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This variant of ''S. cerevisiae'' can produce extracellular glucoamylase (also called [https://en.wikipedia.org/wiki/Alpha-glucosidase alpha-glucosidase], which is the same enzyme that ''[[Brettanomyces]]'' produces to break down starches and dextrins). This enzyme is released outside of the cell and can break down the α-1,4 linkages of starches and dextrins releasing glucose that is then fermented by the yeast. The capability to produce this enzyme is encoded by the ''STA1'', ''STA2'', or ''STA3 '' genes. Not all strains containing one of these genes produce the glucoamylase enzyme or are as effective as others at metabolizing dextrins <ref>[https://link.springer.com/article/10.1007%2FBF00365634 STA10: A gene involved in the control of starch utilization by Saccharomyces. Julio Polaina, Melanie Y. Wiggs. 1983.]]</ref><ref>[http://onlinelibrary.wiley.com/doi/10.1002/yea.1102/full Structural analysis of glucoamylase encoded by the ''STA1 '' gene of Saccharomyces cerevisiae (var. diastaticus). Ana Cristina Adam, Lorena Latorre-Garcia, Julio Polaina. 2004.]</ref>. It has been reported by some microbiologists that most brewing strains that contain ''STA1'', ''STA2'', or ''STA3 '' do produce the glucoamylase enzyme <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1935201836508021/?comment_id=1936604203034451&reply_comment_id=1937166892978182&comment_tracking=%7B%22tn%22%3A%22R7%22%7D Richard Preiss. Milk the Funk thread about ''STA1 '' gene correlation to glucoamylase production. 12/31/2017.]</ref><ref name="mbaa_diastaticus">[http://masterbrewerspodcast.com/068-diastaticus-part-1 Matthew Peetz of Inland Island and Tobias Fischborn of Lallemand. "Master Brewers Association Podcast" 12/25/2017.]</ref>(~16 mins). A study that surveyed 18 strains of ''diastaticus'' that contain the STA gene found that only one was not able to ferment dextrins <ref name="Meier-Dörnberg_2018" />. Richard Preiss has also reported that WLP351 has the STA gene, but is not able to ferment dextrins <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1888017211226484/?comment_id=2013050695389801&reply_comment_id=2013355312026006&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Richard Preiss. Milk The Funk Facebook group thread on diastaticus strains that do not ferment dextrins. March 2018.]</ref>. Krogarus et al. (2019) discovered that a region of genes just upstream of the ''STA1 '' gene (promoter) called 1162 bp is missing in strains that test positive for the ''STA1 '' gene but do not test positive for fermenting starches, dextrins, or secreting the enzyme. They were able to demonstrate that this region is needed for the ''STA1 '' gene to become effective. They also discovered that ''STA1 '' gene is found in the Beer 2 group of yeast (see [[Saccharomyces#History_of_Domestication|History of Domestication]] above), and wild yeast strains do not carry the ''STA1 '' gene. Coincidentally, Beer 2 yeast strains lack the genes that the Beer 1 yeast strains do for fermenting maltotriose, yet Beer 2 yeasts ferment maltotrios just fine; it was discovered by Krogarus et al. (2019) that the ''STA1 '' gene allows the Beer 2 yeasts to ferment maltotriose (although this exact mechanism is not known yet) <ref name="krogarus_2019">[https://www.biorxiv.org/content/10.1101/654681v1 A deletion in the ''STA1 '' promoter determines maltotriose and starch utilization in ''STA1+ '' Saccharomyces cerevisiae strains. Kristoffer Krogerus, Frederico Magalhães, Joosu Kuivanen, Brian Gibson. 2019. DOI: https://doi.org/10.1101/654681.]</ref>. For more details on the Krogarus et al. (2019) study, see [http://beer.suregork.com/?p=4068 this Suregork Loves Beer blog post] and [https://www.facebook.com/groups/MilkTheFunk/permalink/2697088176986046/ this MTF thread posted by Kristoffer Krogarus].

