13,703
edits
Changes
added biochemistry to Cell Growth section
[[File:Omega-lacto-microscope.jpg|thumb|Omega Yeast Labs OYL-605 Lactobacillus Blend; photo by [https://www.facebook.com/groups/MilkTheFunk/permalink/1096077917087088/ Stephen Little].]]
'''Lactobacillus''' (often referred to by brewers as "Lacto") is a genus of Gram-positive, rod-shaped lactic acid bacteria (LAB) which produces acidity and sour flavors in the form of lactic acid (and sometimes acetic acid) found in lambics, Berliner Weiss, sour brown ales, and gueuze. All ''Lactobacillus'' species are aerotolerant facultative anaerobes, which means they grow anaerobically but can also grow in the presence of oxygen and use oxygen to some degree <refname="todar_lactics4">[http://textbookofbacteriology.net/lactics.html Lactic Acid Bacteria. Todar's Online Texbook of Bacteriology. Kenneth Todar, PhD. Pg 1. Retrieved 08/09/2015.]</ref>. There are more than 100 species, many of which are found in the human gastrointestinal track <refname="todar_lactics4">[http://textbookofbacteriology.net/lactics_4.html ''Lactic Acid Bacteria''. Todar's Online Texbook of Bacteriology. Kenneth Todar, PhD. Pg. 4. Retrieved 07/28/2015.]</ref><refname="Todar_nutgro4>[http://textbookofbacteriology.net/nutgro_4.html ''Nutrition and Growth of Bacteria''. Todar's Online Texbook of Bacteriology. Kenneth Todar, PhD. Retrieved 07/28/2015.]</ref>. In addition to beer, some species of ''Lactobacillus'' are also used to ferment yogurt, cheese, sauerkraut, pickles, wine, cider, kimchi, cocoa, and kefir <ref>[https://en.wikipedia.org/wiki/Lactobacillus ''Lactobacillus''. Wikipedia. Retrieved 07/28/2015.]</ref>. ''Lactobacillus'' can form a [[pellicle]] (need reference). See [[Pediococcus]], [[Brettanomyces]], [[Saccharomyces]], and [[Mixed Cultures]] charts for other commercially available cultures. See the [[Sour Worting]] and [[Mixed Fermentation]] pages for brewing techniques with ''Lactobacillus''. See the [[Alternative Bacteria Sources]] section for culturing ''Lactobacillus'' from grains, yogurt, probiotics, and other sources.
==Commercial Lactobacillus Cultures==
Most ''Lactobacillus'' species have a thermal death rate of ~145°F (63°C). Freezing without glycerol will kill most cells, but it is possible for a very small number of cold-resistant mutant cells to survive <ref>[http://fermentationnation.net/2015/11/episode-26-quality-assurance-w-jessica-davis-of-the-bruery/ Fermentation nation Podcast interview with Jessica Davis, QA for The Bruery.</ref> (~1:19:00 in).
All [https://en.wikipedia.org/wiki/Prokaryote prokaryotes], which includes all bacteria in general, are categorized based on the levels of oxygen in their environment in which they can grow and how they utilize oxygen if at all <ref name="todar_nutgro4"></ref>. ''Lactobacillus'' species are usually considered to be "facultative anaerobes" (or "facultative aerobes") <ref name="todar_lactics4"></ref>. Facultative anaerobes make energy from oxygen if it is present via the [https://en.wikipedia.org/wiki/Oxidative_phosphorylation oxidative phosphorylation pathway], but otherwise engage in anaerobic fermentation <ref>[http://www.ncbi.nlm.nih.gov/books/NBK21208/ Biochemistry. 5th edition. Berg JM, Tymoczko JL, Stryer L. 2002. Chapter 18.]</ref><ref>[http://inst.bact.wisc.edu/inst/index.php?module=book&type=user&func=displayarticle&aid=111 Virtual Microbiology Textbook. Department of Bacteriology, University of Wisconsin-Madison. Retrieved 12/02/2015.]</ref>. ''Lactobacilli'', however, are unique in that they blur the line between facultative anaerobes and another class of prokaryotes known as aerotolerant anaerobes (anaerobes that do not use oxygen to generate energy, but can grow in the presence of oxygen). They can utilize oxygen, but not through the oxidative phosphorylation pathway. They use an alternative pathway instead. This pathway uses flavine-containing oxidases and peroxidases to carry out the oxidation of NADH2 using O2. ''Lactobicalli'' then are a somewhat special case of facultative anaerobes <ref>Correspondence with Bryan Heit from Dan Pixley. 12/01/2015.</ref>. The important take away here is that ''Lactobacillus'' do not care if oxygen is present in order to grow and produce energy for themselves and lactic acid for brewers.
====Hop Tolerance====