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Glycosides are flavorless compounds often found in plants/fruits that are composed of a molecule (often a flavor active compound) bound to a sugar molecule. The glycosidic bond can be broken, releasing the sugar molecule and the potentially flavor active compound. These bonds can be broken with exposure to acid, as well as specific enzymes which can be added synthetically or produced naturally by some microorganisms, including some strains of ''Brettanomyces'' <ref>[https://en.wikipedia.org/wiki/Glycoside "Glycoside." Wikipedia. Retrieved 06/27/2016.]</ref>. When the glycosidic bond is broken by an enzyme produced by a microorganism, it can be classified under the generic term as a [https://en.wikipedia.org/wiki/Biotransformation "biotransformation"] <ref>[http://www.sawislibrary.co.za/dbtextimages/17163.pdf Enzymes in Winemaking: Harnessing Natural Catalysts for Efficient Biotransformations - A Review. P. van Rensburg and I.S. Pretorius. 2000.]</ref>. The release of flavor molecules from glycosides is thought to contribute to the flavor development of aging wines, as well as kriek (cherry) lambic <ref name="Daenen2"></ref>. It is speculated that flavor compounds from hops can also be released from glycosides <ref name="Daenen1"></ref>.
==Glycosides and Beta-Glucosidase Activity==
Aglycones have been identified in many fruits and herbs such as grapes, apricots, peaches, yellow plums, quince, sour cherry, passion fruit, kiwi, papaya, pineapple, mango, lulo, raspberry, strawberry, and tea <ref name="Maicas">[http://www.ncbi.nlm.nih.gov/pubmed/15635463 "Hydrolysis of terpenyl glycosides in grape juice and other fruit juices: a review." Sergi Maicas, José Juan Mateo. May 2005.]</ref><ref name="Winterhalter"></ref>. They have been found in different parts of plants, including the green leafy parts, fruit, roots, rhizomes, petals, and seeds. Aglycones in plants are highly complex structures and very diverse, and their percentages can vary from crop to crop. In plants, these include alcohol type aglycones such as terpenols, terpenes, linalool oxides, as well as other flavor precursors including various alcohols, norisoprenoids, phenolic acids and probably volatile phenols such as vanillin <ref name="Maicas"></ref>. In fruits, there are mostly just 4 types of flavonol type aglycones: [https://en.wikipedia.org/wiki/Quercetin quercetin] (found in nearly all fruits), [https://en.wikipedia.org/wiki/Kaempferol kaempherol] (found in 80% of fruit), and less commonly [https://en.wikipedia.org/wiki/Quercetin quercetin] and [https://en.wikipedia.org/wiki/Isorhamnetin isorhamnetin] <ref>[https://books.google.com/books?id=vHqke7F4lWYC&pg=PA59&lpg=PA59&dq=aglycones+in+fruit&source=bl&ots=7Gb10SPZk7&sig=6gaZlwpVaHuteoiVP68zvt6HcpE&hl=en&sa=X&ved=0ahUKEwjk0qW9wp3NAhUCKZQKHfUzDrQQ6AEIKTAC#v=onepage&q=aglycones%20in%20fruit&f=false Fruit Phenolics. Jean-Jacques Macheix, Annie Fleuriet. CRC Press, Mar 20, 1990. Pgs 57-61.]</ref> (see [http://nutrition.ucdavis.edu/content/infosheets/fact-pro-flavonol.pdf this UC Davis PDF] for amounts in different fruit and potential health benefits as antioxidants). In many cases of fruit, the amount of aromatic aglycones that are bound up in glycosides outnumber the amount that are free in a ratio of 2:1 to 8:1 <ref name="Maicas"></ref>. Aglycones that are bound up in glycosides tend to be more water soluble and less reactive once unbound than the naturally free version. By providing enzymes that break the glycosidic bond, discarded parts of plants (peels, stems, skins, etc.) have been used to produce natural flavorings from the remaining and abundant glycosides <ref name="Winterhalter">[http://link.springer.com/chapter/10.1007%2FBFb0102063 "Glycoconjugated aroma compounds: Occurrence, role and biotechnological transformation." Peter Winterhalter, George K. Skouroumounis. 1997.]</ref>.
===Acidic Hydrolysis===
Aglycones can be released from glycosides via a low pH. Generally, this occurs at lower pH's and Daenen et al. (2007) attributed most of the breakdown of glycosides to beta-glucosidase enzymes <ref name="Daenen2" />, but different types of glycosides are more readily broken down at different pH's. For example, ocimenols (lemon, lime <ref>[http://www.thegoodscentscompany.com/data/rw1020581.html "Ocimenol". The Good Scents Company. Retrieved 06/26/2017.]</ref>) are formed from glycoside breakdown at a pH of 1, but terpenes such as linalool, nerol, and geraniol (commonly found in hops and other plant material) are formed at a pH of 3, and alpha-terpineol was formed at both pH values. The acidic breakdown of these glycosides were found to contribute to the flavor of wine during aging <ref name="Maicas"></ref>. Daenen et al. (2007) also found that acidic hydrolysis was responsible for the formation of alpha-ionol, beta-damascenone, linalool and alpha-terpineol and to a lesser extent benzyl alcohol <ref name="Daenen2" />.
