Changes

''Lactobacillus'' is generally tolerant of alcohol and high levels of sugar (although growth is diminished once sugar content exceeds 20% due to osmisis osmosis stressing the cell wall). In the presence of high amounts of ethanol, the alcohol tolerant strains pack their cell walls with fatty acids, which slows the fluidity of the cell membrane. The alcohol tolerance of ''Lactobacillus'' is dependent on both strain and the growth substrate, with alcohol tolerance generally higher when glucose or starch are available. In one study that looked at 31 strains of ''Lactobacillus'', all strains grew effectively at 4% ABV. All of them still grew at 10% ABV, although some strains exhibited diffulty difficulty growing effectively at 10% ABV. Growth was diminished in general at 12% ABV (and the few strains that were alcohol intolerant stopped growing), but most still achieved some growth. Eight of the strains tested were still able to exhibit signficant significant growth at 16% ABV, and in general , most strains were able to exhibit at least small growth at 16% ABV (more so on starch and glucose versus cellobiose, lactose, or xylose). In general, the species that were less tolerant of high amounts of ethanol (10-16%) where: ''L. amylovorous'' (1 out of 4 strains was particularly intolerant), ''L. hilgardii'' (1 strain still grew at 16% ABV, but less than the others), ''L. pentosus'' (1 strain still grew on starch medium, but not on glucose above 10% ABV), and ''L. casei'' (most strains grew in most growth media, but generally less than other species). In general, the strains of ''L. brevis'' and ''L. plantarum'' were more tolerant of high ABV concentrations <ref>[https://link.springer.com/article/10.1007/BF01583633 Ethanol tolerance and carbohydrate metabolism in lactobacilli. R. Shane GoldM. M. MeagherR. HutkinsT. Conway. 1992.]</ref>. Peyer et al. (2017) examined the effects of the sugar content of brewer's wort on a strain of ''Lactobacillus amylovorous''. They found that the higher gravity of the wort increased the growth of the ''Lactobacillus'', and therefore also the lactic acid production. This increase was linear until the extract reached 16%, at which time the growth increase began to slow down. The higher growth and more lactic acid production in higher gravity wort was probably due to increased nutrients as well as a higher buffer capacity. This growth increase plateaued in wort that had 18-20% sugar content, which was likely due to osmotic stress on the cells <ref name="peyer_2017">[http://www.asbcnet.org/publications/journal/vol/2017/Pages/ASBCJ-2017-3861-01.aspx Sour Brewing: Impact of Lactobacillus amylovorus FST2.11 on Technological and Quality Attributes of Acid Beers. Lorenzo C. Peyer, Martin Zarnkow, Fritz Jacob, David P. Schutter, Elke K. Arendt. 2017.]</ref>.