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update to diastaticus
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''Saccharomyces cerevisiae'' var. ''diastaticus'' is a variant of ''S. cerevisiae'' that can ferment certain types of starches and dextrins, and has been identified as a contaminant in breweries and is responsible for a few large recalls. Although these strains do not produce flavors that are considered unpleasant(although all ''diastaticus'' strains tested in one study produced phenols <ref name="Meier-Dörnberg_2018">[https://www.ncbi.nlm.nih.gov/pubmed/29518233 Saccharomyces cerevisiae variety diastaticus friend or foe? Spoilage potential and brewing ability of different Saccharomyces cerevisiae variety diastaticus yeast isolates by genetic, phenotypic and physiological characterization. Meier-Dörnberg T, Kory OI, Jacob F, Michel M, Hutzler M. 2018. doi: 10.1093/femsyr/foy023.]</ref>), it is often viewed as a contaminant because of its ability to over-attenuate. A survey of contamination reports in the last ten years at European breweries (50% of which were German breweries, which are obligated by law to report such contaminations) found an increase in reports from 2015, 2016, and 2017. 71% of the contamination incidents originated from the packaging systems (bottling/canning lines). These contaminations were tracked down to the filler environment and/or biofilms in the pipework system of the filler which stemmed from hygienic problems. As such, sometimes contaminations can be sporadic with some bottles being contaminated while others are not. The other 29% of the contaminations were tracked down to primary contaminations in the brewhouse, fermentation cellar, and storage cellar <ref name="Meier-Dörnberg">[https://www.mbaa.com/publications/tq/tqPastIssues/2017/Pages/TQ-54-4-1130-01.aspx Incidence of Saccharomyces cerevisiae var. diastaticus in the Beverage Industry: Cases of Contamination, 2008–2017. Tim Meier-Dörnberg, Fritz Jacob, Maximilian Michel, and Mathias Hutzler. 2017. MBAA Technical Quarterly; http://dx.doi.org/10.1094/TQ-54-4-1130-01.]</ref>.
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 produces 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>. However, it has been reported by some microbiologists that most (if not all) 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). When beer containing this yeast is packaged too early, it will continue to slowly ferment dextrins and cause over-carbonation. When pitching a proper cell count or pitching rate of a ''diastaticus'' yeast strain into the wort, it will fully ferment as quickly or nearly as quickly as any other brewers yeast. ''S. cerevisiae'' var ''diastaticus'' can grow at 37°C and can also remain viable at refrigeration temperatures <ref>[http://www.ebc2017.com/inhalt/uploads/P095_Begrow.pdf Wade Begrow. "Recent notable microbiological contaminations of craft beer in the United States". Presentation poster at EBC 2017. Retrieved 11/19/2017.]</ref>. 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 problem of slow fermentation in already packaged beer is only a concern when ''diastaticus'' is introduced as a very small cell count, for example as an accidental contamination <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1982499288444942/?comment_id=1983013578393513&comment_tracking=%7B%22tn%22%3A%22R1%22%7D Caroline Whalen Taggart. Milk The Facebook post on how quickly diastaticus ferments. 02/09/2018.]</ref>. The enzyme produced by these strains is heat stable and can continue to work on starches and dextrins even after the yeast is killed by heat pasteurization <ref>[https://www.mbaa.com/publications/tq/tqPastIssues/1983/Abstracts/tq83ab19.htm Factors That Control the Utilization Of Wort Carbohydrates by Yeast. G. G. Stewart, I. Russell, and A. M. Sills. MBAA Technical Quarterly, Vol. 20, No. 1, 1983.] </ref>.
Var. ''diastaticus'' contamination in breweries has been a recent hot topic, and the source of some contaminations has been suspected to come from certain yeast suppliers (namely 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">[https://www.ncbi.nlm.nih.gov/pubmed/29518233 Saccharomyces cerevisiae variety diastaticus friend or foe? Spoilage potential and brewing ability of different Saccharomyces cerevisiae variety diastaticus yeast isolates by genetic, phenotypic and physiological characterization. Meier-Dörnberg T, Kory OI, Jacob F, Michel M, Hutzler M. 2018. doi: 10.1093/femsyr/foy023.]</ref>. 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''. 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]]).
WY3711 saison yeast, which originated from Basserie Thiriez, has been determined to be this subspecies <ref name="preiss_diastaticus" />. In the [[Saccharomyces#Commercial_Farmhouse.2FBelgian_Strains_of_Saccharomyces|commercial culture]] lists below where we believe a lab is selling this strain of yeast or might be selling this strain of yeast, we note that it is determined/suspected to be ''diastaticus''. The Belle Saison strain from Lallemand is killer neutral, which means that killer wine strains will not kill it (it is not verified if Belle Saison is the same as WY3711/Thiriez, although it is suspected to be).