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====Effects on Mixed Fermentation====
The presence of ''Lactobacillus'' can stall or slow yeast fermentation. This is likely a combination of low pH. The presence of lactic acid might change the way yeast ferments by allowing them to consume multiple types of sugars regardless of whether or not glucose is present, although it has been demonstrated that this alone is not the cause for stuck fermentations (see [[Lactic Acid]] for more information). Another study compared beer pre-soured with''L buchneri'' versus pre-soured with lactic acid versus lactic acid added post yeast fermentation and found that lactic acid did not significantly change the amount of volatile esters produced by the yeast strain tested (Fermentis US-05), however, the beers soured with ''L. buchneri'' had significantly different volatile ester compounds compared to the beers with just lactic acid added to them. This supports anecdotal reports from brewers that adding lactic acid to beer to make a sour beer does not produce the same beer than when the souring is done with ''Lactobacillus'' <ref name="Dysvik_2019">[https://onlinelibrary.wiley.com/doi/10.1002/jib.569 Pre‐fermentation with lactic acid bacteria in sour beer production. Anna Dysvik, Kristian Hovde Liland, Kristine S. Myhrer, Bjørge Westereng, Elling‐Olav Rukke, Gert de Rouck, Trude Wicklund. 2019. DOI: https://doi.org/10.1002/jib.569.]</ref>.
Peyer et al. (2017) observed that growth of US-05 was 82% at a pH of 3.51, and 53% at a pH of 3.17. Fermentation was delayed by 2-4 days (the lower the pH, the longer the start of fermentation was delayed). In a co-fermentation of ''Lactobacillus amylovorus'' and US-05, the initial growth of the ''L. amylovorus'' continued for 3 days while the US-05 was delayed. On day 7, the US-05 recovered and continued growth, and the growth of the ''Lactobacillus'' was slowed starting on day 5. This was due to the increase in ethanol from fermentation, lower pH, and the depletion of nutrients for the ''Lactobacillus''. It is also possible that the yeast benefited from the autolysis of the ''Lactobacillus'', which is speculated to have released nutrients that were made available to the yeast <ref name="Peyer_2017" />. Santeri Tenhovirta's master thesis agreed with this. Tenhovirta pitched several species of ''Lactobacillus'' for 48 hours, and then pitched Fermentis US-05. The control US-05 fermentation without any ''Lactobacillus'' started to ferment as expected after 20 hours, while the samples that were pre-acidified with ''Lactobacillus'' took around 2 days to begin yeast fermentation <ref name="Tenhovirta_masters">[https://helda.helsinki.fi/handle/10138/303018 The Effects of Lactic Acid Bacteria Species on Properties of Sour Beer. Santeri Tenhovirta; master thesis in Food Science from the University of Helsinki. 2019.]</ref>.