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[[Brettanomyces]], [[Lactobacillus]], and [[Pediococcus]] can produce forms of ''Tetrahydropyridine''. In Brettanomyces, THP is ATHP and ETHP are produced by metabolizing the amino acids L-Lysine and D-Lysine, along with and ethanol. Oxygen has a stimulatory effect in it's production , but this is probably because ''Brett'' has a higher biomass formation under aerobic conditions <ref>[http://www.brettanomycesproject.com/dissertation/introduction/ Yakobson, Chad. The Brettanomyces Project; Introduction. Retrieved 3/10/2015.]</ref><ref>[http://pubs.acs.org/doi/abs/10.1021/jf071243e The Role of Lysine Amino Nitrogen in the Biosynthesis of Mousy Off-Flavor Compounds by Dekkera anomala. Paul R. Grbin, Markus Herderich, Andrew Markides, Terry H. Lee, and Paul A. Henschke. J. Agric. Food Chem., 2007.]</ref><ref name="Oelofse">[http://www.sawislibrary.co.za/dbtextimages/OelofseA2.pdf Significance of Brettanomyces and Dekkera during Winemaking: A Synoptic Review. A. Oelofse, I.S. Pretorius, and M. du Toit. 2008.]</ref>. The level of THP production varies widely between species and strains of ''Brett'', with some strains not producing it at all and some producing very high amounts above taste threshold. Additionally, THP production in the presence of higher glucose and fructose levels, which explains why THP may be seen more often in stuck wine fermentations than wine that has finished fermenting <ref>[http://www.ncbi.nlm.nih.gov/pubmed/18194246 Growth and volatile compound production by Brettanomyces/Dekkera bruxellensis in red wine. Romano A, Perello MC, de Revel G, Lonvaud-Funel A. J Appl Microbiol. 2008 Jun.</ref>. ATHP is further metabolized into 2-ethyltetrahydropyridine (ETHP/ETPY) by Brettanomyces, although not much is known about this metabolic process <ref>[http://ucce.ucdavis.edu/files/repositoryfiles/Joseph_5_Aromatic_Diverswity_of_Brettanomyces-82350.ppt Joseph, C.M. Lucy. ''Aromatic Diversity of Brettanomyces''. U.C. Davis. Retrieved 3/10/2015.]</ref>. The presence of the "mousy off-flavor" caused by THP appears to be temporary in beer. Although not much is known about the degradation or metabolic break down of THP, it tends to age out of beer after 2-3 months.

Heterofermentative [[Lactobacillus]] spp. can also produce ATHP and is further metabolized into 2-ethyltetrahydropyridine (ETHP from Lysine and ethanol /ETPY) by Brettanomyces, although not much is known about this metabolic process <ref>Sparrows[http://ucce.ucdavis.edu/files/repositoryfiles/Joseph_5_Aromatic_Diverswity_of_Brettanomyces-82350.ppt Joseph, JeffC.M. Lucy. ''Wild BrewsAromatic Diversity of Brettanomyces''. Brewers PublicationsU.C. 2005Davis. Pg. 112Retrieved 3/10/2015.]</ref><ref>[https://books.google.com/books?id=tFjsAuo5WocC&pg=PA348&lpg=PA348&dq=lactobacillus+Tetrahydropyridine&source=bl&ots=QUVyoFtIwK&sig=h1cdjB0r1pIRX2Bms8wVA0UiLk4&hl=en&sa=X&ei=4DX_VPz5CsH6oQSAzoGgBA&ved=0CEwQ6AEwCQ#v=onepage&q=lactobacillus%20Tetrahydropyridine&f=false Lahtinen, Ouwehand, Salminen ETHP has a significantly higher taste threshold, von Wright. Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition. Pg 348.]is often not detected in contaminated wine </refname="Oelofse"><ref>[http://ajevonline.org/content/37/2/127.short Heresztyn, Tamila. Formation of Substituted Tetrahydropyridines by Species of Brettanomyces and Lactobacillus Isolated from Mousy Wines.]</ref>.

The presence of the "mousy off-flavor" caused by THP appears to be temporary in beer. Although not much is known about the degradation or metabolic break down of THP, it tends to age out of beer after 2-3 months. Another unknown is why does ''Brett'' produce THP shortly after kegging and force carbonating a beer that has reached final gravity. Pitching fresh ''Saccharomyces'' for bottle conditioning a beer with ''Brett'' in it has reportedly reduced THP production, perhaps through the quicker metabolism of both the oxygen and sugar that is introduced during packaging time.  Heterofermentative [[Lactobacillus]] spp. can also produce ATHP and ETHP from Lysine and ethanol <ref>Sparrows, Jeff. ''Wild Brews''. Brewers Publications. 2005. Pg. 112.</ref><ref>[https://books.google.com/books?id=tFjsAuo5WocC&pg=PA348&lpg=PA348&dq=lactobacillus+Tetrahydropyridine&source=bl&ots=QUVyoFtIwK&sig=h1cdjB0r1pIRX2Bms8wVA0UiLk4&hl=en&sa=X&ei=4DX_VPz5CsH6oQSAzoGgBA&ved=0CEwQ6AEwCQ#v=onepage&q=lactobacillus%20Tetrahydropyridine&f=false Lahtinen, Ouwehand, Salminen, von Wright. Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition. Pg 348.]</ref><ref>[http://ajevonline.org/content/37/2/127.short Heresztyn, Tamila. Formation of Substituted Tetrahydropyridines by Species of Brettanomyces and Lactobacillus Isolated from Mousy Wines.]</ref>. Some species of [[Pediococcus]] have been associated with the production of ATHP. In particular, these include ''P. pentosaceus'' <ref>[http://www.uniprot.org/uniprot/Q03HT0 UniProt article. Retrieved 3/10/2015.]</ref><ref>[http://www.uniprot.org/uniprot/U5ZF76 UniProt article. Retrieved 3/10/2015.]</ref>, and ''P. clausenii'' <ref>[http://www.uniprot.org/uniprot/G8PEU4 UniProt article. Retrieved 3/10/2015.]</ref> (note that commercial cultures of [[Pediococcus]] are normally ''P. damnosus'').