Changes

Hop tolerance can also be encouraged with the availability of organic acids that are used by ''Lactobacillus'' for ATP (energy). [https://www.tandfonline.com/doi/full/10.1080/03610470.2020.1864710?scroll=top&needAccess=true Zheng et al. (2021)] found that many species of ''Lactobacillus'' in an environment containing iso-alpha acids have a higher growth rate when certain organic acids are present. In particular, pyruvate allowed for more growth, but so did other organic acids such as oxalic, tartaric, ketoglutaic, and fumaric acids. Citric acid and acetic acid did not have this positive effect, and acetic acid had a slightly negative effect on cell growth . Without the presence of iso-alpha acids, the additions of organic acids made little difference on the successful growth of ''Lactobacillus'', demonstrating that the presence of organic acids is particularly important when ''Lactobacillus'' is exposed to iso-alpha acids <ref>[https://www.tandfonline.com/doi/full/10.1080/03610470.2020.1864710?scroll=top&needAccess=true Feiyun Zheng, Tianmu Wang, Chengtuo Niu, Yun Jia, Ruilong Zheng, Chunfeng Liu, Jinjing Wang & Qi Li (2021) Proteomic Analysis of Hop Bitter Compound Iso-α-acid Tolerance in Beer Spoilage Lactobacillus casei 2-9-5, Journal of the American Society of Brewing Chemists, DOI: 10.1080/03610470.2020.1864710.]</ref>.