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==Production in Beer and Wine==
''[[Brettanomyces]] '' can create isovaleric acid <ref name="wikipedia">[http://en.wikipedia.org/wiki/3-Methylbutanoic_acid Wikipedia article]</ref>. The compound generally takes a few months to produce in beer by ''Brettanomyces''. ''Brettanomyces '' breaks down leucine present in beer into isovaleric acid (controversial, but generally accepted) <ref>[https://scholar.sun.ac.za/bitstream/handle/10019.1/4141/Botha,%20J.J.pdf?sequence=1 Botha, Janita J. Sensory, chemical and consumer analysis of ''Brettanomyces '' spoilage in South African wines. March 2010. Pg 2, 13, 17, 18]</ref><ref>[https://scholar.sun.ac.za/bitstream/handle/10019.1/1239/oelofse_investigating_2008.pdf?sequence=1 Oelofse, Adriaan. Investigating the role of ''Brettanomyces '' and Dekkera during winemaking. December 2008.]</ref>.
Isovaleric acid can also be produced by a bacteria that lives naturally on human skin and is responsible for foot odor called Staphylococcus epidermidis. It does so by degrading leucine, an amino acid present in sweat <ref>[http://www.ncbi.nlm.nih.gov/pubmed/16699586 Ara K, Hama M, Akiba S, Koike K, Okisaka K, Hagura T, Kamiya T, Tomita F. Can J Microbiol. 2006 Apr.]</ref>. Leucine is also present in beer <ref>[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1981.tb03992.x/pdf Hall, Nutfield, Redhill, Surrey. Amino Acid Esters in Beer. Brewing Research Foundation. July 14, 1980.]</ref>.