Changes

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 ''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 diastatic ''cerevisiae''. 06/26/2018.]</ref>. Note that diastatic ''S. cerevisiae'' cells look the same under a microscope as regular ''S. cerevisiae'', so cell morphology is not an effective way to identify ''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]).

=====Commercial Strains=====