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==General Information==
The method of fermenting wort with only ''Brettanomyces'' was pioneered by Tomme Arthur from Pizza Port/Lost Abbey, and Peter Bouckaert from New Belgium in 2004 with their 100% ''Brettanomyces'' fermentented ''Mo' Bretta'', and Vinnie Cilurzo of Russian River with Sanctification later that same year <ref>[http://www.amazon.com/American-Sour-Beer-Innovative-Fermentations-ebook/dp/B00LV8IRRI/ref=dp_kinw_strp_1 American Sour Beers. Michael Tonsmeire. July 2014. Pg 189.]</ref>. Avery Brewing Co. and Jeff O'Neal from Ithica Beer Co. also produced early 100% ''Brettanomyces'' beers <ref>[https://youtu.be/IGzoh4brILA?t=20m59s Yakobson, Chad. Interview on Craft Commander. 12/20/2016. Retrieved 12/20/2016.] (~21 mins in)</ref>. This method was further popularized by Chad Yakobson's ''Brettanomyces'' Dissertation on the [http://web.archive.org/web/20240519121257/http://www.brettanomycesproject.com/dissertation/ Brettanomyces Project blog], and by his brewery, [[Crooked Stave Artisan Beer Project]]. While primary fermentation with ''Brettanomyces'' is a complex subject due to the wide range of characteristics of different species and strains of ''Brettanomyces'', it is believed that beer that is fermented with ''Brettanomyces'' in primary usually produces a surprisingly clean, lightly fruity beer (see Chapter 8 in ''American Sour Beers'' by Michael Tonsmeire for a full description of 100% ''Brettanomyces'' fermented beers). However, much of this belief was partly based on the misclassification of what is now referred to as "''Saccharomyces'' Trois". The issue of characterizing 100% ''Brettanomyces'' fermentations is further complicated by the fact that some sources of ''Brettanomyces'' also contain ''Saccharomyces'' or other unadvertised microbes. Furthermore, most ''Brettanomyces'' strains cannot fully ferment wort due to not being able to utilize maltose (see the [[Brettanomyces#Carbohydrate_Metabolism_and_Fermentation_Temperature|''Brettanomyces'']] wiki page and [http://web.archive.org/web/20240623083404/http://brettanomycesproject.com/dissertation/pure-culture-fermentation/impact-of-pitching-rate/ Chad Yakobson's Dissertation]).
Typical characteristics of ''Brettanomyces'' primary fermentations (these are generalizations, and may not be true for every strain):
==Brewing Techniques==
===Obtaining a clean culture and true attenuation ability===
Please note that some of the ''[[Brettanomyces]]'' cultures products sold are by certain labs have been reportedly contaminated with other microbes such as ''[[Saccharomyces]]'' <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1295691083792436 MTF discussion on 2016-04-30]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1309024112459133/ MTF Discussion, 2016-05-19]</ref><ref>[http://babblebelt.com/newboard/thread.html?tid=1108752780&th=1281111541 Chad Yakobson. The Burgundian Babble Belt Homebrew forum. 08/12/2010.]</ref>. Generally, ''Brettanomyces'' ferments slow and a fermentation could take considerably longer to ferment out compared to a fermentation containing ''Saccharomyces'' (some specific strains of ''Brettanomyces'' are an exception to thisand may fully ferment wort in the same or similar timeframe as brewers yeast). Many strains of ''Brettanomyces'' have a somewhat limited [[Brettanomyces#Brettanomyces_Metabolism|metabolism]] and the apparent attenuation can be quite a bit lower compared to what a comparable ''Saccharomyces'' fermentation would showcase. Additionally, many strains of ''Brettanomyces'', especially many strains of ''B. anomalus'', cannot efficiently ferment maltose in brewing conditions, and therefore are not good candidates for 100% ''Brettanomyces'' beers (see [[Brettanomyces#Carbohydrate_Metabolism_and_Fermentation_Temperature|''Brettanomyces'' carbohydrate metabolism]] for details). If a ''Brettanomyces'' culture fully ferments out a beer in less than a month, then it may have a ''Saccharomyces'' contamination, however , there are exceptions to this (see [[100%25_Brettanomyces_Fermentation#Fermentation_Characteristics_of_Individual_Species_and_Strains|Fermentation Characteristics below]]). When using a yeast lab ''Brettanomyces'' product for 100% fermentation, it is advisable to contact the yeast lab regarding the ability of that strain(s) ability to fully ferment wort unless specifically noted on their product specification sheet/website.
