Changes

''P. damnosus'' can produce high amounts of diacetyl during lactic acid production <ref>[http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2672.2000.00956.x/pdf Identification of pediococci by ribotyping. R. Satokari, T. Mattila-Sandholm and M.L. Suihko. Journal of Applied Microbiology 2000, 88, 260–265.]</ref><ref>[http://mmbr.asm.org/content/77/2/157.full The Microbiology of Malting and Brewing. Nicholas A. Bokulicha, and Charles W. Bamforth. June 2013.]</ref>. Diacetyl is the 'buttery' aroma and flavor found in beer (generally not favorable) and in wine (favorable in amounts between 1-4 mg/L) . While other microbes found in beer and wine fermentation (namely ''Saccharomyces cerevisiae'') can also produce diacetyl, ''Pediococcus'' and other lactic acid bacteria are known to be able to produce much higher amounts <ref name="Wade_2018" />. In lactic acid bacteria, diacetyl can be the byproduct of both homofermentative metabolism of sugars as well as the metabolism of citric acid, and it is a way for the cells to regenerate NADP⁺. In either of these two pathways, extra pyruvate is turned into alpha-acetolactate which then undergoes an oxidative decarboxylation reaction to produce diacetyl. Diacetyl is often reduced by yeast to acetoin and/or 2,3-butanediol, which have a higher threshold and less of an impact on the finished beer/wine <ref name="Wade_2018" />. In mixed fermentation sour beer, the breakdown of diacetyl into acetoin and 2,3-butanediol is often thought to be carried out by ''Brettanomyces''.