Antibacterial activities of lactoperoxidase systems (LPS) modified by I- and IO3- anions

The antimicrobial activity due to the peroxidation of thiocyanate (SCN.) or iodide containing substrates (I- or IO3-) by lactoperoxidase was studied i n skim milk at 25 degreesC against Listeria (L.) monocytogenes ATCC 15313, Staphylococcus (S.) aureus CIP 7625, Pseudomonas (Ps.) fluorescens COP 6913 and Escherichia (E.) coli LMA1 and also at 15 degreesC for S. aureus. Exog enous H2O2 was supplied by glucose/glucose oxidase system. The lactoperoxid ase system (LPS) using SCN- was bacteriostatic for 48 h for the two Gram po sitive strains tested; it delayed but did not prevent the growth of the two Gram negative strains. The use of I- or IO3- instead of SCN- gave greater, permanent inhibition of Gram positive bacteria, particularly S. aureus at 25 and 15 degreesC. No significant antibacterial action was observed agains t the two Gram negative strains, Ps. fluorescens and E. coli.