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added Ciosek et al (2019) data
This study also compared two pre-soured beers with ''L buchneri'' where one was boiled and hopped after souring and the other was not boiled but instead blended with hoppy wort before fermentation (the viability of the ''L. buchneri'' was greatly reduced in the beer that was blended with hoppy wort, but not completely killed as was the case for the kettle soured beer). The beer that was blended with hoppy wort ended up having the most acetic acid (still below threshold), and the highest level of fruity tasting esters: ethyl heptanoate and ethyl octanoate, indicating that if the ''Lactobacillus'' is allowed to live then it can contribute to more complexity over time. There were no differences in any of the beers as far as ethanol production or CO<sub>2</sub> production, and terminal acid shock did not occur (probably because the beers were only 4% ABV and 3.6 pH as opposed to the 8.4% ABV and 3.17 pH of the beer tested in the [[Saccharomyces#Fermentation_Under_Low_pH_Conditions|terminal acid shock study by Rogers et al.]]). It is important to note that the overall sensory differences reported in this study between the beers soured with ''L. buchneri'' and the beers soured with lactic acid were minor from a statistical analysis point of view <ref name="Dysvik_2019" />.
Also found in the Peyer study was an increase in [https://en.wikipedia.org/wiki/Diacetyl diacetyl] and [https://en.wikipedia.org/wiki/Acetoin acetoin] in the beers that were co-fermented with ''L. amylovorus'' and US-05 versus the beers that were kettle soured or mash soured. Both of these compounds are responsible for the buttery taste in beer. Normally, after primary fermentation the yeast reduces diacetyl to acetoin, which is then converted to butanediol, however during a co-fermentation with ''Lactobacillus'', this conversion was inhibited in this study <ref name="Peyer_2017" />.
====Heterolactic====
Heterolactic metabolism is described as the cell catabolizing one molecule of glucose into one molecule of CO2CO<sub>2</sub>, one molecule of glyceraldehyde phosphate, and one molecule of acetyl phosphate. The molecule of glyceraldehyde phosphate is reduced to one molecule of lactate, and the acetyl phosphate is reduced to one molecule of ethanol (or one molecule of acetic acid instead of ethanol, depending on its growing environment <ref name="Raunak">[https://raunakms.wordpress.com/2011/01/30/lactic-acid-bacteria/ Lactic Acid Bacteria. Raunak Shrestha. Retrieved 6/7/2015.]</ref>). Heterolactic fermentation allows the fermentation of hexoses and pentoses <ref>[https://books.google.com/books?id=eZjIfud742wC&pg=PA33&lpg=PA33&dq=facultative+heterofermentative&source=bl&ots=QQYpzpsrvC&sig=kkyP7wUjgWiE2UV2qkIaRyxMMGA&hl=en&sa=X&ei=K_d0VYDJPLX9sATv_IXgAQ&ved=0CDIQ6AEwBDgK#v=onepage&q=facultative%20heterofermentative&f=false Handbook of Dough Fermentations. Karel Kulp, Klaus Lorenz. CRC Press, May 20, 2003. Pg 33.]</ref>. Heterolactic fermentation follows the Phosphoketolase Pathway, which is a branch of the Pentose Phosphate Pathway (also called the "Phosphogluconate Pathway") <ref name="Effects on Food Properties"></ref><ref>[https://books.google.com/books?id=ZKzzCAAAQBAJ&pg=PA157&lpg=PA157&dq=is+Pentose+Phosphate+Pathway+pathway+the+same+as+phosphoketolase+pathway&source=bl&ots=5-uJY2vpKx&sig=Q-2yFtjWIXGXQnZvgvWZ66OayGc&hl=en&sa=X&ved=0ahUKEwix0fmi64HKAhUI82MKHQMzDcsQ6AEINTAE#v=onepage&q=is%20Pentose%20Phosphate%20Pathway%20pathway%20the%20same%20as%20phosphoketolase%20pathway&f=false Understanding Bacteria. S. Srivastava. 2013. Pg 157.]</ref><ref>[http://textbookofbacteriology.net/metabolism_3.html Todar's Online Textbook of Bacteriology. Diversity of Metabolism in Procaryotes (page 3). Retrieved 12/29/2015.]</ref><ref>[https://books.google.com/books?id=CKEgLmqfbRQC&pg=PA180&lpg=PA180&dq=is+Pentose+Phosphate+Pathway+pathway+the+same+as+phosphoketolase+pathway&source=bl&ots=p_01NAx1Aq&sig=wijMw9u4nBJ2oiH0JjHZfSxrgPU&hl=en&sa=X&ved=0ahUKEwix0fmi64HKAhUI82MKHQMzDcsQ6AEIMjAD#v=onepage&q=is%20Pentose%20Phosphate%20Pathway%20pathway%20the%20same%20as%20phosphoketolase%20pathway&f=false Microbiology. Daniel V. Lim. 2003. Pg 180.]</ref>. When different substrates are available to heterolactic fermenting ''Lactobacillus'', such as fructose or oxygen, acetate (acetic acid) can be produced instead of ethanol <ref name="Peyer"></ref>. It has been observed for at least one strain of ''L. brevis'', which only performs heterolactic fermentation, that the amount of CO<sub>2</sub> produced by this fermentation in brewer's wort was negligible. This is most likely due to the small amount of sugar consumed by ''Lactobacillus'' <ref name="Ciosek_2019" />. See [[Lactobacillus#100.25_Lactobacillus_Fermentation|100% ''Lactobacillus'' fermentation]] for more information.
===Categories of Lactobacillus===