Encapsulation of bacteriophage T4 in mannitol-alginate dry macrospheres and survival in simulated gastrointestinal conditions

In recent years application of bacteriophages in the reduction of bacterial pathogens that may contaminate the food supply has become of growing interest. The aim of this study was to produce dried macrospheres ensuring viability of bacteriophages during exposure to adverse conditions of the digestive system after storage for an extended period of time. The viability of phages entrapped in mannitol-alginate wet and dried formulations was investigated for up to 4 weeks of storage at room temperature. Phage-loaded beads were exposed to an acidic environment (pH 2.5) of simulated gastric fluid and directly transferred to intestinal medium to dissolve. During the period from 1 to 4 weeks the survival of bacteriophage T4 in dried macrospheres under simulated gastrointestinal conditions revealed only a slight decrease and resulted in a final survival of 5.02 log10 pfu/ml. The results of this study show that the addition of 0.3 M mannitol may improve phage protection against gastrointestinal conditions and enable a large proportion of bacteriophage T4 to remain active. The potential of the developed technology can be considered in oral application of bacteriophages to reduce intestinal colonization of pathogenic bacteria via prolonged stability of phages in a dry state.