In beer, it was found that the lower the pH of the beer the higher the amount of the ketone damascenone (floral, rose <ref>[https://en.wikipedia.org/wiki/Damascenone "Damascenone". Wikipedia. Retrieved 06/26/2017.]</ref>) and dimethyl trisulfide (sulfury cooked onion <ref>[http://www.thegoodscentscompany.com/data/rw1008101.html "Dimethyl trisulfide". The Good Scents Company. Retrieved 06/26/2017.]</ref>). In one study, at a pH of 3, beta-damascenone was reported to be ~27 ppb and dimethyl trisulfide was reported to be 650 ppt. At a pH of 4.2, they were 17 ppb and 300 ppt respectively. At a ph of 5, beta-damascenone was around 12 ppb and dimethyl trisulfide 50 ppt. This was believed to be due to the acidic hydrolysis of glycosides, and it was speculated that other glycosides could have a flavor impact on beers that contain fruit or herbs due to acidic hydrolysis of glycosides <ref>How Low pH Can Intensify ?-Damascenone and Dimethyl Trisulfide Production through Beer Aging. LAURENCE GIJS, FABIENNE CHEVANCE, VESNA JERKOVIC, AND SONIA COLLIN. 2002. DOI: 10.1021/jf020563p.</ref>.
* See also: [[Hops#Glycosides|Glycosides In Hops]].
===Beta-Glucosidase===
Aglycones can also be released chemically from glycosides by either exposure to acid (generally pH of 3 or lower, and different pH's giving different results on which glycosides are broken down; this breakdown of glycosides under low pH has been linked to the slow flavor development of aging wine <ref name="Maicas"></ref>), or by enzymes called beta-glucosidases. Enzymatic breakdown of glycosides has been described as producing a more "natural" flavor in wines versus acidic breakdown. Some fruits have been observed (mostly wine grapes) to have limited beta-glucosidase activity within themselves, however it has been observed as being unstable and having low activity at the low pH of wine and sour beer <ref name="Maicas"></ref>.
Beta-glycosidase enzymes can be added artificially, however there has been much interest in the natural capability of microorganisms to produce beta-glucosidases, particularly 1,4-β-glucosidase <ref name="Winterhalter"></ref>. Microorganisms that can break down glycosides by using beta-glucosidases can then access the resulting sugars for fermentation <ref name="Steensels">[http://www.sciencedirect.com/science/article/pii/S0168160515001865 Brettanomyces yeasts — From spoilage organisms to valuable contributors to industrial fermentations. Jan Steensels, Luk Daenen, Philippe Malcorps, Guy Derdelinckx, Hubert Verachtert, Kevin J. Verstrepen. International Journal of Food Microbiology Volume 206, 3 August 2015, Pages 24–38.]</ref>. There are two major categories of glucosidase activity: endogenous and exogenous. Endogenous enzymatic activity takes place inside of the cell, and exogenous enzymatic activity takes place outside of the cell. Bacteria and fungi that show endogenous glucosidase activity have been shown not to be effective in alcoholic fermentation due to not tolerating low pH (optimum pH of 5), glucose, and/or ethanol. Generally, the flavorless glycosides remain unaffected by yeast fermentation, leaving them unused as a potential source for flavor and aroma <ref name="Winterhalter"></ref>.
Different types of beta-glucosidase enzymes have different optimal pH and temperatures. For example, beta-glucosidase produced from ''A. niger'' is optimal at a pH of 4.5 and a temperature of 58°C (136°F), whereas the enzyme for ''Brettanomyces anomalus'' is optimal at a pH of 5.75 and a temperature of 37°C (98°F) (it was active to some extent between 15°-55°C). The beta-glucosidase enzyme ceases effectiveness below a pH of 4.5 for one strain of ''B anomalus'' studied <ref name="Vervoort"></ref>.