Var. ''diastaticus'' contamination in breweries has been a recent hot topic. These strains are effectively eliminated by standard cleaning and sanitation practices, although inadequate cleaning hygiene can lead to biofilm formation which makes them more resistant to cleaning regiments <ref name="Meier-Dörnberg" />. The source of some contaminations has also been suspected to potentially come from yeast suppliers, although there is no known percentage of infections which originate from yeast suppliers versus poor hygiene in the brewery. For example, a lawsuit by Left Hand Brewing Co. accused White Labs as being the source for the brewery's ''diastaticus'' contamination issues (see also [https://www.whitelabs.com/diastaticus this statement by White Labs]) <ref>[https://www.courthousenews.com/wp-content/uploads/2017/11/Left-Hand-v-White-Labs-COMPLAINT.pdf District Court, Boulder County, Colorado. Case Number 2017CV31132. Filed 11/14/2017.]</ref>. Detection of ''S. cerevisiae'' var. ''diastaticus'' as a contaminant can be difficult. Contamination usually occurs as a secondary contaminant (meaning in the packaging system), and can come from contact with beer lines, by air circulation in the area of the packaging equipment, or by insufficient heat treatment of the packaging line. Since a very small number of cells is enough to contaminate beer, contaminations can be sporadic with only a percentage of bottles being contaminated <ref name="Meier-Dörnberg_2018" />. Documented attenuation percentages above 75% for any strain of ''S. cerevisiae'' is also an indicator that the strain could be ''diastaticus'', however, some non-diastaticus strains can also attenuate higher than 75%, so this indicator is not a reliable method to be sure that a given strain is ''diastaticus'' <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2004689559559248/?comment_id=2004695002892037&reply_comment_id=2005133672848170&comment_tracking=%7B%22tn%22%3A%22R1%22%7D Adi Hastings. Milk The Funk Facebook Group post on non-diastaticus strains with high attenuation. 02/27/2018.]</ref><ref name="mbaa_diastaticus" />. Often this contamination can only be detected by sensory testing weeks after packaging. This yeast has reportedly been detected using [http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1981.tb04005.x/pdf LCSM agar plates], although other species of wild ''Saccharomyces'' yeast can grow on this media <ref name="mbaa_diastaticus" />(~18 mins) and PCR DNA analysis is required to give a positive identification of ''diastaticus''. Additionally, the default level of CuSO₄ which is ~550 ppm (this can vary depending on manufacturer) can inhibit some strains of ''diastaticus''; Wade Begrow of Founders Brewing Co. recommends diluting the LCSM media with a basic malt media so that the CuSO₄ reaches around 200 ppm, or using LCSM plates modified with a gradient of CuSO₄ <ref name="Begrow_MBAA" /> (~22 mins in). Adding p-coumaric acid or other cinnamic acids to the LCSM agar media which can then test for POF+ yeast and then confirmed for the presence of phenols via a gas chromatography or some other method can also be used to indicate that a yeast might be ''diastaticus'' since there is a high occurrence of ''diastaticus'' to produce phenols from these cinnamic acids <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2149139905114212/?comment_id=2150763631618506&reply_comment_id=2158975484130654&comment_tracking=%7B%22tn%22%3A%22R0%22%7D Shawn Savuto and linked references. Milk The Funk Facebook book post on POF+ correlation with ''diastaticus''. July 2018.]</ref> (see also [https://www.facebook.com/groups/MilkTheFunk/permalink/1903290776365794/ this MTF thread] on using cinnamic acids to identify phenolic off flavor strains). Cheaper methods of doing PCR are recently becoming available, and could help breweries with smaller budgets sufficiently detect this as a contaminant (see [[Laboratory_Techniques#PCR.2FqPCR|PCR Lab Techniques]]). A recent study used agar plates with 15 g/L^-1 of starch as the only nutrient with 40 mg/L^-1 bromophenol blue in anaerobic conditions to detect the fermentation of starch (a pH drop from 5.2 to 4.6-3.0 will change the color of the agar plate to blue/violet). For some of the slower growing strains, 14 days were required to verify that they were ''diastaticus'' while other strains grew as quickly as two days and most strains grew after five days. The yeast cells had to be thoroughly washed of all other carbohydrate material and starved in order to avoid false positives. Using dextrin agar plates instead of starch also led to false positives <ref name="Meier-Dörnberg_2018" />. This starch media has been recommended by Richard Preiss from [[Escarpment Laboratories]] and Justin Amaral from [[Mainiacal Yeast]] <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2149139905114212/?comment_id=2150763631618506&comment_tracking=%7B%22tn%22%3A%22R%22%7D Richard Preiss and Justin Amaral. Milk The Funk Facebook thread on plate media for diastaticus. 06/26/2018.]</ref>. Note that ''diastaticus'' cells look the same under a microscope as regular ''S. cerevisiae'', so cell morphology is not an effective way to identify ''diastaticus'' strains <ref name="Begrow_MBAA">[https://www.mbaa.com/education/webinars/Pages/webcast.aspx?vid=diastaticus Wade Begrow. "S. cerevisiae var. diasttaicus". MBAA webinar. July 2018.]</ref> (~8 minutes in). Other methods of detection include using a Durham tube/fermentation tube test to see if the beer produces CO² after fermentation, although this method does not identify the cause of the additional fermentation <ref name="Begrow_MBAA" /> (~18 mins in). More recently, Krogarus et al. (2019) developed more precise PCR primers to detect ''STA1 '' active, ''STA1 '' non-active, and non-''STA1 '' based on their discovered role of an ''STA1 '' promoter called ''1162 bp'' that is required for the ''STA1 '' gene to be effective at producing the glucoamylase enzyme (see [http://beer.suregork.com/?p=4068 this Suregork Loves Beer blog post] and [https://www.facebook.com/groups/MilkTheFunk/permalink/2697088176986046/ this MTF thread posted by Kristoffer Krogarus]).

