Characterization\nof Key Lipid Components in the Cell\nMembrane of Freeze-Drying Resistant Lacticaseibacillus\nparacasei Strains Using Nontargeted Lipidomics

Lactic acid bacteria (LAB) are usually freeze-dried into\npowder\nfor transportation and storage, with the bacterial membrane playing\na crucial role in this process. However, different strains exhibit\ndifferent levels of freeze-drying resistance in their cell membranes.\nIn this study, Lacticaseibacillus paracasei (L. paracasei) strains 1F20, K56,\nand J5, demonstrating survival rates of 59.51, 25.86, and 4.05% after\nfreeze-drying, respectively, were selected. The membrane structure\nand composition of these strains were subsequently analyzed. Bacterial\nlive/dead staining results indicated that strain 1F20 maintained the\nhighest membrane integrity after drying. Nontargeted lipidomics analysis\nrevealed six differential lipid species that differed in membrane\nlipid compositions. KEGG functional enrichment analysis revealed 13\nsignificantly different pathways, with glycerophospholipid metabolism\nbeing the most critical. This study explored the membrane composition\nof L. paracasei at the cellular level\nand identified key lipid species associated with freeze-drying resistance,\nproviding a reference for screening highly resistant strains.