People may have seen me post in other threads that fully attenuated (defined as >70% apparent attenuation) 100% Lactobacillus fermentations are not possible and those reported as such were in reality a result of unintentionally introducing yeast. To prove that point, I performed an experiment at Omega Yeast Labs to address the question. Here is what I did: I obtained the two Lacto strains from White Labs (delbrueckii and brevis) and Wyeast (buchneri and brevis), and the Omega L. plantarum strain. I grew them on AOAC plates (a Lactobacillus medium) supplemented with cycloheximide. Propagated the lacto in liquid AOAC at ~90F (no stirring) to maximum cell density (achieved in about 3 days). Pitched 200 mL of these cultures into 2 liters of autoclave-sterilized unhopped wort with a starting gravity of 1.037. Incubated for 2 weeks at ~90F, periodically checking gravity and pH. Final Results: WL brevis: pH 3.14, 1.035 WL delbrueckii: pH 3.72, 1.033 WY brevis: pH 3.72, 1.035 WY buchneri: pH 3.61, 1.034 OYL plantarum: pH 3.17, 1.036 None of the cultures, whether heterofermentative or homofermentative, produced a significant gravity drop. None produced a krausen or obvious CO2 evolution. We're going to send the samples off to be tested for alcohol levels so we can get an idea of how much alcohol the heterofermentative strains produce. I'll update this post when we have those results. Here is the take home message: If you see significant krausen development or gravity drops in your Lacto starters or kettle sours, you have a yeast infection. It's not a result of the Lactobacillus.