[https://www.whitelabs.com/yeast-bank/wlp885-zurich-lager-yeast WLP885] are potentially ''diastaticus'' (thanks to [https://gist.github.com/thcipriani/c303e39d6e8044307fa292cac6de6bd6 "thcipriani's" python script]), however, they do not designate if these strains actually ferment dextrins. Some hints as to which other White Labs products might also be ''diastaticus'' have been deduced from the [[Saccharomyces#History_of_Domestication|Gallone et al. study]] which published DNA sequencing on most of the yeast strains in the White Labs bank. However, the codes used in the Gallone paper for each strain of yeast were not defined as far as which White Labs products they correspond to. Some of the codes have been speculated on which White Labs strains they might refer to (see [[Saccharomyces#History_of_Domestication|History of Domestication]] above). The strains from the Gallone paper that appear to contain ''STA1 '' are Beer002, Wine019, Beer092 and Beer059. The Beer059 code might correspond to WLP026 according to this speculative [https://www.facebook.com/groups/MilkTheFunk/permalink/1400297539998456/?comment_id=1908170505877821&comment_tracking=%7B%22tn%22%3A%22R0%22%7D table], which has had reports of high attenuation and has been independently confirmed to be ''diastaticus'' by Kristoffer Krogerus (it is also only one of two known examples of a ''diastaticus'' strain that are not also POF+; the other ''diastaticus'' strain that is POF- is WLP644) <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2095461573815379/?comment_id=2096044890423714&reply_comment_id=2105481916146678&comment_tracking=%7B%22tn%22%3A%22R%22%7D Kristoffer Krogerus. Milk The Funk Facebook thread on WLP026. 05/25/2018.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1400297539998456/?comment_id=1909596632401875&reply_comment_id=1910328215662050&comment_tracking=%7B%22tn%22%3A%22R9%22%7D MTF thread on ''STA1 '' gene and White Labs strains that might have it or not. Milk The Funk Facebook group. 12/07/2017.]</ref>. There has been a report by Richard Preiss of [[Escarpment Laboratories]] that WLP570 (confirmed by White Labs) and [https://www.whitelabs.com/yeast-bank/wlp585-belgian-saison-iii-ale-yeast WLP585] both have the ''STA1 '' gene, but it takes weeks before they hyper-attenuate <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1888017211226484/?comment_id=1911782002183338&reply_comment_id=1982274298467441&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Richard Preiss. Milk The Funk Facebook group post on WLP570 and WLP585 being diastaticus. 02/08/2018.]</ref>. Other yeast labs such as [http://www.lallemand.com/ Lallemand], [https://inlandislandyeast.com/yeast-library/inis-491-saison-french/ Inland Island], [https://www.escarpmentlabs.com/strains Escarpment Labs], and [https://www.theyeastbay.com The Yeast Bay] also list which strains they offer are ''diastaticus''.

* [http://beer.suregork.com/?p=4068 Kristopffer Krogarus explains his discovery of the ''STA1'' promoter gene that explains why some ''STA1'' positive strains do not effectively ferment starches or dextrins, as well as the occurence of this promoter gene within the Beer 2 yeast group and lack of it in wild yeast, new PCR primers for detecting active vs non-active ''STA1'' strains.]* [https://www.escarpmentlabs.com/single-post/2018/10/16/Demystifying-diastaticus-part-1 Escarpment Labs PCR protocol for testing for ''STA1'', including details on the limitations of PCR testing] and [https://www.escarpmentlabs.com/single-post/2018/10/22/Demystifying-diastaticus-part-2 Part 2, identifying using starch agar plating and LCSM plating.]