===Starter Information===
===Fermentation Characteristics of Individual Species and Strains===
[https://link.springer.com/article/10.1007/s00217-022-04195-5 Cioch‑Skoneczny et al. (2023)] fermented a pale ale wort with and without grape must, pulp, and marc (pomice) using a single strain of ''B. bruxellensis'' (US-05 was used as a control). They found that the ''B. bruxellensis'' fermentations had a fermentation rate similar to US-05, although it took a bit longer to reach the same terminal gravity (while US-05 was finished fermenting after 9 days, the ''B. bruxellensis'' stalled after about day 6, and then started fermenting again at day 9 until reaching a similar final gravity around day 13). The ''B. bruxellensis'' was generally able to begin fermentation faster in the wine must/pulp/marc additions to wort. The ''B. bruxellensis'' consumed more FAN and was able to reduce malic acid, but it was less efficient at fermenting maltose than the US-05. This strain of ''B. bruxellensis'' did not express hyper-attenuation in these "100% Brett" fermentations <ref>[https://link.springer.com/article/10.1007/s00217-022-04195-5 Cioch-Skoneczny, M., Sral, A., Cempa, A. et al. Use of red grape pulp, marc and must in the production of beer. Eur Food Res Technol (2023). https://doi.org/10.1007/s00217-022-04195-5.]</ref>.
Not all species of ''Brettanomyces'' are effective at efficiently attenuating wort on their own. Additionally, some strains and species may produce better results flavor-wise than others.
* Not all strains can ferment maltose, which is almost 50% of the sugar composition of wort. These strains should be avoided for 100% ''Brettanomyes'' fermentations. See [[Brettanomyces#Carbohydrate_Metabolism|''Brettanomyces'' carbohydrate metabolism]] for more details.
* [http://web.archive.org/web/20240623083404/http://brettanomycesproject.com/dissertation/pure-culture-fermentation/impact-of-pitching-rate/ Chad Yakobson's thesis] showed that WLP645, WLP650, WLP653, WY5112, WY5526, and WY5151 were not able to attenuate wort more than 50% within 35 days (these were pure cultures). BSI Drie was the only strain tested that was able to attenuate wort at levels similar to brewers yeast. All strains that he tested were able to utilize maltose, however some less efficiently than others. More time may or may not have resulted in further attenuation. Contamination with another yeast is one explanation for why brewers are able ot use these cultures from labs to fully attenuate wort (Yakobson used purified isolates for this research).
* [https://www.facebook.com/groups/MilkTheFunk/permalink/1935201276508077/ Nick Mader of Fremont Brewing (2017 Master Brewers Conference Presentation)] observed that 100% BSI Drei fermentation resulted in around 77% attenuation (3.17°P final gravity), while co-fermentation with different pitch rates of a saison yeast resulted in around ~90% attenuation (~1.5°P final gravity). The esters were generally lower than when cofermented with the saison yeast, but ethyl decanoate (apple, brandy) was considerably higher with the 100% fermentation with BSI Drei. 4-ethyl phenol concentrations with 100% Drei were around the same as when cofermented with the saison yeast. See also [[Brettanomyces_and_Saccharomyces_Co-fermentation#Review_of_Scientific_Analysis|cofermentation with ''Saccharomyces'']].
