Determining the Role of UTP-Glucose-1-Phosphate Uridylyltransferase (GalU) in Improving the Resistance of NCFM to Freeze-Drying.

NCFM is widely used in the fermentation industry; using it as a freeze-dried powder can greatly reduce the costs associated with packaging and transportation, and even prolong the storage period. Previously published research has reported that the expression of (EC: 2.7.7.9) is significantly increased as a result of freezing and drying. Herein, we aimed to explore how plays an important role in improving the resistance of NCFM to freeze-drying. For this study, was first knocked out and then re-expressed in NCFM to functionally characterize its role in the pertinent metabolic pathways. The knockout strain Δ showed lactose/galactose deficiency and displayed irregular cell morphology, shortened cell length, thin and rough capsules, and abnormal cell division, and the progeny could not be separated. In the re-expression strain p, these inhibited pathways were restored; moreover, the p cells showed a strengthened cell wall and capsule, which enhanced their resistance to adverse environments. The p cells showed GalU activity that was 229% higher than that shown by the wild-type strain, and the freeze-drying survival rate was 84%, this being 4.7 times higher than that of the wild-type strain. To summarize, expression of the gene can significantly enhance gene expression in galactose metabolic pathway and make the strain form a stronger cell wall and cell capsule and enhance the resistance of the bacteria to an adverse external environment, to improve the freeze-drying survival rate of NCFM.