See also:* [http://www.cazy.org/Glycoside-Hydrolases.html Database of glycoside hydrolases.] ===Activity of ''Brettanomyces '' and ''Saccharomyces''=== [http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2007.03566.x/full Daenen et al. (2007)] screened the beta-glucosidase activity of several strains of ''Saccharomyces cerevisiae'', ''Saccharomyces pastorianus'', and several ''Brettanomyces'' species. None of the lager brewing strains showed beta-glucosidase activity. Out of 32 strains of ''S. cerevisiae'', only one strain (a wine strain called "U228") showed beta-glucosidase activity, however its activity was repressed in the presence of glucose. This indicates that most ''S. cerevisiae'' strains do not have the capability of producing beta-glucosidase, but it is possible that some very few strains can <ref name="Daenen1">[http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2007.03566.x/full Screening and evaluation of the glucoside hydrolase activity in Saccharomyces and Brettanomyces brewing yeasts. L. Daenen, D. Saison, F. Sterckx, F.R. Delvaux, H. Verachtert, G. Derdelinckx. 2007.]</ref>. Additionally, beta-glucosidase activity for ''S. cerevisiae'' can be inhibited by the pH levels found in wine and sour beer (optimal at pH 5) <ref name="Mansfield"></ref>. All strains of ''S. cerevisiae'' did release another enzyme called beta-glucanase, which led to varying degrees of breaking down some smaller glycosides found in hops (hop extract was tested, not whole hops) containing the aglycones methyl salicylate, 1-octen-3-ol, and cis-3-hexen-1-ol, but not linalool. None of the ''B. bruxellensis'' strains showed this activity, but the researchers only tested strain of ''B. custersianus'' and both of the ''B. anomala'' strains tested did show cell-associated (intracellular) beta-glucosidase activity. In particular, the ''B. custersianus'' strain was tested against glycosides from hops, in which case high amounts of the aglycones linalool (citrus, orange, lemon, floral <ref>[http://www.thegoodscentscompany.com/data/rw1007872.html "Linalool." The Good Scents Company. Retrieved 05/12/2016.]</ref>), methyl salicylate (minty, wintergreen <ref>[http://www.rsc.org/chemistryworld/2015/09/methyl-salicylate-oil-wintergreen-podcast "Methyl salicylate." Chemistry World. Retrieved 05/12/2016.]</ref>), 1-octen-3-ol (mushroom, earthy <ref>[http://www.thegoodscentscompany.com/data/rw1024051.html "1-octen-3-ol." The Good Scents Company. Retrieved 05/12/2016.]</ref>) and cis-3-hexen-1-ol (grassy, melon rind <ref>[http://www.thegoodscentscompany.com/data/rw1005932.html "(Z)-3-hexen-1-ol." The Good Scents Company. Retrieved 05/12/2016.]</ref>) were released from hop extracts <ref name="Daenen1"></ref>. The beta-glucosidase activity was elevated when co-fermenting ''B. custersianus'' with ''S. cerevisiae''. The authors also found dihydroedulan 1 and 2 (elderberry aroma) and theaspirane A and B (woody and campfire aromas), which are classified as norisoprenoids, were released from dry hopping <ref>[http://www.asbcnet.org/events/archives/Documents/2008WBCprogbook.pdf World Brewing Congress, 2008. Pg 80. Retrieved 05/13/2016.]</ref>. ''B. custersianus'' has been isolated from the later stages of lambic fermentation, and it is thought that its ability to produce beta-glucosidase, which gives it the ability to ferment cellobiose and cellotriose, is a possible adaptation from living in oak barrels <ref name="Daenen1"></ref>. Recent studies on hops have linked an increase in fruity thiols from hops (3-mercaptohexan-1-ol and 4-mercapto-4-methylpentan-2-one) being produced during fermentation from the production of beta-lyase enzyme, and this could also explain anecdotal reports of increased fruity aromas from exposing hops to fermentation (see [http://scottjanish.com/genetically-modified-gm-yeast-strains-unlocking-bound-hop-thiols-and-engineering-targeted-fermentation-characteristics/ this article by Scott Janish] on beta-lyase enzymes in GM and non-GM yeast strains). <ref>Private correspondence with Richard Preiss by Dan Pixley. 05/16/2016.</ref><ref>[https://beerandbrewing.com/VuhJRCUAAHMUNfil/article/hops-oils--aroma-uncharted-waters "Hops Oils & Aroma: Uncharted Waters," by Stan Hieronymus. Beer & Brewing. 03/16/2016. Retrieved 05/16/2016.]