Changes

Sulfite and SO₂ inhibits the growth of ''Brettanomyces'', and is often used in the wine industry to prevent the growth of ''Brettanomyces'' (although ''Brettanomyces'' is usually seen is a contaminant in wine, some wineries have identified small amounts of flavors from ''Brettanomyces'' as being beneficial to certain wine styles, and is said to increase the complexity and impart an aged character in young wines <ref name="smith_divol_2016"></ref>) <ref>[http://onlinelibrary.wiley.com/doi/10.1111/j.1745-4549.2012.00702.x/abstract Removal of Brettanomyces Bruxellensis from Red Wine Using Membrane Filtration. Umiker, Descenzo, Lee, and Edwards. 04/24/2012.]</ref>. However, it has been shown that wine strains of ''B. bruxellensis'' could survive dosages of up to 1 mg/L of molecular SO₂, and the very high dosage of 2.1 mg/L was needed to kill ''Brettanomyces'' in wine <ref name="Agnolucci_2017" />. This dosage of molecular SO₂ requires a total amount of SO₂ that is beyond legal limits (350 mg/l <ref>[https://grapesandwine.cals.cornell.edu/sites/grapesandwine.cals.cornell.edu/files/shared/documents/Research-Focus-2011-3.pdf Sulphur Dioxide Content of Wines: the Role of Winemaking and Carbonyl Compounds. Nick Jackowetz, Erhu Li, and Ramón Mira de Orduña. 2011.]</ref>; see this [https://grapesandwine.cals.cornell.edu/newsletters/appellation-cornell/2012-newsletters/issue-12/article-contains-sulfites/ Cornell University] blog post that explains the difference between ''free'' and ''molecular'' SO₂) and has negative effects on wine. One study found that out of 145 strains of ''B. bruxellensis'', 107 of which were wine strains with the rest being from beer, tequila, kombucha, etc., 36% of them were either tolerant (lagged growth, but achieved full growth eventually) or resistant (no lagged growth, and achieved full growth) to 0.6 mg/L of molecular SO₂. 46 of the 52 resistant/tolerant strains were wine strains, thus demonstrating that wine strains of ''B. bruxellensis'' are generally more tolerant of SO₂ than strains of ''B. bruxellensis'' that are found in other types of beverages. It is thought has been demonstrated that the wine strains have adapted to the conditions of winemakers adding SO₂ to wine <ref name="Bartel_2021">[https://academic.oup.com/femsyr/advance-article-abstract/doi/10.1093/femsyr/foab036/6293842 Caroline Bartel, Michael Roach, Cristobal Onetto, Chris Curtin, Cristian Varela, Anthony Borneman, Adaptive evolution of sulfite tolerance in Brettanomyces bruxellensis, FEMS Yeast Research, 2021;, foab036, https://doi.org/10.1093/femsyr/foab036.]</ref><ref>[https://www.frontiersin.org/articles/10.3389/fmicb.2018.01260/full Molecular Diagnosis of Brettanomyces bruxellensis’ Sulfur Dioxide Sensitivity Through Genotype Specific Method. Avramova M, Vallet-Courbin A, Maupeu J, Masneuf-Pomarède I, Albertin W. 2018. DOI: 10.3389/fmicb.2018.01260.]</ref>. There is also variability between wine strains in their ability to tolerate SO₂ <ref>[https://www.sciencedirect.com/science/article/abs/pii/S2212429221000250 Jessica Lleixà, Maria Martínez-Safont, Isabelle Masneuf-Pomarede, Maura Magani, Warren Albertin, Albert Mas, Maria C. Portillo. Genetic and phenotypic diversity of Brettanomyces bruxellensis isolates from ageing wines. Food Bioscience. Volume 40. 2021. ISSN 2212-4292. https://doi.org/10.1016/j.fbio.2021.100900.]</ref>. For example, ''Brettanomyces'' strains isolated from sweet wine tend to be more tolerant of sulfur dioxide than strains isolated from dry wine <ref>[https://www.sciencedirect.com/science/article/pii/S0740002018303988 Sulfur dioxide response of Brettanomyces bruxellensis strains isolated from Greek wine. Maria Dimopoulou, Magdalini Hatzikamari, Isabelle Masneuf-Pomarede, Warren Albertin. 2018. DOI: https://doi.org/10.1016/j.fm.2018.10.013.]</ref>. In addition, it has been proposed that SO₂ and other currently unidentified environmental stress factors can induce a so-called "viable but nonculturable" (VBNC) state in ''Brettanomyces'', which means that ''Brettanomyces'' cells in this state cannot grow or be cultured on traditional media but can remain viable and create a low amount of phenol character (see [[Quality_Assurance#VBNC_In_Yeast|VBNC in Yeast]]) <ref>[https://www.sciencedirect.com/science/article/abs/pii/S0740002020302069 Survival and metabolism of hydroxycinnamic acids by Dekkera bruxellensis in monovarietal wines. Adriana Nunes de Lima, Rui Magalhães, Francisco Manuel Campos, José António Couto. 2020. DOI: https://doi.org/10.1016/j.fm.2020.103617.]</ref>. Some strains of ''Candida pyralidae'', ''Wickerhamomyces anomalus'', ''Kluyveromyces wickeramii'', ''Torulaspora delbrueckii'' and ''Pichia membranifaciens'' have been found to produce toxin that inhibits ''Brettanomyces'', and these toxins have been proposed as an alternative to SO₂ as a way to kill ''Brettanomyces'' (killer wine strains of ''Saccharomyces cerevisiae'' do not kill ''Brettanomyces''; see [[Saccharomyces#Killer_Wine_Yeast|Killer Wine Yeast]] for more information). [http://www.laboratoriosenosan.com/en/effectiveness-of-kaolin-silver-complex/ Kaolin silver complex (KAgC)] has been found to inhibit ''Brettanomyces'' and acetic acid bacteria in wine when used in legal dosages, and has been proposed as a replacement for SO₂ or to minimize the use of SO₂ <ref>[https://www.ncbi.nlm.nih.gov/pubmed/29666535?dopt=Abstract Effect of kaolin silver complex on the control of populations of Brettanomyces and acetic acid bacteria in wine. Izquierdo-Cañas PM, López-Martín R, García-Romero E, González-Arenzana L, Mínguez-Sanz S, Chatonnet P, Palacios-García A, Puig-Pujol A. 2018. DOI: 10.1007/s13197-018-3097-y.]