Phage therapy by oral administration requires enhanced resistance of phages to the harsh gastric conditions. The aim of this work is the microencapsulation of phages in natural biopolymeric matrices as a protective barrier against the gastric environment. Alginate and pectin are used as base polymers. Further emulsification with oleic acid or coating with a different biopolymer is also studied. Emulsified pectin shows the maximum encapsulation efficiency and the highest protection against acidity, leaving more than 10³ active phages after 30 min exposure at pH¼1.6, and protects phage from pepsin activity (4.2mgmL⁻¹). Non-encapsulated phages are fully inactivated at pH¼1.6 or with pepsin (0.5mgmL⁻¹) after 10 min.Centro de Investigación y Desarrollo en Fermentaciones Industriales