</ref>. [https://www.academia.edu/23874347/Properties_of_endogenous_%CE%B2_glucosidase_of_a_Saccharomyces_cerevisiae_strain_isolated_from_Sicilian_musts_and_wines Palmeri et al. (2002)] reported one wine strain out of 80 strains of ''S. cerevisiae'' found in Sicilian must that had high beta-glucosidase activity and is active during wine fermentation conditions <ref>[https://www.academia.edu/23874347/Properties_of_endogenous_%CE%B2_glucosidase_of_a_Saccharomyces_cerevisiae_strain_isolated_from_Sicilian_musts_and_wines Spagna, G., Barbagallo, R. N., Palmeri, R., Restuccia, C., & Giudici, P. (2002). Properties of endogenous β-glucosidase of a Saccharomycescerevisiae strain isolated from Sicilian musts and wines. Enzyme and Microbial Technology, 31(7), 1030–1035. https://doi.org/10.1016/S0141-0229(02)00233-8]</ref>. Another study by [http://onlinelibrary.wiley.com/doi/10.1002/jib.418/abstract Sharp et al.] found that both ale and lager yeasts exhibit a wide range of beta-glucosidase activity, but the results should be repeated using a different substrate because the substrate that was used could have been broken down by beta-glucanase enzyme instead of beta-glucosidase <ref name="Sharp_2017">[http://onlinelibrary.wiley.com/doi/10.1002/jib.418/abstract The effect of hopping regime, cultivar and β-glucosidase activity on monoterpene alcohol concentrations in wort and beer. Daniel C. Sharp, Jan Steensels, Thomas H. Shellhammer. 2017.]</ref>Additionally, Lallemand claims that three brewing strains that they offer produce beta-glucosidase enzymes that can promote hop biotransformation, but the details of this activity have not been published to our knowledge (BRY-97, New England, and Belle Saison) <ref>[http://masterbrewerspodcast.com/119-biotransformation Eric Abbot. Master Brewers Association podcast, episode 119. 02/04/2019.]</ref> (~8:50 min in). The same strain of ''B. custersianus'' was screened for beta-glucosidase activity and aglycone byproducts during the refermentation of sour cherries in beer (a very small amount of the byproducts were manufactured by the yeast ''de novo'', particularly linalool, alpha-terpineol, alpha-ionol, and a precursor that leads to beta-damascenone under low pH conditions). Different portions of the cherries were tested: whole cherries with stones (pits), cherry pulp without stones, cherry juice without stones or other solids from the fruit, and the stones alone. Benzaldehyde (almond, cherry stone flavor) was produced during fermentation in all cases, and reduced to benzyl alcohol (almond flavor) and benzyl acetate (fruity, jasmine flavor) by the end of fermentation. There were higher levels of these benzyl based compounds in the whole cherries and cherry stone alone samples, indicating that cherry stones make a big impact on the almond flavors found in cherry sour beers. Methyl salicylate, linalool, alpha-terpineol (pine), geraniol (rose, lime, floral) and alpha-ionol (floral, violet), eugenol (spicy, clove, medicinal) and isoeugenol (fine delicate clove) levels increased in all forms of cherries added except for stones alone, indicating that these aglycones are more present in the flesh and juice of the cherries <ref name="Daenen2"></ref>. Another study that performed whole genome sequencing on a strain of ''B. naardenensis'' found that it had two genes that could potentially allow this species to produce beta-glucosidase, but this was not confirmed in the study <ref>[https://www.mdpi.com/2076-2607/7/11/489 Assembly and Analysis of the Genome Sequence of the Yeast Brettanomyces naardenensis CBS 7540. Ievgeniia A. Tiukova, Huifeng Jiang, Jacques Dainat, Marc P. Hoeppner, Henrik Lantz, Jure Piskur, Mats Sandgren, Jens Nielsen, Zhenglong Gu, and Volkmar Passoth. 2019. DOI: https://doi.org/10.3390/microorganisms7110489.]</ref>. Many strains of ''B. bruxellensis'' have also been found to have varying degrees of intracellular (produced inside the cell only) or parietal (attached to the cell wall) beta-glucosidase activity. At least one mutant strain of ''B. bruxellensis'' found in wine (''D. bruxellensis'' BCRC920084 from the Bioresource Collection and Research Center, Hsin-Chu, Taiwan) has been reported to have high extracellular (excreted out of the cell) production of beta-glucosidase that was very efficient at breaking down a glycoside called "piceid" that released resveratrol, which has been marketed as a dietary supplement <ref>[https://www.ncbi.nlm.nih.gov/pubmed/29389552?dopt=Abstract Characterization of an extracellular β-glucosidase from Dekkera bruxellensis for resveratrol production. Kuo HP, Wang R, Huang CY, Lai JT, Lo YC, Huang ST. 2018.]</ref><ref>[https://en.wikipedia.org/wiki/Resveratrol Wikipedia. "Resveratrol" article. Retrieved 02/09/2018.]</ref>. ''Brettanomyces'' has more strains that can produce beta-glucosidase than other genera of yeast, and the strains generally also have a higher rate of beta-glucosidase activity than other genera of yeast <ref>[http://link.springer.com/article/10.1038/sj.jim.2900720 Quantification of glycosidase activities in selected yeasts and lactic acid bacteria. H McMahon, B W Zoecklein, K Fugelsang, Y Jasinski. 1999.]