Changes

Scientists have used genetic modification to create ''S. cerevisiae'' strains that produce various killer toxins that can assist in completing fermentation in the baking, wine, distillation, and beer making processes. These yeasts are able to inhibit undesired yeast contaminants, preventing various off-flavors and other unwanted characteristics in the finished products. Ale and lager strains that have been modified to release these toxins have reportedly retained the positive fermentation and flavor characteristics of the original strains <ref name="Bajaj_2017" />. Branco et al. (2017 and 2019) discovered several strains of ''S. cerevisiae'' that excrete a biocin toxin that is active against several other genera of yeast, including ''Brettanomyces bruxellensis''. The toxin is composed of peptides derived from the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is a protein that serves many different roles in different species of microbes and animals. This toxin is produced by some strains of ''S. cerevisiae'' as they enter the stationary phase after primary fermentation. However, the amount of the toxin needed to inhibit ''B. bruxellensis'' was 10 times the amount that is produced naturally during fermentation. The researchers later genetically modified a strain of ''S. cerevisiae'' to over-produce the toxin, which they named "saccharomycin", at levels required to completely inhibit ''B. bruxellensis'' when co-pitched at a 1:1 ratio (10^5 cells/ml for both). This toxin was also reported to be highly active against ''Hanseniaspora guilliermondii'', ''Kluyveromyces marxianus'', ''Lactobacillus thermotolerans'' (inhibited at 250 μg/ml of toxin), while inhibition of ''Torulaspora delbrueckii'' and ''B. bruxellensis'' required very high amounts of the toxin (500 μg/ml and 1000-2000 μg/ml) <ref>[https://link.springer.com/article/10.1007%2Fs00253-016-7755-6 Antimicrobial properties and death-inducing mechanisms of saccharomycin, a biocide secreted by Saccharomyces cerevisiae. Patrícia Branco, Diana Francisco, Margarida Monteiro, Maria Gabriela Almeida, Jorge Caldeira, Nils Arneborg, Catarina Prista, Helena Albergaria. 2017. DOI: 10.1007/s00253-016-7755-6.]</ref><ref>[https://link.springer.com/article/10.1007/s00253-019-09657-7 Biocontrol of Brettanomyces/Dekkera bruxellensis in alcoholic fermentations using saccharomycin-overproducing Saccharomyces cerevisiae strains. Patrícia Branco, Farzana Sabir, Mário Diniz, Luísa Carvalho, Helena Albergaria, Catarina Prista. 2019.]</ref>.

* [https://www.facebook.com/groups/MilkTheFunk/permalink/2202753476419521/?comment_id=2202936416401227&comment_tracking=%7B%22tn%22%3A%22R0%22%7D Bryan Heit's simple method for testing for killer sensitivity using nothing more than agar plates.]

To do: https://www.researchgate.net/publication/317177883_Biology_of_Killer_Yeast_and_Technological_Implications

====Diastatic strains of ''Saccharomyces cerevisiae''====