Other factors can determine if a ''facultative heterofermentative'' species uses ''homolactic'' or ''heterolactic'' fermentation. For example, L. plantarum, which is a ''facultatively heterofermentative'' species, is ''homolactic'' without the presence of oxygen. In the presence of oxygen, however, it performs ''heterolactic'' fermentation, and produces acetic acid <ref>[https://microbewiki.kenyon.edu/index.php/Lactobacillus_plantarum_and_its_biological_implications Lactobacillus plantarum and its biological implications. Microbe Wiki. Retrieved 6/7/2015.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1083842231643990/?comment_id=1084922688202611&offset=0&total_comments=28&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Lance Shaner about L. plantarum on MTF. 6/7/2015.]</ref>.
It is worth noting that the ====100% Lactobacillus Fermentation==== The amount of CO2 produced is very small in ''heterofermentative'' species. Lance Shaner of Omega Yeast Labs noted that although L. brevis is classified as ''obligatory heterofermentative'', the human eye cannot detect any CO2 production in the Omega Yeast Lactobacillus blend (OYL-605). Lance still needs to test this blend to see if it does produce any CO2. It is clear though that any type of ''Lactobacillus'', regardless of whether it is ''heterofermentative'' or ''homofermentative'', cannot produce a krausen. Krausens are sometimes seen with the use of commercially available ''Lactobacillus'' cultures. If a krausen develops in wort when it is the only culture that is pitched, this is indicative of cross contamination of ''Saccharomyces'' or ''Brettanomyces'' in either the wort, or the ''Lactobacillus'' culture itself <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1083842231643990/?comment_id=1084646124896934&offset=0&total_comments=26&comment_tracking=%7B%22tn%22%3A%22R8%22%7D Discussion with Lance Shaner on MTF. 6/7/2015.]</ref>. In addition to this, ''heterolactic'' fermentation by ''Lactobacillus'' can only produce 10-20% of the ethanol that Saccharomyces can produce <ref name="PhysioLacto">[http://phdinbeer.com/2015/04/13/physiology-of-flavors-in-beer-lactobacillus-species/ Humbard, Matt. Physiology of Flavors in Beer – Lactobacillus Species. Retrieved 6/14/2015.]</ref>, therefore a high level of attenuation cannot be achieved by ''Lactobacillus'' and is again a sign of cross contamination of yeast.
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