Changes

This yeast can 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 STA1+ strains of ''S. cerevisiae''. Additionally, the default level of CuSO₄ which is ~550 ppm (this can vary depending on manufacturer) can inhibit some strains of diastaticu ''diastaticuscerevisiae''; 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'' STA1+ since there is a high occurrence of ''diastaticus'' to most strains 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 diastatic ''diastaticuscerevisiae''. 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). [[Omega Yeast Labs]] reported that a slight alteration to the classic LCYM media recipe had significantly more reliable detection than classic LCYM and the proprietary Weber diastaticus agar for all STA1 positive + strains in Omega's collection, including detecting slow growing strains within 2-3 days and strains with the non-active promoter genes as per Krogerus et al (2019) and limited false positives; see [[Laboratory_Techniques#Saccharomyces|''Saccharomyces'' agar plates]] for the recipe and [https://www.facebook.com/groups/MilkTheFunk/permalink/2874530432575152/ this MTF thread] by Laura Burns from Omega Yeast Labs.

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'' STA1+ 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 diastaticusdiastatic ''cerevisiae''. 06/26/2018.]</ref>. Note that diastatic ''diastaticusS. cerevisiae'' cells look the same under a microscope as regular ''S. cerevisiae'', so cell morphology is not an effective way to identify ''diastaticus'' STA1+ 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, Krogerus 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, however, PCR and qPCR have limited detection rates of 10^-4 and 10^-5 cells (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 Krogerus]).

WY3711 saison yeast has been determined to be STA1+ <ref name="preiss_diastaticus" />. Since yeast cannot be patented, many yeast labs are thought to offer this strain to customers. In the [[Saccharomyces#Commercial_Farmhouse.2FBelgian_Strains_of_Saccharomyces|commercial culture]] lists below where we believe a lab is selling this strain or another strain of ''diastaticus'' diastatic yeast, we note that it is determined or suspected to be ''diastaticus''STA1+.

[https://www.whitelabs.com/yeast-bank/wlp885-zurich-lager-yeast WLP885] are potentially ''diastaticus'' diastatic (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'' diastatic 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'' STA1+ by Kristoffer Krogerus (it is also only one of two known examples of a ''diastaticus'' strain that are not also POF+; the other ''diastaticus'' diastatic 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 diastaticusdiastatic. 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''diastatic.

* [https://www.milkthefunk.live/podcast/2019/10/14/episode-009-diastaticus-with-kristoffer-krogerus-of-beersuregorkcom-and-richard-preiss-of-escarpment-labs MTF "The Podcast" episode on diastaticus STA1+ strains of ''S. cerevisiae'' with Kristoffer Krogerus and Richard Preiss.]

* [http://suigenerisbrewing.com/index.php/2017/11/22/contamination-detection-1/ Sui Generis Brewing blog articles on using practical methods of PCR to identify diastaticus diastatic and other contamination for small breweries.]

* [https://www.reddit.com/r/TheBrewery/comments/5cx15c/qc_folks_any_experience_testing_for_s_diastaticus/ Reddit thread on detecting diastaticusdiastatic ''cerevisiae''.]