A study <ref name="Tyrawa_2017">[https://www.facebook.com/groups/MilkTheFunk/permalink/1285391951489016/ "Funky can be Great: Brettanomyces bruxellensis Beer Fermentations" (poster for study). Caroline Tyrawa, Richard Preiss, and George van der Merwe. 2017.] </ref> conducted by Caroline Tyrawa and Richard Preiss measured, among other things, the 4-ethyl guaiacol in 100% ''Brettanomyces bruxellensis''. It shows significant levels of 4-ethyl guaiacol in wort fermented by various strains of the before-mentioned yeast. Tyrawa also showed that there are higher levels of esters in 100% ''Brettanomyces'' fermentations compared to when ''Brettanomyces'' is co-fermented with ''S. cerevisiae'' (see [[Brettanomyces_and_Saccharomyces_Co-fermentation#Review_of_Scientific_Analysis_2|''Brettanomyces'' and ''Saccharomyces'' Co-fermentation]]. A somewhat speculative conclusion of this might be that the high ester levels of 100% ''Brettanomyces'' fermented beers might mask the "funky" flavor characteristics of phenols (4-ethylguaiacol, 4-ethylphenol, etc). As esters tend to be chemically unstable (ref?) the fruity character of a ''Brettanomyces'' beer will fade over time allowing the funk a more prominent role. This is also supported by a study that looked at 4-ethylphenol and 4-ethylguaiacol levels in one strain of ''B. bruxellensis'' when fermented alone and when co-fermented with a wine strain (EC1118); they found that there were about 20% more phenols in the 100% ''B. bruxellensis'' fermentation than there were when the ''B. bruxellensis'' was co-fermented with EC1118 (this might have been because the wine strain uesd, EC1118, can metabolize hydrocinnamic precursors differently and reduce the 4-vinyl levels <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1770814702946736/ Richard Preiss. Statements about the Kosel et al. study. Milk The Funk Facebook gruop. 07/26/2017.]</ref>) <ref>[https://academic.oup.com/femsyr/article-abstract/17/4/fox018/3867021/The-influence-of-Dekkera-bruxellensis-on-the?redirectedFrom=fulltext The influence of Dekkera bruxellensis on the transcriptome of Saccharomyces cerevisiae and on the aromatic profile of synthetic wine must. Janez Kose, Neža Čade, Dorit Schulle, Laura Carret, Ricardo Franco-Duarte Peter Raspor. 2017.]</ref>, however, Tyrawa's data looked at phenol levels over time and found that initially phenol levels were higher in 100% ''Brettanomyces'' fermentations compared to co-pitched with ''S. cerevisiae'' but over time the phenol levels in the co-pitch were slightly higher and phenol levels in general fluctuated quite a bit over the entire 21 day trial <ref name="Tyrawa_Masters">[https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14757 Demystifying Brettanomyces bruxellensis: Fermentation kinetics, flavour compound production, and nutrient requirements during wort fermentation. University of Guelph, Masters Thesis. Department of Molecular and Cellular Biology. 2020.]</ref>.
[https://ir.library.oregonstate.edu/downloads/gh93h631p Riley Humbert's Bachelors thesis] reported that after a 30-35 day primary versus secondary fermentation with different strains of ''B. bruxellensis'', the primary fermentations tended to produce a wider spread of phenols based on strain but overall produced less phenols than when the same strains were fermented in secondary after a primary fermentation with London Ale III <ref>[https://ir.library.oregonstate.edu/downloads/gh93h631p Riley Humbert for the degree of Honors Baccalaureate of Science in Chemical Engineering presented on May 21, 2021. Title: Performance of Brettanomyces Yeast Strains in Primary and Secondary Beer Fermentations.]</ref>.
Thomas Hübbe's masters thesis also supports the hypothesis that ''Brettanomyces'' produces more esters other than ethyl acetate when it is not co-fermented with ''S. cerevisiae'', specifically because it has better growth without competition from ''S. cerevisiae''. Although below threshold, the esters ethyl caprylate, ethyl caprate, ethyl dodecanoate, and ethyl tetradecanoate were significantly lower when ''Brettanomyces'' was co-fermented with ''S. cerevisiae'' and ''Lactobacillus'' than when it was fermented with only ''Lactobacillus''. Ethyl acetate (still under threshold levels) was higher when ''Brettanomyces'' was fermented with ''Lactobacillus'' but without ''S. cerevisiae'', and significantly higher when it was fermented with both ''Lactobacillus'' and ''S. cerevisiae'' <ref name="Hubbe" />. This seems to support the idea that, with the exception of the ester ethyl acetate, 100% Brettanomyces fermentations are not necessarily less phenolic, but that they are more fruity probably due to higher growth without competition from ''S. cerevisiae'' (although phenols were not measured in Hübbe's study) <ref>[https://www.facebook.com/groups/MilkTheFunk/1407620505932826/?comment_id=1407723619255848&comment_tracking=%7B%22tn%22%3A%22R8%22%7D Comments by Richard Preiss regarding Thomas Hübbe's masters thesis. 09/15/2016.]</ref>.