Functional potential and ecology of **Lactobacillaceae** in vegetable fermentations
Fermentation of foods and beverages has been an important biological preservation method for humanity for millennia. In this PhD project, we focused on lactic acid fermentation, and more specifically vegetable fermentations. In vegetable fermentations, a salt-brine is generally added to reduce the growth of spoilage organisms. In most salt-brine vegetable fermentations studied to date, lactic acid bacteria (LAB), particularly members of Lactobacillaceae are the most important fermentation bacteria. This PhD explored three major aspects of LAB-dominated vegetable fermentations: (1) The effect of external factors studied, including vegetable type, salt concentration, and addition of CO2, on the microbial community dynamics. (2) the genomic diversity of the Lactobacillaceae as determined by pangenome analysis. (3) The role of cellulase and carotenoid production by Lactobacillaceae as adaptation factors in vegetable fermentations and other environments. Firstly, we found that most fermentations were characterized by a LAB-dominated community with the genus Leuconostoc as the most abundant genus. Root-associated vegetables, such as beet, carrot, parsnip, and sunroot had the most stable and robust fermentations. Additionally, lower salt concentrations was linked to the presence of less favorable genera of the Enterobacterales order. CO2-addition could mitigate the effect of the low salt concentration, as most Enterobacterales disappeared faster. Secondly, the genomic diversity of the Lactobacillaceae was explored and various unique orthogroups for each species could be detected within their pangenome. These unique orthogroups were used to develop selective and specific strain-specific primers and were validated in situ by tracking starter cultures during carrot juice fermentations. Additionally, this exploration led to the discovery of a novel species called Lactiplantibacillus carotarum, isolated from fermented vegetables. Phenotypically, it was able to metabolize more different carbohydrates compared to the closest relatives, which can be highly present in some fermented vegetable substrates. Lastly, the functional potential of cellulase and carotenoids by Lactobacillaceae isolated from fermented vegetables was explored. These factors were hypothesized to be important for adaptation of the fermented food microorganisms to the vegetable fermentation environment and were verified in vitro. In conclusion, this PhD work contributed to a new understanding of the role of plant substrates, salt, and CO2 in the microbial ecology of vegetable fermentations. We also revealed the potential of the pangenome for vegetable fermentation research. This work incrementally advances our understanding of these man-made ecosystems and might facilitate the development of novel functional foods in a more targeted approach.
Antwerp : University of Antwerp, Faculty of Science, Department of Bioscience engineering , 2023
216 p.
Supervisor: Lebeer, Sarah [Supervisor]
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The publisher created published version Available from 29.03.2026
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Creation 22.04.2024
Last edited 25.04.2024
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