off Flavor Negative (POF-) yeasts. POF+ yeasts interact with ferulic acids from malted grains to produce 4-vinyl guaiacol, which imparts a clovelike character to beer that is considered positive in German wheat beers (hefeweizens) and some beers of Belgian origin, but otherwise is generally an off flavor.<\/p>\n<p>Wild yeasts are POF+, but the report indicates that medieval brewers must have selected POF- yeast early on, Verstrepen explains, because they were most likely the starting point for domestication. \u201cThe most intriguing questions we cannot answer yet is how they did this,\u201d he says. Every fermentation will contain a few cells that turn POF- because of spontaneous mutation, but those would \u201conly be one or a few cells in a gazillion POF+ cells.\u201d Yet it happened for both the Beer 1 and Beer 2 families.<\/p>\n<p>\u201cThe POF+ yeasts used for some beers seem to have regained their POF characteristics, rather than never losing them, likely because they crossed with a POF+ yeast, or at least received some part of DNA of one,\u201d he says.<\/p>\n<p>Scientists now have what amounts to cut-and-paste tools for altering DNA, so it would be easy enough to flip POF-related genes in any yeast on or off. Two years ago, a microbiologist in the same lab as Verstrepen told The New York Times, \u201cRight now we have a few hundred genetically modified yeast strains patiently waiting in our laboratory\u2019s freezer.\u201d However, the brewing community is firmly united against genetic modification (GM). White Labs, for instance, has banned GM yeasts from its premises, for fear one might accidentally mix with one of its house strains. Verstrepen\u2019s lab has taken a different approach to creating new strains.  Even though its research found 40 percent of commercial beer strains incapable of reproducing sexually, and the others showed dramatically reduced sexual fertility, robots are at work in the lab to breed such strains. \u201cWe have really optimized the conditions so that strains that have very poor sexual cycles can still be persuaded to breed; it is all about tweaking the environment,\u201d Verstrepen says. \u201cI want to stress that this is a very natural process, completely the same as what farmers have been doing and are still doing. But the robots allow us to progress much faster, so that we can hopefully catch up to and even surpass the breeding of crops and livestock.\u201d<\/p>\n<p>The lab has already sold new strains to several breweries, some of them tiny and others multinationals. \u201cWhat customers want changes. This is an example of that. We\u2019re going to get yeast that will create styles we haven\u2019t thought of yet,\u201d White says. However, White Labs did not begin the project with a singular goal to produce new strains. \u201cFor me it was always about the science and information. We wanted to understand these strains better,\u201d he says.<\/p>\n<p>Speaking at Homebrew Con, the annual gathering of American homebrewers, last June in Baltimore, White talked about how quickly understanding was changing. Ten of the S. cerevisiae beer strains in the joint project are used for commercial production of lager beers rather than \u201ctraditional\u201d lager strains, or Saccharomyces pastorianus, which is itself a hybrid of S. cerevisiae and S. eubayanus. Obviously, much more research is needed there as well. Lagers have long constituted the majority of beers brewed, but the origins of their yeast strains have been a mystery. S. eubayanus was only discovered in 2011, first in the wild in Patagonia, but elsewhere since. J\u00fcrgen Wendland, a former yeast biologist at the Carlsberg brewery, recently wrote that \u201cgenome sequencing of lager yeast is only at its early beginnings.\u201d<\/p>\n<p>White put it more dramatically in Baltimore. \u201cWithout unlocking the genetic information, we are still thinking like the 1860s,\u201d he said. He showed a slide with S. cerevisiae-ale yeast-\u201ctop fermenting\u201d on one side and S. pastorianus-lager yeast-\u201cbottom fermenting\u201d on the other. \u201cI\u2019m glad you\u2019re coming to this talk because we are kind of on the brink,\u201d he said. \u201cThis is the old way of talking about this. There is going to be a new way in the next few years.\u201d<\/p>\n<p>*****<\/p>\n<p><b>Sidebar: &#8216;Truly Wild&#8217;<\/b><br \/>\nWhen some brewers talk about \u201cwild yeast,\u201d they include Brettanomyces, although they most often buy it from a laboratory, as well as Lactobacillus and Pediococcus, which are not yeast but bacteria. Jasper Akerboom, who oversees quality control at Lost Rhino Brewing in Virginia and also operated Bright Yeast Labs, is more specific.<\/p>\n<p>He\u2019s isolated more than 100 single strains of Saccharomyces cerevisiae, collected in the wild, that will ferment beer. All share what he calls outspoken character. \u201cI have not found anything that is really mild,\u201d he says. Instead they tend to be \u201cwild,\u201d estery and often needing to ferment at higher temperatures. Most of them do not flocculate very well. They are all POF+, so better suited for brewing saisons than pale ales.<\/p>\n<p>They are much like ones brewers would have chosen 500 years ago\u2014except those existed in a \u201cmixed culture\u201d that included more than one strain of S. cerevisiae as well as Brettanomyces and bacteria. This new interest in wild yeast provides scientists with an opportunity to trace how a strain develops as it becomes domesticated.<\/p>\n<p>In Copenhagen, where Troels Prahl works, White Labs released a strain isolated from apples spontaneously fermented on a remote island off the coast of Denmark. \u201cThe goal is to end with [pure] local yeasts that are suited for brewing and safe for consumption for each of the seasons at a certain habitat or region,\u201d says Prahl. The yeast ferments at a cool, lager-friendly temperature, creating a beer that is \u201cnice and dry, but aromatic like no lager you\u2019ve ever tasted.\u201d <\/p>\n","protected":false},"excerpt":{"rendered":"<p>This story originally appeared in All About Beer Magazine (May 2017) Per K\u00f8lster, who grows his own raw materials to brew beer in the countryside outside Copenhagen, Denmark, headed east several years ago to learn more about traditional farmhouse brewing. In Lithuania he made beer with a local farmer, and when it came time to &#8230; <a title=\"The family tree of yeast\" class=\"read-more\" href=\"https:\/\/appellationbeer.com\/blog\/the-family-tree-of-yeast\/\" aria-label=\"More on The family tree of yeast\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"jetpack_post_was_ever_published":false,"footnotes":""},"class_list":["post-15321","page","type-page","status-publish"],"jetpack_shortlink":"https:\/\/wp.me\/P4wTn-3Z7","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/pages\/15321","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/comments?post=15321"}],"version-history":[{"count":2,"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/pages\/15321\/revisions"}],"predecessor-version":[{"id":15323,"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/pages\/15321\/revisions\/15323"}],"wp:attachment":[{"href":"https:\/\/appellationbeer.com\/blog\/wp-json\/wp\/v2\/media?parent=15321"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}