13,586
edits
Changes
added Kris's new detection method for diastatic yeast
Detection of ''STA1+'' strains of ''S. cerevisiae'' as a contaminant can be difficult. While using PCR to detect the ''STA1'' gene and the promoter gene, the presence of the promoter gene alone does not completely explain the wide variance of diastatic power between strains. Additionally, PCR genotyping is sucseptable to user error or DNA detection from dead cells. Detection of the presence of starch degrading enzymes can come from other contaminants such as ''Brettanomyces'' <ref name="Omega_diastaticus_2020" />. Some agar media products and even starch/dextrin materials have been suspected to contain small amounts of glucose or other simple sugar contaminants that can support the growth of non-diastatic yeasts <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/3308119659216225/ Lance Shaner and Joshua Mayers. Milk The Funk Facebook thread on Omega Yeast's STA1+ detection methods. 03/04/2020.]</ref>. [[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 diastatic agar for all ''STA1+'' 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, as well as their [https://omegayeast.com/news/improved-functional-assays-and-risk-assessment-for-sta-strains-of-saccharomyces-cerevisiae associated peer reviewed study on recommended detection methods)] <ref>[https://www.tandfonline.com/doi/full/10.1080/03610470.2020.1796175 Laura T. Burns, Christine D. Sislak, Nathan L. Gibbon, Nicole R. Saylor, Marete R. Seymour, Lance M. Shaner & Patrick A. Gibney (2020) Improved Functional Assays and Risk Assessment for STA1+ Strains of Saccharomyces cerevisiae, Journal of the American Society of Brewing Chemists, DOI: 10.1080/03610470.2020.1796175 .]</ref>. A summary of the Omega Yeast Lab detection methodology findings by Lance Shaner is available [https://www.facebook.com/groups/MilkTheFunk/permalink/3308119659216225/ here on MTF]. Escarpment Labs built upon the work by Burns et al. and developed a modified version of the Omega LCYM, and they reported it to have less false positives for non-diastatic strains and it has reportedly been used for growing beer strains of ''Brettanomyces'' and ''Pichia''. See the [[Laboratory_Techniques#Saccharomyces|Escarpment SCCM media]].
In 2022, Ida Uotila and Kristoffer Krogerus developed a simple detection technique that only requires basic lab equipment (pipettes, centrifuge, and heat block), gives results from beer or yeast samples in 75 minutes, and with accuracy as good as traditional PCR-based methods. The test result can be visualized on a lateral flow strip. For more information, see [https://www.biorxiv.org/content/10.1101/2022.11.23.517627v1 their published paper] ([https://www.facebook.com/groups/MilkTheFunk/posts/6360775983950562 associated MTF thread]).
=====Commercial Strains=====