</ref><ref name="Mansfield"></ref>. Strains with higher beta-glucosidase activity have been isolated from lambic, suggesting that these strains may have an adapted ability to utilize sugar from glycosides <ref name="Vervoort">[http://onlinelibrary.wiley.com/wol1/doi/10.1111/jam.13200/abstract Characterization of the recombinant Brettanomyces anomalus β-glucosidase and its potential for bioflavoring. Yannick Vervoort, Beatriz Herrera-Malaver, Stijn Mertens, Victor Guadalupe Medina, Jorge Duitama, Lotte Michiels, Guy Derdelinckx, Karin Voordeckers, and Kevin J. Verstrepen. 2016.]</ref>. Some ''Brettanomyces'' strains may only be capable of beta-glucosidase activity, and not the other enzymes which are needed to break down disaccharide type glycosides. Additionally, cell death and autolysis can result in an increase in beta-glucosidase activity in solution due to the cell contents being released into solution <ref name="Mansfield"></ref>. Strains that can metabolize cellobiose tend to also have higher beta-glucosidase activity because they possess an extra gene for beta-glucosidase enzyme production <ref name="Crauwels1">[http://link.springer.com/article/10.1007/s00253-015-6769-9 Comparative phenomics and targeted use of genomics reveals variation in carbon and nitrogen assimilation among different Brettanomyces bruxellensis strains. S. Crauwels, A. Van Assche, R. de Jonge, A. R. Borneman, C. Verreth, P. Troels, G. De Samblanx, K. Marchal, Y. Van de Peer, K. A. Willems, K. J. Verstrepen, C. D. Curtin, B. Lievens. 2015]</ref>. Sensory analysis of beers with cherries or hops have shown that there is a significantly detectable difference between cherry beers that have been exposed to beta-glucosidase from one strain of ''B. anomalus'' versus not exposed to the enzyme, but no significant difference was found in beers hopped with pellets. The cherry beers exposed to the enzyme contained more and above odor threshold eugenol (clove, honey aroma), benzyl alcohol (sweet, flower), benzaldehyde (almond, cherry) than cherry beers that were not exposed to the enzyme. The cherry beers exposed to the enzyme were not only identified in a blind tasting but were also preferred to the cherry beers without exposure to the enzyme, indicating that beta-glucosidase activity in cherry beers provides a significant flavor difference. Other types of beta-glucosidase enzymes released different levels of different flavor compounds, indicating that the source (bacteria or yeast) of the enzyme make a significant difference in the flavors that are produced <ref name="Vervoort"></ref>. The effects of beta-glucosidase on hops may be limited even in ideal conditions using pure beta-glucosidase that is highly efficient in beer where beta-glucosidase activity by yeast is limited. Sharp et al. (2017) determined that hops contain such a small amount of glycosides that their release doesn't contribute much to hop flavor and aroma. While previous studies focused on hop extracts, they studied glycosides in whole leaf hops for the first time and found non-significant levels of hop-derived monoterpenes from glycosides even when using pure beta-glucosidase extracted from almonds. For example, linalool was increased by 16.5 μg/L when using the highest hopping rate, but this amount has little impact on the overall aroma and flavor of the beer. Terpineol, citronellol, nerol, and geraniol were also not increased in significant amounts, however 1-octanol (waxy, green, citrus, orange, aldehydic, fruity <ref>[http://www.thegoodscentscompany.com/data/rw1021071.html Octanol. The Good Scents Company. Retrieved 03/31/2017.]</ref>) was increased significantly <ref name="Sharp_2017" />. In 2020, whole genome sequencing and glycosidic activity were tested for 84 strains of ''Brettanomyces'' by [https://www.frontiersin.org/articles/10.3389/fmicb.2020.00637/full Colomer et al]. They found that the capability of ''Brettanomyces'' to break down glycosides is determined by possessing two genes: ''BbBGL1'' and ''BbBGL2''. The genes called ''BbBGL2'' have a major role in whether glycosides are broken down, while the role of ''BbBGL1'' is minimal. About half of the strains had some level of glycosidic activity, although the majority was low with a couple of strains that had high levels of glycosidic activity, thus these genes alone do not account for the wide variation in glycosidic activity levels in ''Brettanomyces'' (see [https://www.frontiersin.org/files/Articles/495404/fmicb-11-00637-HTML-r1/image_m/fmicb-11-00637-g007.jpg this figure] from the study which maps beta-glucosidase activity for the 84 strains that were sequenced) <ref>[https://www.frontiersin.org/articles/10.3389/fmicb.2020.00637/full Assessing Population Diversity of Brettanomyces Yeast Species and Identification of Strains for Brewing Applications. Marc Serra Colomer, Anna Chailyan, Ross T. Fennessy, Kim Friis Olsson, Lea Johnsen, Natalia Solodovnikova and Jochen Forster. 2020. DOI: https://doi.org/10.3389/fmicb.2020.00637.]