{"id":553,"date":"2015-05-05T14:36:00","date_gmt":"2015-05-05T14:36:00","guid":{"rendered":"http:\/\/suigenerisbrewing.com\/index.php\/2015\/05\/05\/purifying-yeast-from-infected-cultures-part-1\/"},"modified":"2017-09-15T18:04:36","modified_gmt":"2017-09-15T18:04:36","slug":"purifying-yeast-from-infected-cultures-part-1","status":"publish","type":"post","link":"https:\/\/suigenerisbrewing.com\/index.php\/2015\/05\/05\/purifying-yeast-from-infected-cultures-part-1\/","title":{"rendered":"Purifying Yeast from Infected Cultures – Part 1"},"content":{"rendered":"\n\n\n\n
<\/a><\/td>\n<\/tr>\n
Mixed Saccharomyces<\/i>\u00a0(large ovoid cells) and Brettanomyces<\/i>
\n(elongated cells) yeast culture contaminated with cocci
\n(top-centre “string”) and rod-shaped bacteria<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

One of the most requested topics I receive is how to clean up an infected yeast sample. I’ve alluded to the use of streak plates<\/a>, and basic identification of organisms<\/a>, etc, for cleaning up yeast previously, but despite that I’ve yet to give a detailed example of how I go about cleaning up a contaminated yeast sample.<\/p>\n

Provenance has smiled down on me, in the form of an infected attempted bottle culture of a mixed sacch<\/i>\u00a0and brett<\/i>\u00a0fermented saison from The Bruery<\/a>, provided to me by a local home brewer. The contamination was not a “good” one – i.e. not a lactic acid bacteria contamination – but rather one that produced a rather putrid sulphur\/brimstone aroma.<\/p>\n

So how do we fix that…and how can we easily get pure strains of the brett<\/i> and sacc<\/i>\u00a0strains used in the beer?<\/p>\n

In this, the first part of a 2-part post (part 2 can be found here<\/a>), I will go through a basic procedure to enrich the Saccharomyces<\/i>\u00a0and Brettanomyces<\/i>\u00a0from the infected culture using a selective\/differential media and culture conditions to enable the growth of the desired yeast species while inhibiting the growth of the undesired bacteria and yeast. In part 2, hopefully posted later this week, I’ll go through a final clean-up procedure to ensure the resulting cultures are, in fact, clean of the contaminating yeast and bacteria.<\/p>\n

As always, details are below the fold…
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Quick Note:<\/h3>\n
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Unlike most of my posts and videos on “yeast ranching” type activities, I am not showing you how to do this in a home lab, and instead have done all of these procedures in my “real” microbiology laboratory. However, there is no reason why you couldn’t do this in your home lab, assuming you have some basic equipment.<\/p>\n<\/div>\n

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What You Need:<\/h3>\n<\/div>\n
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    \n
  1. An infected yeast culture<\/li>\n
  2. Sterile 1.040 wort, or another appropriate yeast medium<\/li>\n
  3. PenStrep (100X solution of penicillin and streptomycin)<\/li>\n
  4. Sterile culture tubes<\/li>\n
  5. A way to accurately measure small volumes (e.g. micropipette<\/a>)<\/li>\n
  6. Microscope with a minimum 600x magnification (optional, but strongly recommended)<\/li>\n
  7. Cycloheximide (10 ug\/ml, optional, but makes isolating brett<\/i>\u00a0from a mixed culture much easier)<\/li>\n
  8. Wort-agar plates<\/a> (or other compatable media, for step 2, covered in the next post).<\/li>\n
  9. A suitable work area<\/a> and the equipment required<\/a> for aseptic techniques<\/a>.<\/li>\n<\/ol>\n
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    Notes:<\/i><\/p>\n