The invention proposes a biological protection membrane which is mounted, in a device for dispensing liquid from a sterile packaging bottle, across a fluid-circulation duct, in the path of the liquid extracted from the bottle and the outside air which is drawn into the bottle. The membrane (7) is made partially of a hydrophilic material and partially of a hydrophobic material. Both the hydrophobic portion (23) and the hydrophilic portion (22) are made from a polymer base, laden in the body thereof with a biocidal agent that is active in the destruction of bacteria by the ionic oxidation effect. The circulation of fluids through the membrane (7) is organised so as to promote the ionic action on the flow of outside air in the hydrophobic material, and to drive the ionically charged active agent by the liquid passing through the membrane in the hydrophilic portion thereof. A porous buffer (8), inserted in the path of the fluids on the inside of the membrane, collects the active agent extracted from the membrane by the remaining liquid not dispensed, passing through the membrane from the outside towards the inside.
