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Saccharomyces

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====''Saccharomyces cerevisiae'' var. ''diastaticus''====
''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. This variant can produce extracellular glucoamylase (also called [https://en.wikipedia.org/wiki/Alpha-glucosidase alpha-glucosidase], and is the same enzyme that ''[[Brettanomyces]]'' produces) that can break down the α-1,4 linkages of starches and dextrins releasing glucose that is then fermented by the yeast. When beer containing this yeast is packaged too early, it will continue to slowly ferment dextrins and cause over-carbonation. This enzyme is heat stable and can continue to work on starches and dextrins after 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>. 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 <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). This report is directly contradicted by White Labs regarding their strains with this gene [https://whitelabs.com/yeast-bank/wlp590-french-saison-ale-yeast WLP590], [https://www.whitelabs.com/yeast-bank/wlp099-super-high-gravity-ale-yeast WLP099], and [https://www.whitelabs.com/yeast-bank/wlp045-scotch-whisky-yeast WLP045] (it is likely that the strains reported by other microbiologists to be ''diastaticus'' are the same as these White Labs strains, but this has not been verified). There has been a report by Richard Preiss of [[Escarpment LaboratoryLaboratories]] that WLP570 and 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>. This yeast has also 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''. Documented attenuation percentages above 75% for any strain of ''S. cerevisiae'' is also an indicator that the strain is ''diastaticus'' <ref name="mbaa_diastaticus" />. Var. ''diastaticus'' contamination in breweries has been a recent hot topic, and the source of some contaminations have 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>.
''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>. 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).

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