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''Brettanomyces'', also known as brett or bretta, is a yeast that was originally thought of as a spoilage yeast. The genus name ''Dekkera'' is used interchangeably with Brettanomyces, as it describes the teleomorph or spore forming form of the yeast <ref>[http://en.wikipedia.org/wiki/Brettanomyces Wikipedia. Brettanomyces. Retrieved 2/24/2015.]</ref>. Known for it's barnyard, fecal, horsey, metallic or Band-Aid flavors, brett was unwelcome in most breweries. However, in some styles like Saison and Lambic these flavors add a layer of complexity to the beer. See [[Lactobacillus]], [[Pediococcus]], [[Saccharomyces]], and [[Mixed Cultures]] charts for other commercially available cultures.

''Brettanomyces'' strains may possess both alpha and beta glucosidases. These enzymes allow ''Brettanomyces'' strains to break down longer chain carbohydrate molecules and to liberate glycosidically bound sugars which are unfermentable to ''Saccharomyces'' yeasts.

Glycosides are sugar molecules connected to other organic compounds such as acids, alcohols, and aldehydes which are flavor and aroma inactive due to the sugar molecule attached. By cleaving off the sugar molecule through glucosidase activity, ''Brettanomyces'' species can liberate these compounds (called aglycones) into their aroma-active and flavor-active states, or states that may become flavor and aroma active through further modification<ref>Daenen et al., 2008. Evaluation of the glycoside hydrolase activity of a Brettanomyces strain on glycosides from sour cherry (Prunus cerasus L.) used in the production of special fruit beers. FEMS Yeast Res. 8, 1103-1114.</ref>. Therefore ''Brettanomyces'' strains are able to produce novel flavors and aromas from hops, fruits, and fruit pits that ''Saccharomyces'' yeasts cannot produce. In addition, the liberated aroma and flavor active compounds may be further processed by ''Brettanomyces'' through ester production or destruction pathways.

Brettanomyces is capable of forming several ethyl esters (derived from ethanol and fatty acids). Among these are ethyl acetate, ethyl lactate and phenethyl acetate, along with the hydrolysis of isoamyl acetate. During non-mixed fermentations where lactic acid and acetic acid are minimal to none, these esters are produced in smaller quantities <ref>[http://www.brettanomycesproject.com/dissertation/introduction/ Yakobson, Chad]. Pure Culture Fermentation Characteristics of Brettanomyces Yeast Species and Their Use in the Brewing Industry. Production of Secondary Metabolites. 2011.</ref>.

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Phenols such as 4-vinylphenol (4VP, barnyard, medicinal) and 4-vinylguaiacol (4-VG, clove) can be produced in beer by the decarboxylation of hydoxycinnamic acids, which are found in malt. While both ''Saccharomyces'' and ''Brettanomyces'' strains are capable of converting hydroxycinnamic acids to their vinyl derivatives, ''Brettanomyces'' is also able to reduce these vinyl derivatives to ethyl derivatives. These vinyl derivatives have similar tastes to the ethyl derivatives but have lower flavor thresholds.

fermentations with respect to time. Presentation at 2008 NHC. pg 12.</ref> <ref>[http://www.mbaa.com/districts/michigan/events/Documents/2011_01_14BrettanomycesBrewing.pdf Yakobson, Chad]. Brettanomyces in Brewing the horse the goat and the barnyard. 1/14/2011</ref>

In the presence of oxygen, ''Brettanomyces'' strains are capable of producing acetic acid. Depending on the brewer's palate and the degree of acetic production, this can be a desirable or undesirable trait. The degree of acetic acid production varies among different brett strains. Acetic acid produced by ''Brettanomyces'' may also be used in the synthesis of [[Secondary metabolites|acetate esters]] such as ethyl acetate. Brett has been shown to produce enough fatty acids in anaerobic fermentation to drop the pH to 4.0, which can also be esterified (see the ester table above) <ref name="yakobson1"></ref>. Many of these acids can have an unpleasant rancid odor and/or taste, which may be noticeable in young Brettanomyces beers before these acids are esterified.

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In cooperation with [http://www.funkfactorygeuzeria.com/2013/06/brett-strain-guide.html Funk Factory]

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Brettanomyces can be pitched into a beer at many points in the beer's fermentation life cycle. If used as the primary fermenter, the beer that is produced is often fruit forward and not very ''funky''. A large cell count will be needed (somewhere between an ale and lager pitching rate). See the [[100% Brettanomyces Fermentation]] page for more information. If pitched into a beer that has already been fermented by [[Saccharomyces]], a wider range of flavors including the ''funkier'' flavors can be produced (see the [[Brettanomyces#Brettanomyces_Metabolism|Brettanomyces Metabolism]] section above). A small cell count of Brettanomyces is plenty for creating these flavors, and normally a starter is not necessary. See the [[Mixed Fermentation]] and [[Funky Mixed Fermentations]] pages for more information on using Brett in secondary.

''Special thanks to Nick Impellitteri from [[The Yeast Bay]], and Shawn Bainbridge from Milk The Funk, for guidance on this section.''

It is worth noting that a "Malt Yeast Peptone Glucose" growth substrate has been shown to be a better substrate for growing an initial pitch of Brettanomyces. Specifically, when grown in wort, Brettanomyces will go through a 24 hour lag phase, a growth phase, another lag phase, and a second growth phase (all within 7-8 days). When grown in MYPG substrate, there is only a single growth phase and no lag phase, which has been reported by Yakobson to produce a larger cell count in the same amount of time <ref>[http://www.brettanomycesproject.com/2009/08/mypg-vs-wort-as-the-growth-substrate/ Yakobson, Chad. The Brettanomyces Project. MYPG Compared to Wort as a Growth Substrate. Retrieved 2/18/2015.]</ref>. Cells grown in MYPG also are better adapted to grow in wort <ref>[http://www.brettanomycesproject.com/dissertation/propagation-and-batch-culture-growth/propagation-discussion/ Yakobson, Chad. The Brettanomyces Project. Propagation and Batch Culture Discussion. Paragraph 5. Retrieved 2/18/2015.]</ref>. Practical instructions for making this substrate can be found on Jason Rodriguez's blog, "[http://sciencebrewer.com/2011/04/29/wild-yeast-project-mypg-culture-media/ Brew Science - Homebrew Blog]".

Store Brett at room temperature, and not refrigerated. 60-75°F/15.5-23.9°C should be acceptable (reference needed). Chad Yakobson noted that after storing Brett in a refrigerated environment, after 6 months the Brett would die. If Brett is stored cold, it will be very sluggish and slow to start fermentation. Making a starter is highly recommended if the Brett culture has been stored cold <ref>[http://youtu.be/AjVOzBtE27Y?t=43m Yakobson, Chad. Presentation at 2012 Music City Brew Off. At 43:00.]</ref>.

* [[100% Brettanomyces Fermentation]]

* [[Crooked Stave Artisan Beer Project]]

* [[Funky Mixed Fermentations]]

* [https://catalogue.ncyc.co.uk/catalogsearch/result/?q=brettanomyces National Collection of Yeast Cultures in the UK - Database on what compounds different species/strains can ferment.]

* [http://www.brettanomycesproject.com/ The Brettanomyces Project - Chad Yakobon's Brett research.]

* [http://www.themadfermentationist.com/p/commercial-cultures.html The Mad Fermentationist - Commercial Brettanomyces, Lactobacillus, and Pediococcus Descriptions]

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[[Category:Yeast]]