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updated all occurences of "Pedio" to "Pediococcus"
[[File:Pedio.jpg|thumb|200px|right|Pediococcus - picture taken by Per Karlsson]]
'''Pediococcus''' (often referred to by brewers as ''"Pedio''") are Gram-positive lactic acid bacteria (LAB) used in the production of Belgian style beers where additional acidity is desirable. They are native to plant material and fruits <ref name="ucdavis">[http://wineserver.ucdavis.edu/industry/enology/winemicro/winebacteria/pediococcus_damnosus.html Viticulture & Enology. UC Davis website. Pedioccous damnosus. Retreived 07/28/2015.]</ref>, and often found in spontaneously fermented beer as the primary source of lactic acid production (with ''P. damnosus'' being the only species identified in such beers) <ref>[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095384 The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer. Freek Spitaels, Anneleen D. Wieme, Maarten Janssens, Maarten Aerts, Heide-Marie Daniel, Anita Van Landschoot, Luc De Vuyst, Peter Vandamme. April 18, 2014.]</ref><ref>[[Scientific_Publications#Lambic_and_Spontaneous_Fermentation Multiple Scientific publications linked on MTF.]]</ref>. They are aerotolerant anaerobes, which means they grow anaerobically but can also grow in the presence of oxygen <ref>[http://textbookofbacteriology.net/lactics.html Lactic Acid Bacteria. Todar's Online Texbook of Bacteriology. Kenneth Todar, PhD. Pg 1. Retrieved 08/09/2015.]</ref>. Strains found in beer are hop tolerant <ref>[http://www.biomedcentral.com/1471-2164/16/267 Comparative genome analysis of Pediococcus damnosus LMG 28219, a strain well-adapted to the beer environment. Isabel Snauwaert, Pieter Stragier, Luc De Vuyst and Peter Vandamme. April 2015.]</ref>. Due to their continued metabolism of longer chain polysaccharides, acid production will increase with storage time. ''PedioPediococcus'' can form a [[pellicle]].
''Pediococcus'' may also cause “ropiness” (also called a "sick beer") due to the production of exopolysaccharides. "Ropy" or "sick" beer is more viscous and, in extreme circumstances, can form strands. Sickness effects mostly the mouthfeel and appearance of beer, and may have no influence on the flavor. ''Pediococcus'' species can also produce diacetyl with extended storage time. [[Brettanomyces]] can break down exopolysaccharides and diacetyl produced by ''Pediococcus'' and the two are often used together.
One study showed that optimal growth was observed in [http://www.neogen.com/Acumedia/pdf/ProdInfo/7406_PI.pdf MRS media] with an initial pH of 6.7, and allowed to ferment down to a pH of 4.14 naturally from fermentation. The addition of bacteriological peptone, MnSO4, and Tween 80 also increased activity <ref>[http://www.ncbi.nlm.nih.gov/pubmed/11851822 Nel HA, Bauer R, Vandamme EJ, Dicks LM. Growth optimization of Pediococcus damnosus NCFB 1832 and the influence of pH and nutrients on the production of pediocin PD-1. Department of Microbiology, University of Stellenbosch, Stellenbosch, South Africa. Dec 2001.]</ref>.
Maximum cell densities of ''PedioPediococcus'' and ''Lacto'' are around 50-80 million cells/mL. Since they tend to have high nutrient demands, this number varies based on the conditions of the propogation <ref>[https://www.reddit.com/r/Homebrewing/comments/3qp7b7/advanced_brewers_round_table_neva_parker_white/cwh7iqq Neva Parker, Reddit thread. 10/29/2015.]</ref>.
Although more experiments and probably needed, agitation is believed to be an important factor for any species of microbe (yeast and bacteria). Gentle stirring on a stir plate or orbital shaker, or frequent gentle manual agitation leads to faster growth and a higher number of organisms. Agitation keeps the microbes in solution. It also maximizes the microbes' access to nutrients and disperses waste evenly. In a non-agitated starter, the microbes are limited to the diffusion rate of nutrients, leading to a slower and more stressful growth <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1168024059892473/?comment_id=1174865305875015&reply_comment_id=1176092372418975&total_comments=1&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Conversation with Bryan Heit about starters and agitation. 11/09/2015.]</ref>. Although ''Pediococcus'' are aerotolerant and oxygen usually does not negatively affect their growth, it is also generally not needed. Therefore, it is generally best practice to seal the starter with an airlock.
Some strains of ''P. damnosus'' can cause a beer (or wine) to go "ropy". Reportedly, ropiness in beer that also has ''Brettanomyces'' (which is traditionally credited with breaking down the ropiness after a period of rest) usually lasts anywhere from 1 week to 3 months, although fewer reports claim that it has lasted as long as 7 months (see reference for different experiences of brewers) <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1132030550158491/ Poll on Milk The Funk regarding how long ropy beer has been observed. 08/20/2015.]</ref>. This "ropiness" is actually caused by production of exopolysaccharides (EPS) in the form of β-glucans (beta glucans). A small amount of β-glucan is adequate enough to affect the visible viscosity of beer or wine. The gene known as Dps has been identified with the production of β-glucan/EPS. Not all strains of ''P. damnosus'' express the gene, and only ones that do will cause a beer to go ropy. ''Pediococci'' that are ropy have been found to be more acid, alcohol, and SO2 tolerant than other ''Pediococci''. The thickness of the ropiness is increased with the presence of malic acid <ref name="ESP"></ref>.
One study showed that the production of β-glucan coincided with the end of the growth phase of ''Pediococcus''. While small amounts of β-glucan were produced during growth, after 2 days of growth, β-glucan production increased as growth slowed. β-glucan production stopped when growth stopped. This study showed that β-glucan production is linked to ''Pediococcous'' growth, producing more towards the end of growth. This would explain why beer containing ''PedioPediococcus'' often goes ropy shortly after naturally carbonating in the bottle. This study found that other variables were not factors in the production of β-glucan, such differing levels of alcohol (although alcohol interacts with the β-glucan in a way that makes the viscosity seem thicker). The study also found that the lack of agitation increased the β-glucan production (wine makers will often agitate or aerate ropy wine to cure the wine from ropiness). A higher initial pH encourages higher growth (5.5+), which increases β-glucan production. A lower initial pH (3.5), decreases growth and β-glucan production. A higher concentration of glucose increased growth and β-glucan production. A low starting pH decreases growth, and therefore decreases β-glucan production. Glocuse is needed for β-glucan production. While fructose alone is mostly insufficient, a combination of glucose and fructose was slightly more efficient than glucose alone <ref name="ESP"></ref>.
It has been observed that ''Lactobacillus'' species can produce EPS (''Lactococcus lactis'', ''Lactobacillus delbrueckii'', ''Lactobacillus casei'', and ''Lactobacillus helveticus'') <ref name="ESP"></ref>.