Antibacterial Activity of the Lactoperoxidase System in Milk Against Pseudomonads and Other Gram-Negative Bacteria

Products of thiocyanate oxidation by lactoperoxidase inhibit gram-positive bacteria that produce peroxide. We found these products to be bactericidal for such gram-negative bacteria as Pseudomonas species and Escherichia coli, provided peroxide is supplied exogenously by glucose oxidase and glucose. By the use of immobilized glucose oxidase the bactericidal agent was shown to be dialyzable, destroyed by heat and counteracted, or destroyed by reducing agents. Because the system is active against a number of gram-negative bacteria isolated from milk, it may possibly be exploited to increase the keeping quality of raw milk.