From phyllosphere to fermentation: Impact of fermentation scale and temperature on sauerkraut fermentation.

The spontaneous fermentation of vegetables such as kimchi, pao cai and sauerkraut, relies on lactic acid bacteria (LAB) from the plant phyllosphere. Plant-associated LAB occur only at low abundance. This study investigated the impact of fermentation scale, temperature and cabbage source on the LAB diversity. Fermentations were conducted at a scale of 0.8 g to 30 g by immersion of chopped interior leaves of white cabbage obtained from two supermarkets, SF and SW, in 2.5 % (w/w) NaCl solution at 10 °C and 20 °C. Fermentations were monitored by pH determination, metabolite analysis and microbial cell counts, and by 16S rRNA gene amplicon sequencing. Fermentation of 0.8 g cabbage SF with 20 replicates per group supported growth of Enterobacterales but not of LAB. Cabbage SW was fermented by Leuconostoc spp., with an average relative abundance of 98.8 % after 28 d. In fermentations with 8 g cabbage, Lactiplantibacillus established as dominating fermentation microorganism. At the 30 g scale, Lactiplantibacillus dominated at 20 °C regardless of cabbage source, whereas Leuconostoc or Rahnella remained dominant at 10 °C. The organic acid concentrations and the metabolism of phenolic compounds differed depending on whether Lactiplantibacillus, Leuconostoc or Rahnella were the predominant fermentation microorganisms. Collectively, our data highlight that the establishment of LAB communities in sauerkraut fermentation is influenced by both the fermentation scale and temperature, underscoring the critical roles of Lactiplantibacillus at higher temperatures and Leuconostoc at lower temperatures.