</ref>. The beta-glucidase levels were also measured for 5 strains (4 strains of ''B. bruxellensis'' and 1 strain of ''B. anomalus'') that have the genetic make up to produce this enzyme; most of the enzyme was only produced within the cell (intracellular) for all of the strains tested, and only small amounts were produced outside of the cells except for one strain of ''B. anomalus''. The enzyme therefore wouldn't act on glycosides outside of the cell unless the cell ruptured. There was also a small amount of beta-glucosidase activity within the cell wall of one of the strains of ''B. anomalus''. They also fermented a dry hopped beer with these strains and found that the strains with the lowest beta-glucosidase activity had the lowest conversion of geraniol to β‐citronellol, and therefore there was no correlation between beta-glucosidase activity and hop biotransformation (although there was evidence of another unidentified type of biotransformation occurring with the hops (see [[Brettanomyces#Hop_Biotransformation|''Brettanomyces'' hop biotransformation]]) <ref>[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.610 Biotransformation of hop derived compounds by Brettanomyces yeast strains. Marc Serra Colomer, Birgitte Funch, Natalia Solodovnikova, Timothy John Hobley, Jochen Förster. 2020. DOI: https://doi.org/10.1002/jib.610.]</ref>. Wang et al. (2018) reported another type of glycosidic activity in one strain of ''B bruxellensis'' which is the conversion of the glycoside "mogroside V" into an artificial sweetener called siamenoside I. Other yeast and bacteria species were tested and did not find this particular glycosidic activity. [https://en.wikipedia.org/wiki/Mogroside Mogroside V] is found naturally in some fruit, specifically, an Asian fruit called [https://en.wikipedia.org/wiki/Siraitia_grosvenorii Lo Han Kuo (''Siraitia grosvenorii'')]. The artificial sweetener siamenoside is 563 times sweeter tasting than 5% sucrose. The specific enzyme responsible for this conversion that this strain of ''B. bruxellensis'' produced is called ''Db''Exg1 <ref>[https://www.sciencedirect.com/science/article/pii/S0308814618317473 Dekkera bruxellensis, a beer yeast that specifically bioconverts mogroside extracts into the intense natural sweetener siamenoside I. Reuben Wang, Yi-Chieh Chen, Yun-Ju Lai, Ting-Jang Lu, Shyue-Tsong Huang, Yi-Chen Lo. 2018. DOI: https://doi.org/10.1016/j.foodchem.2018.09.163.]</ref>. See also:* [[Hops#Glycosides|Glycosides in Hops]].* [http://scottjanish.com/genetically-modified-gm-yeast-strains-unlocking-bound-hop-thiols-and-engineering-targeted-fermentation-characteristics/ "Genetically Modified (GM) Yeast Strains: Unlocking Bound Hop Thiols and Engineering Targeted Fermentation Characteristics," by Scott Janish.] ===Activity of Other Yeasts===A strain of ''Candida glabrata'' was selected in a study for its high beta-glucosidase activity, its tolerance to ethanol, and its ability to utilize maltose, and was shown to produce novel flavor characteristics in beer fermentation, including a significant increase in geraniol <ref>[https://www.sciencedirect.com/science/article/abs/pii/S0308814622026887#f0020 Application of non-Saccharomyces yeasts with high β-glucosidase activity to enhance terpene-related floral flavor in craft beer. Xiaoyu Han, Qiuxing Qin, Chenyu Li, Xiaoxuan Zhao, Fangxu Song, Mengjiao An, Ying Chen, Xiuqin Wang, Weidong Huang, Jicheng Zhan, Yilin You. 2022.]</ref>. Strains of ''Meyerozyma guilliermondii'' and ''Hanseniaspora uvarum'' that were isolated from a spontaneous wine fermentation have also been found to have positive results when co-fermented with ''S. cerevisiae'' in wine. Specifically, compared to the control wines, there were higher levels of the terpenes: isopulegol, citronellol, geranylacetone, geraniol, trans-nerolidol, and nerol. This was associated with the high beta-glucosidase activity of these yeast strains <ref>[https://www.frontiersin.org/articles/10.3389/fmicb.2022.845837/full Indigenous Non-Saccharomyces Yeasts With β-Glucosidase Activity in Sequential Fermentation With Saccharomyces cerevisiae: A Strategy to Improve the Volatile Composition and Sensory Characteristics of Wines. Gao Pingping, Peng Shuai, Sam Faisal Eudes, Zhu Yatong, Liang Lihong, Li Min, Wang Jing. 2022.]</ref>. ===Activity of Lactic Acid Bacteria===(To do) http://www.icfsnmalaysia2017.org/ICFSN2017%20proceedings%20-%20pp%2054-60.pdf
===Cyanogenic Glycosides===
