Preparation and application of Escherichia coli O157:H7 phage cocktail spray drying microcapsule

Abstract:

[Objective] To improve the storage stability of the phage at room temperature, solve the problem of inactivation of phage cocktail in vivo, and provide references for the effective treatment of gastrointestinal diseases by phages. [Methods] This study prepared phage cocktail microsphere powder by spray drying technology. The optimal preparation conditions were determined by single factor experiment and orthogonal experiment. The characteristics were studied, and the stability of the phage was compared with that of free phage at room temperature and in vivo was compared. Gastrointestinal diseases caused by Escherichia coli O157:H7 were treated by oral administration. [Results] In this study, a combination of trehalose and leucine was used to prepare a thermally stable phage cocktail microsphere powder. The results showed that the optimal mass ratio of trehalose and leucine was 9:1, the optimal speed of wriggling pump was 7.5 mL/min, the optimal trehalose concentration was 2%, the optimal inlet temperature was 130 ℃, and the optimal volume ratio of the phage cocktail suspension to the protectant solution was 1:50. Under the optimal conditions above, the titer loss was the lowest, only decreased by (0.623±0.235) log₁₀ PFU/g. After 6 months of storage at room temperature, the titer loss of the phage cocktail microsphere powder was only (0.862±0.082) log₁₀ PFU/g, which had longer storage stability than the free phage, and the stability in vivo and therapeutic effect were much better than the free phage. [Conclusion] Studies have shown that the spray drying method and suitable protective agent formula can be used to prepare phage cocktail dry powder with biological activity and thermal stability, which can extend retention time, facilitating the transportation under normal temperature conditions. This provides references for the transformation of phage preparations from the laboratory to the industrial large-scale production. Moreover, the phage microsphere powder shows an excellent ability to remove E. coli in the intestinal tract with a high speed, indicating its potential as an orally therapeutic agent in vivo.