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updated section on LAB and gamma-aminobutyric acid
===Lactic Acid Bacteria===
''[[Lactobacillus]]'' and other LAB produce butyric acid by breaking down lipids to fats. The low level of lipids in brewer's wort most likely limits butyric acid to insignificant levels in beer production. Butyric acid production by ''Lactobacillus'' is more significant in milk based fermented products such as yogurt and cheese <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1182597671768445/?qa_ref=qd&comment_id=1182773928417486&reply_comment_id=1183242405037305&comment_tracking=%7B%22tn%22%3A%22R7%22%7D Conversation with Bryan of Sui Generis Blog on MTF regarding butyric acid production by Lactobacillus. 11/23/2015.]</ref>. For example, one study on a strain of ''L. plantarum'' that was fermented in three different substrates (oats, barley, and wheat) showed no production of butyric acid <ref>[http://www.sciencedirect.com/science/article/pii/S0308814609004373 Volatile compounds produced by the probiotic strain Lactobacillus plantarum NCIMB 8826 in cereal-based substrates. Ivan Salmeron, Pablo Fuciños, Dimitris Charalampopoulos, Severino S. Pandiella. 2009.]</ref>. Due to the low amount of lipids in wort, compounds from the reduction of lipids in grain fermentations by lactic acid bacteria have not been studied <ref name="peyer_review">[http://www.sciencedirect.com/science/article/pii/S0924224415300625 Lactic Acid Bacteria as Sensory Biomodulators for Fermented Cereal-Based Beverages. Lorenzo C. Peyer , Emanuele Zannini , Elke K. Arendt. 2016.]</ref>.
Note that much research has been done on the production of γ-amino butyric acid (also called "gamma-aminobutyric acid" or "GABA" for short) by various bacteria species due to its health benefits. ''Lactobacillus brevis'', ''L. plantarum'', and a few other species of bacteria are able to produce GABA from the non-protein amino acid glutamate via the enzyme glutamate decarboxylase. GABA (C<sub>4</sub>H<sub>9</sub>NO<sub>2</sub>) has a different chemical formula and is a different compound than butyric acid (C<sub>3</sub>H<sub>7</sub>COOH) <ref>[https://en.wikipedia.org/wiki/Gamma-Aminobutyric_acid "Gamma-Aminobutyric Acid". Wikipedia. Retrieved 06/11/2018.]</ref><ref>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3769009/ Production of gaba (γ – Aminobutyric acid) by microorganisms: a review. Radhika Dhakal, Vivek K. Bajpai, and Kwang-Hyun Baek. 2012.]</ref>. GABA reportedly smells "savory" or "meaty" <ref>[http://www.thegoodscentscompany.com/data/rw1198861.html "gamma-aminobutyric acid". The Good Scents Company. Retrieved 06/11/2018.]</ref>. Therefore, the information regarding the production of GABA by ''Lactobacillus'' species should not be confused with butyric acid.
===Other Microbes===