All plants contain at least tiny amounts of [https://en.wikipedia.org/wiki/Hydrogen_cyanide hydrogen cyanide] ('''HCN'''), however, some plants also release high amounts of HCN from a class of glycosides called "cyanogenic glycosides", also called "cyanoglycosides". [https://en.wikipedia.org/wiki/Amygdalin Amygdalin] and [https://en.wikipedia.org/wiki/Linamarin linamarin] are common examples of cyanogenic glycosides <ref name="Gleadow_2014"></ref>. Amygdalin is sometimes marketed as a cure for cancer by the health food industry, but this claim is not supported by clinical data, and digestion of too much amygdalin can be dangerous <ref>[https://www.quackwatch.org/01QuackeryRelatedTopics/Cancer/laetrile.html Wilson, Benjamin. "The Rise and Fall of Laetrile". Quackwatch.org website. 01/07/2017. retrieved 03/30/2017.]</ref><ref>[http://www.nejm.org/doi/pdf/10.1056/NEJM198201283060403 A Clinical Trial of Amygdalin (Laetrile) in the Treatment of Human Cancer. Charles G. Moertel, M.D., Thomas R. Fleming, Ph.D., Joseph Rubin, M.D., Larry K. Kvols, M.D., Gregory Sarna, M.D., Robert Koch, M.D., Violante E. Currie, M.D., Charles W. Young, M.D., Stephen E. Jones, M.D., and J. Paul Davignon, Ph.D. 1982. DOI: 10.1056/NEJM198201283060403.]</ref><ref>[https://www.infona.pl/resource/bwmeta1.element.springer-2c7e4ea1-3683-3bbd-9394-a98a551e7c63 Laetrile for cancer: a systematic review of the clinical evidence. Stefania Milazzo, Stephane Lejeune, Edzard Ernst. 2007. DOI: 10.1007/s00520-006-0168-9.]</ref><ref>[http://www.sciencedirect.com/science/article/pii/S0944711316000362 Amygdalin, quackery or cure? Roman A. Blahetaa, Karen Nelsonb, Axel Haferkampa, Eva Juengela. 2016.]</ref>. HCN is released from cyanogenic glycosides just like other types of glycosides: beta-glucosidase enzyme or exposure to low pH breaks the bond between a glucose molecule and an unstable compound called "cyanohydrin" (or "alpha-hydroxynnitrile"), which then disassociates into a ketone or benzaldehyde and an HCN molecule. In progresscyanogenic glycosides, this reaction is called "cyanogenesis". Cyanogenesis is stimulated by maceration, and by bacteria in the human gut <ref name="Speijers">[http://www.inchem.org/documents/jecfa/jecmono/v30je18.htm "Cyanogenic Glycosides", First Draft. Dr G. Speijers. National Institute of Public Health and Environmental Protection Laboratory for Toxicology, Bilthoven, The Netherlands. Retrieved 08/25/2016.]</ref>. Although the optimum pH of cyanogenesis (at least for amygdalin)is 5.0 - 5.8, cyongenesis can occur at a wide range of pH values, and can occur in the presence of acid <ref>[http://www.sciencedirect.com/science/article/pii/S0308814601003132 Total cyanide determination of plants and foods using the picrate and acid hydrolysis methods. M Rezaul Haque, J Howard Bradbury. 2002.]</ref>. If seeds containing cyanogenic glycosides are ground up, the coarseness to which they are ground effects how quickly cyanogenesis occurs. Finely ground seeds extract HCN within an hour, where as coarsely ground seeds extract within 24 hours <ref name="tuncel">[http://www.sciencedirect.com/science/article/pii/030881469599841M The effects of grinding, soaking and cooking on the degradation of amygdalin of bitter apricot seeds. G Tunçel, M.J.R Nout, L Brimer. 1995.]</ref>. HCN boils at a relatively low temperature (25.6°C / 78.1°F) <ref name="Gleadow_2014"></ref>. In some cases, soaking, cooking, and/or sometimes fermenting foods with certain bacteria or yeast (this has not been fully documented with ''Saccharomyces'' or ''Brettanomyces'') that contain cyanogenic glycosides allows the HCN to be released, and then subsequent cooking afterwards will boil off the cyanide <ref>[http://www.sciencedirect.com/science/article/pii/016816059400115M International Journal of Food Microbiology. M.J.R. Nout, G. Tunçe, L. Brimer. 1995.]</ref><ref name="Chaouali"></ref>.
{| class="wikitable sortable"
|-
! Plant !! mg HCN/kg or mg/liter <nowiki>*</nowiki> || Prominent Glycoside
|-
| Cereal grains and their products || 0.001-0.45 <ref name="who">[http://www.who.int/ipcs/publications/cicad/en/cicad61.pdf Concise International Chemical Assessment Document 61. HYDROGEN CYANIDE AND CYANIDES: HUMAN HEALTH ASPECTS. World Health Organization. 2004. Pg 13. Retrieved 08/29/2016.]</ref> ||
|-
| Soybean hulls || 1.24 <ref name="who"></ref> || Linmarin <ref name="soybean"></ref>
|-
| Home-made cherry juice from pitted fruits || 5.1 <ref name="who"></ref> || Amygdalin <ref name="Gleadow_2014"></ref>
|-
| Cherries with pit || 6.5-9.1 <ref name="daenen"></ref> || Amygdalin <ref name="Gleadow_2014"></ref>
|-
| Cherry pits only (black) || 161 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Cherry pits only (red) || 233 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Cherry pits only (morello) || 3900 <ref name="VOLDŘICH_1992" /> || Amygdalin <ref name="VOLDŘICH_1992" />
|-
| Apricot pits, wet weight || 89-2170 (depends on region/variety) <ref name="Chaouali"></ref><ref name="who"></ref> || Amgydalin <ref name="Gleadow_2014"></ref>
|-
| Sweet Apricots with kernel (14-24 fruits for 1 kg; single kernel avg weight is 6 grams <ref name="calapricot">[http://www.califapricot.com/marking_regulations.html California Apricots. Marking Regulations. Retrieved 09/01/16.]</ref>) || 4.2 - 7.2 (avg 0.3 mg per kernel <ref name="wiki_apric_kernel">[https://en.wikipedia.org/wiki/Apricot_kernel "Apricot Kernel". Wikipedia. Retrieved 09/01/2016.]</ref>) || Amygdalin <ref name="Gleadow_2014"></ref>
