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→Heterolactic
Heterolactic metabolism is described as the cell catabolizing one molecule of glucose into one molecule of CO<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>[https:name="Ciosek_2019" //onlinelibrary.wiley.com/doi/pdf/10.1002/jib.590 Sour beer production: impact of pitching sequence of yeast and lactic acid bacteria. Aneta Ciosek, Iga Rusiecka, Aleksander Poreda. 2019. DOI: https://doi.org/10.1002/jib.590.]</ref>. See [[Lactobacillus#100.25_Lactobacillus_Fermentation|100% ''Lactobacillus'' fermentation]] for more information.
===Categories of Lactobacillus===