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'''Before ''' getting started making a sour beer, we recommend reading these resources. It is also recommended that you understand the basics of brewing before getting started into sour beer brewing.* The book "American Sour Beers:Innovative Techniques for Mixed Fermentations," by Michael Tonsmeire. This book is very friendly for brewers who are new to mixed fermentation brewing. This is probably a better resource to begin with before diving deep into this wiki. * This wiki! Specifically, these pages: [[FAQ]], [[Mixed Fermentation]], [[Wort Souring]], [[Gose]], [[Berliner Weissbier]], [[Mixed Cultures]], [[Alternative Bacteria Sources]], [[Lactobacillus]], and [[Brettanomyces]].* The book "American Sour Beers: Innovative Techniques for Mixed Fermentations," by Michael Tonsmeire.

When brewing sour beer, there are a few more players to the “yeast” side of the ingredients list. In addition to ''Saccharomyces'' or “Sacch”, which is commonly referred to as "brewers yeast", in wild beer brewing the brewer is also often dealing with ''Brettanomyces'', which is another genus of yeastthat is closely related to ''Saccharomyces''. ''Brettanomyces'' yeasts produces novel fruity and sometimes funky flavors often over a long period of slow fermentation. Bacteria are used to produce sourness in the form of lactic acid. These bacteria are called "lactic acid bacteria", and or "LAB" for short. Specifically, they are ''Lactobacillus'' and ''Pediococcus'', which are both . Other bacteria. such as ''Acetobacter'' (acetic acid bacteria) and ''enterobacterEnterobacter'' do (enteric bacteria) sometimes play a part in some sour fermentations, however , they are not often intentionally added.

===''Brettanomyces''===There are two major species of ''Brettanomyces''used in brewing: ''B. Bruxellensisbruxellensis'' and ''B. Anomalaanomalus''(sometimes called "Brett claussenii" by yeast labs). Despite other strains mentioned, there are only five species of Brett, with these two being the species most commonly used in brewing. ''Brettanomyces'' produces a lot of fruity esters that are pleasurable in beer. It also produces what we will later refer to as the “funk” when it comes to wild beers. While it is capable of producing some acetic acid when in the presence of oxygen (think vinegar), funk is what is typically described. Despite providing desired esters, funk , and a little bit of acetic acid, it is important to note that ''Brettanomyces'' can also be responsible for less desired flavors: feet, hard boiled egg, and some solvent-like nail polish flavors.Pure commercial cultures of ''Brettanomyces '' are available at most yeast suppliers(see [[Brettanomyces#Commercial_Cultures||''Brettanomyces'' cultures]] for a comprehensive list). ''Brettanomyces''does NOT provide a universal flavor. Just like the various ''Saccharomyces'' strains most brewers are familiar with, each ''Brettanomyces'' strain can produce a vast array of different flavors, depending on the particular strain, temperature and time.

===''Lactobacillus''===''Lactobacillus'' is a rod shaped bacteria that can grow with or without oxygen and produces lactic acid - most people are familiar with the sourness found in yogurt, sauerkraut , pickles, and so on. ''Lactobacillus'' converts sugars to lactic acid (and sometimes CO2 and ethanol). It can produce varying complexities of sourness from the one dimensional to the more complex, depending on which type is used.

===''Pediococcus''===''Pediococcus'' is a bacteria that also produces lactic acid, although generally slower than ''lactobacillusLactobacillus'' (''P. pentosaceus'' from Bootleg Biology's "Sour Weapon P" culture is an exception; this culture is good for kettle souring and other fast souring brewing methods). The sourness tends to be thought of as more aggressive than ''Lactobacillus''and is often thought to produce more of a complex sourness. It can also produces sometimes produce off flavors (diacetyland "ropiness", which turns the beer into the thickness of syrup) so it needs to have something to help clean up any unwanted flavors – like ''Brettanomyces'', which converts it to other compounds with less aggressive flavors. There is some discussion that ''Pediococcus'' thought of “complexity” is merely perceived by brewers because it works longer than ''Lactobacillus''does. This “complexity” could be simply because ''Pediococcus'' can lower the pH more than ''Lactobacillus''.

Also called "a real sour", this is where multiple microorganisms are pitched into the fermenter and aged for many months in order to produce a sour beer.