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updated 100% Lacto fermentation with bubbles as per Richard Preiss
Lance Shaner's experiment on testing [[100% Lactobacillus Fermentation]] showed that '''pure cultures''' of WLP677, WLP672, Wyeast 5335, Wyeast 5223-PC, and the ''L. plantarum'' from Omega Yeast OYL-605, could not fully attenuate a 1.037 SG wort. The most attenuative ''Lactobacillus'' culture, WLP677, was only able to attenuate down to 1.03255 SG. It is likely that all species and strains of ''Lactobacillus'' available to brewers cannot fully attenuate wort. In addition, this study showed at most a 0.29% ABV in 100% ''Lactobacillus'' fermentations (attributed to WLP677). See [[100% Lactobacillus Fermentation]] for more information. If a higher attenuation is achieved, cross contamination of yeast is most likely the cause.
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 produces any CO2 at all. There have been reliable reports of pure ''Lactobacillusbrevis'' cultures producing layers a layer of bubbles on the surface of wort if roused <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/10838422316439901354678291227048/?comment_id=10921354274813371354678411227036&comment_trackingreply_comment_id=%7B%22tn%22%3A%22R%22%7D 1355288821165995¬if_t=group_comment_reply¬if_id=1468974761019794# Conversation with Richard Preiss on MTF regarding pure Lactobacillus fermentation. 0607/1619/20152016.]</ref>. 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 even with the use of commercially available ''Lactobacillus'' cultures and good sanitation techniques. 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 by yeast.
Elde Arendt, a brewing scientist that specializes in ''Lactobacillus'' presented her work at the Belgian Brewing Conference 2015. In it she explained that LAB will only ferment 0.5°P of wort regardless of the gravity of that wort. When asked at the end of the presentation why ''Lactobacillus'' only ferments ~0.5°P (note that Shaner's experiment shows ''Lactobacillus'' fermenting ~1°P, although this may be due to a margin of error since Shaner only performed this experiment once), considering that ''Lactobacillus'' ferments maltose and there is plenty of maltose in wort, Arendt responded that she believes that the bacteria reaches max cell density in the wort with relatively little sugar requirements (~16 mins in and ~25 mins in):