Abstract:The effects of different cryoprotectants on the metabolic pathways of freeze-dried Lactobacillus plantarum dy-1 (L. P dy-1) powder during fermentation were analyzed through a metabolomics study. The intracellular metabolites of L. P dy-1 were separated and analyzed by gas chromatography-mass spectrometry. The metabolites produced in the presence of the different cryoprotectantss were identified and analyzed by using pattern recognition and partial least squares methods, and were employed to reconstruct the metabolic pathways using the Kyoto Encyclopedia of Genes and Genomes database. The results indicated that 10% inulin, 22.4% inulin, inulin composite protective agent, or skim milk composite protective agent showed different impacts on the energy metabolism, amino acid metabolism, and fatty acid metabolism in the fermentation of freeze-dried L. P dy-1. When the inulin content was increased from 10% to 22.4%, the differences in metabolic characteristics between freeze-dried bacteria and directly activated bacterial cells decreased. The metabolic characteristics of freeze-dried L. P dy-1 were closer to those of directly activated bacterial cells when using the inulin composite protective agent than when using the skim milk composite protective agent. Storage temperature had a significant effect on the metabolism of the freeze-dried bacteria; storage at -20 ℃ was more beneficial than storage at 4 ℃ to maintain the normal metabolism of L. P dy-1 during fermentation.
