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During the extended maturation phase, a beer may become "sick" or "ropey", though not all producers get this <ref name="Spontaneous Sour Hour" /> (~1:10 min in) <ref name="Vinnie sour beer talk">[http://www.thebrewingnetwork.com/post1863/ Recording of Vinnie's talk at NHC]</ref> (~1:44 in) <ref name="Vinnie on the Session Jan 2010"/> (~3:44 in). This is the result of exopolysaccharides, which some ''Pediococcus'' strains are known to produce. These exopolysaccharides can be broken down by other microbes present in the beer relieving the beer of its "sickness" (this exopolysaccharide breakdown is generally attributed to ''Brettanomyces''). A beer may also become "sick" in the bottle during bottle conditioning. This is likely due to enhanced ''Pediococcus'' activity from additional fermentable sugar, in the form of simple sugars or beer which has not completely attenuated yet <ref name="Vinnie sour beer talk">[http://www.thebrewingnetwork.com/post1863/ Recording of Vinnie's talk at NHC]</ref> (~1:47 in). A beer which is sick in the bottle will generally clear through the same process as a younger aging beer when given appropriate time. See the [[Pediococcus#.22Ropy.22_or_.22Sick.22_Beer|Pediococcus]] page for more information.
It is worth noting that not all it appears to be possible for spontaneous fermentations contain to not harbor lactic acid bacteria or ''Brettanomyces''. For example, Andy Mitchell from New Belgium Brewing had a homebrewed spontaneous fermentation analyzed by New Belgium's lab after a year of age, and they only found ''Saccharomyces cerevisiae'' var ''diastaticus'' living in the beer and no lactic acid bacteria or ''Brettanomyces''. Andy reported that the beer was also not sour and did not have any ''Brettanomyces'' character <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1879283728766499/ Andy Mitchell. Milk The Funk thread rearding homebrewed batch of spontaneously fermented beer with no ''Brettanomyces'' or LAB. 11/10/2017.]</ref>.
See also [http://www.lambic.info/Microbiology_and_Biochemistry Lambic.info "Microbiology and Biochemistry" wiki page].