|-
| Bitter Apricots with kernel (14-24 fruits for 1 kg; single kernel avg weight is 6 grams <ref name="calapricot"></ref>) || 25.2 - 43.2 (avg 1.8 mg per kernel <ref name="wiki_apric_kernel"></ref>) || Amygdalin <ref name="Gleadow_2014"></ref>
|-
| Elderflower (leaves/stems) || 1600 <ref name="nordicfoodlab">[https://web.archive.org/web/20190812014649/http://nordicfoodlab.org:80/blog/2013/10/elder-a-love-story "Elder – a love story". Justine de Valicourt. Nordic Food Lab. 10/03/2013. Retrieved 09/07/2016.]</ref> || Sambunigrin (or sometimes prunasin, holocalin, or zierin) <ref name="elderflowers">[https://www.researchgate.net/publication/233262135_Cyanogenic_Glycosides_from_Sambucus_Nigra Cyanogenic Glycosides from Sambucus Nigra. Marina Dellagreca, Antonio Fiorentino, Pietro Monaco, Lucio Previtera & Ana M. Simonet. 2006.]</ref>
|-
| Elderberries (fully ripe; under-ripe will contain more) || 30 <ref name="nordicfoodlab"></ref> || Sambunigrin (or sometimes prunasin, holocalin, or zierin) <ref name="elderflowers"></ref>
|-
| Peach seeds/kernels || 54-2600 (variety dependent; mostly reported between 54-666) <ref name="VOLDŘICH_1992">[https://www.scopus.com/record/display.uri?eid=2-s2.0-84987336720&origin=inward&txGid=713c7a86664b8d2865e54a25eaafc9b5 Cyanogenesis in Canned Stone Fruits. VOLDŘICH, M., KYZLINK, V. 1992. DOI: 10.1111/j.1365-2621.1992.tb05446.x.]</ref><ref name="Bolarinwa_2014">[https://www.sciencedirect.com/science/article/pii/S0308814613016245 Amygdalin content of seeds, kernels and food products commercially-available in the UK. Islamiyat F. Bolarinwa, Caroline Orfila, Michael R.A. Morgan. 2014. DOI: https://doi.org/10.1016/j.foodchem.2013.11.002.]</ref><ref>[https://www.scopus.com/record/display.uri?eid=2-s2.0-0021674858&origin=inward&txGid=ee159dc998e0469bc88f0685e8d41ecb The cyanide content of laetrile preparations, apricot, peach and apple seeds. Holzbecher, M.D., Moss, M.A., Ellenberger, H.A 1984.]</ref> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Nectarine seeds (summer fire) || 7.2 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Plum seeds (green) || 1050 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Plum seeds (black; firar black) || 600 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Plum seeds (purple; larry anne) || 130 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Plum seeds (yellow; son gold) || 92 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Plum seeds (red; laetitia) || 26 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Apple seeds (royal gala) || 178 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Pear (conference) || 77 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| Non-Rosaceae fruit seeds (courgette, cucumber, marrow, honey dew melon, squash varieties) || 0.6-12.6 <ref name="Bolarinwa_2014" /> || Amygdalin <ref name="Bolarinwa_2014" />
|-
| '''Commercial fruit juices'''
|-
| Lima beans from Burma (white) || 2000-2100 <ref name="who"></ref><ref name="Speijers"></ref> || Linmarin <ref name="soybean"></ref>
|-
| Flaxseed || 910 <ref name="flax">[http://pubs.acs.org/doi/abs/10.1021/bk-1997-0662.ch010 Cyanogenic Glycosides of Flaxseeds. Fereidoon Shahidi and P. K. J. P. D. Wanasundara. 1997.]</ref> || Linamarin, linustatin and neolinustatin <ref name="flax"></ref>
|-
|}
: <nowiki>*</nowiki> Amounts are averages, or are single examples. Actual levels may vary greatly between strains and growth conditions.
See also:
* [https://www.facebook.com/groups/MilkTheFunk/permalink/1401402279887982/ MTF thread on cyanide potential in beer.]
==See Also==
===Additional Articles on MTF Wiki===
* [[Hops#Hop_Derived_Compounds_In_Beer_and_Biotransformations|Hop Biotransformations]]
* [[Brettanomyces]]
* [[Pediococcus]]
* [[Mixed Fermentation]]
* [[Soured Fruit Beer]]
* [[Soured Herb, Spice, and Vegetable Beer]]
===External Resources===
* [https://www.uclouvain.be/cps/ucl/doc/inbr/documents/presentation-jean-marie-rock.pdf "Dry Hopping Myths versus Reality," slideshow by Jean-Marie Rock, ex-brewmaster for Orval.]
* [https://www.uclouvain.be/cps/ucl/doc/inbr/documents/presentation-luk-daenen.pdf "Use of beta-glucosidase activity for flavour enhancement in specialty beers," slideshow by Luk Daenen.]
* [http://nordicfoodlab.org/blog/2013/10/elder-a-love-story "Elder: a love story", by Justine de Valicourt (cyanide in elderberries).]
* [http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0013/111190/prussic-acid-poisoning-in-livestock.pdf Overview of HCN in various grass/straw/hay/livestock feed species.]
* [http://scottjanish.com/?s=glycosides Scott Janish blog articles about glycosides.]
==References==