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added specific pitch rate for re-yeasting bottles
Commercial producers and MTFers have had success re-yeasting with their mixed culture, wine yeast, and champagne yeast. The specific yeast you choose is up to you, and we recommend that you try a couple different yeasts out to find the one you prefer. When re-yeasting at bottling, it is not recommended to add new highly attenuative yeast to make sure that the bottling yeast you add cannot ferment additional carbohydrates remaining in the beer <ref name='Sour Hour episode 6'/> (~41 minutes in). Re-yeasting with a yeast that beer has already seen should eliminate the possibility of continued attenuation as long as the beer is already at final gravity.
The yeast required for carbonation is very little. A good rule of thumb to use is to use 10% of the yeast that you would normally use for a primary fermentation(approximately 1 million cells per mL). For example, for dried yeast use ~2 grams of yeast for 5 gallons of beer <ref name="priming_calc">[http://jeffreycrane.blogspot.com/2015/06/blending-calculator-ph-abv-and.html Blending Calculator - pH, ABV and Carbonation. Jeff Crane. Blending Calculator - pH, ABV and Carbonation. Bikes, Beer, & Adventures Blog. June 12, 2015.]</ref>. Rehydrating the yeast is recommended. See [http://jeffreycrane.blogspot.com/2015/06/blending-calculator-ph-abv-and.html Jeff Crane's "Blending Calculator" (extension of Michael Tonsmeire's "Blending Calculator")] for a re-yeasting and priming calculator.
Many wine yeast strains are known to be "killer" yeast strains. In ''Saccharomyces'', killer strains produce toxins that kill sensitive strains. Neutral strains do not produce toxins, nor are they killed by them <ref>[https://books.google.com/books?hl=en&lr=&id=mvORN6OXHh4C&oi=fnd&pg=PA93&dq=Bussey,+H.+1981.+Physiology+of+killer+factor+in+yeast.+Adv.+Microb.+Physiol.+22:93-121&ots=jUY4T9NpgB&sig=aw-Y1um0KsDnGe6rRe5PTWIDYdI#v=onepage&q&f=false Advances in Microbial Physiology, Volume 22. Academic Press, Sep 15, 1981. Pg 94-95.]</ref>. Almost all ale and lager strains are sensitive to the toxins produced by killer strains <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1179271825434363/?comment_id=1179424538752425&offset=0&total_comments=5&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Bryan of Sui Generis Blog on MTF on Killer Factor for Saccharomyces. 11/16/2015.]</ref><ref>[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1973.tb03515.x/pdf Strains of Yeast Lethal to Brewery Yeasts. A.P. Maule and P.D. Thomas. 1972.]</ref>. In ''Saccharomyces'', four toxins have been identified: K1, K2, K28, and Klus, the first three of which can only kill other strains/species of ''Saccharomyces''. The Klus toxin has been found to kill yeast from other genra, such as ''Hanseniaspora spp.'', ''Kluyveromyces lactis'', ''Candida albicans'', ''Candida dubliniensis'', ''Candida kefir'' and ''Candida tropicalis'', and the K1, K2 and K28 killer strains of ''S. cerevisiae'' <ref name="Rodriguez">[http://aem.asm.org/content/77/5/1822.long A New Wine Saccharomyces cerevisiae Killer Toxin (Klus), Encoded by a Double-Stranded RNA Virus, with Broad Antifungal Activity Is Evolutionarily Related to a Chromosomal Host Gene. Nieves Rodríguez-Cousiño, Matilde Maqueda, Jesús Ambrona, Emiliano Zamora, Rosa Esteban and Manuel Ramírez. 2011]</ref>. However, none of the toxins have been found to kill ''Brettanomyces'' <ref>[http://www.scielo.org.za/scielo.php?pid=S2224-79042015000100010&script=sci_arttext&tlng=pt Non-Saccharomyces killer toxins: Possible biocontrol agents against Brettanomyces in wine? S. Afr. J. Enol. Vitic. vol.36 n.1 Stellenbosch. 2015.]</ref>. The K1 toxin is most active between a pH of 4.6 and 4.8, while K2 and Klus are active around a pH of 4.0 to 4.3 <ref name="Rodriguez"></ref>.