</ref>. Other proposed replacements for SO₂ as a way to inhibit ''Brettanomyces'' in wine include [https://en.wikipedia.org/wiki/Pascalization high pressure processing] and [https://www.sciencedirect.com/science/article/abs/pii/S0255270106001929 pulsed electric fields] <ref>[https://www.sciencedirect.com/science/article/pii/S1466856418302972 SO2, high pressure processing and pulsed electric field treatments of red wine: Effect on sensory, Brettanomyces inactivation and other quality parameters during one year storage. Sanelle Van Wyk, Mohammed M. Farid, Filipa V.M. Silva. 2018. DOI: https://doi.org/10.1016/j.ifset.2018.06.016.]</ref><ref>[https://www.sciencedirect.com/science/article/pii/S1466856418307409 Pulsed electric field treatment of red wine: Inactivation of Brettanomyces and potential hazard caused by metal ion dissolution. Sanellevan Wyk, Filipa V.M. Silva, Mohammed M.Farid. 2018. DOI: https://doi.org/10.1016/j.ifset.2018.11.001.]</ref>.

A study by Cibrario et al. (2019) looked at the genome of ''B. bruxellensis'' strains in bottles of wine going back as far as the year 1909 revealed that the SO₂ tolerant triploid strains only started appearing after the year 1990, which corresponds to when the wine industry started using SO₂ in most wine production (although it can also mean that the triploid strains are not as good at surviving in bottles of wine long-term compared to the diploid strains that have been isolated from much older bottles of wine; this will be determined to be the case or not in the future as bottles of wine from the 1990s continue to age). They also identified dozens of examples of wineries throughout France and Italy where the same strain of ''B. bruxellensis'' was found in multiple vintages of bottles of wine going back many decades, indicating that individual ''B. bruxellensis'' strains become long-term residents in wineries. Some identical strains have been found in different regions and even different continents, indicating that some strains have traveled not just due to traditional vectors such as insects or birds, but also probably due to human transportation such as wine bottle imports/exports or exchanges between industrial processes. This also indicates that while ''B. bruxellensis'' becomes rather sedentary and a constant resident in wineries, it can also adapt to the different winemaking conditions in different regions once it's been transported (different grapes, different climates, different fermentation temperatures, etc.), including adapting to improved modern hygienic practices such as higher SO₂ treatment. Overall, the results from this study suggest that ''Brettanomyces'' is able to adapt to living alongside certain human industries and has done so for at least a couple of centuries <ref name="Cibrario_2019">[https://www.biorxiv.org/content/10.1101/763441v1 Brettanomyces bruxellensis wine isolates show high geographical dispersal and long remanence in cellars. Alice Cibrario, Marta Avramova, Maria Dimopoulou, Maura Magani, Cécile Miot-Sertier, Albert Mas, Maria C. Portillo, Patricia Ballestra, View ORCID ProfileWarren Albertin, Isabelle Masneuf-Pomarede, Marguerite Dols-Lafargue. 2019. DOI: https://doi.org/10.1101/763441.]</ref>. The genetic differences between the fermentation substrates (beer, wine, etc.) were lower but still significant, and this was explained by the frequent cross-over of equipment such as wine barrels being used for beer fermentation. When comparing the geographic differences, they found geography contributed only 5% of genetic differences, while geography explained more than 50% of genetic differences in non-wine strains, suggesting that beer, kombucha, and tequila strains are more localized genetically than wine strains and that humans probably helped the wine strains travel across the globe. They also found that although one study reported spore-forming versions of ''B. bruxellensis'' (referred to as ''Dekkera bruxellensis''), the genetic makeup of the analyzed strains determined their ability to sporulate to be non-existent or rare (only one study that we know of by [https://link.springer.com/article/10.1007%2FBF02539015 Walt and Kerken in 1960] has reported sporulation in ''Brettanomyces'' only on specific agar types with vitamins added, indicating that sporulation in ''Brettanomyces'' is extremely rare) <ref name="Avramova_2018" />. See also [https://www.facebook.com/groups/MilkTheFunk/permalink/2022801681081369/ Richard Preiss's discussion of this study on MTF]. A study by [https://academic.oup.com/femsyr/advance-article-abstract/doi/10.1093/femsyr/foab036/6293842 Bartel et al. (2021)] used laboratory adaptive evolution methods to demonstrate that some strains of ''B. bruxellensis'' strains did in fact adapt to SO₂ usage in wineries <ref name="Bartel_2021" />.