Structure, functions and applications of lactoperoxidase in natural antimicrobial systems

Abstract

Lactoperoxidase (LPO) is quantitatively one of the most prominent enzymes in bovine milk; it catalyses the inactivation of many species of micro-organism in a lactoperoxidase system (LP-s). LP-s is harmless to mammalian cells and is also identified as an antimicrobial system in human saliva, milk and tears. The introduction of industrial processes for the recovery of LPO from milk and whey has renewed the interest in this enzyme as a natural antimicrobial tool for extending the shelf-life of milk and food products. During the last two decades the detailed chemistry of bovine LP-s has been elucidated. The major products responsible for the antimicrobial effects of LP-s have been characterized under conditions in which some micro-organisms will be killed and others are inhibited in their growth. Recent studies indicate that the field of actual and potential applications of these natural antimicrobial systems may be very broad. In this paper several aspects of LP-s are reviewed with respect to its application possibilities in food products. Starting with structure and properties of LPO, attention is focussed on the mechanism of its biological function in LP-s. Subsequently factors involved in the preservation of this function during food processing are discussed, and finally special attention is paid to the real and potential applications of LP-s in a number of food products. The general conclusion is that LP-s can be regarded as a naturally occurring antimicrobial system, which is a part of the biological defence against bacterial infections. In addition, other biological functions of LP-s are being observed in relation to human health and welfare. In vitro applications of LP-s are of increasing interest for preventing undue proliferation of contaminating micro-organisms in food products.