The antimicrobial defence system of avian egg albumen.

Abstract

The components of avian eggs have attracted the attention of workers from all scientific fields but since the early descriptive investigations most studies have been concerned with the fundamental problems of protein chemistry, molecular biology, genetics etc., rather than the overall contributions of these proteins to the well being of the embryo. There is a large scattered literature on the occurrence, chemical and biological properties and phylogenetic traits of egg white proteins; this study brings together much of this literature and deals with the physico-chemical properties of these proteins with respect to their antimicrobial nature. It also presents a brief look at the consequences of iron deprivation in microbial metabolism, a situation that occurs through the metal chelating properties of albumen ovotransferrin. Studies were made on the antimicrobial mechanism of avian egg whites, with particular reference to hen egg albumen, and the major contributory factors identified. The respective influences of the two major biological proteins of egg albumen, lysozyme and ovotransferrin, were assessed using a wide range of micro-organisms including bacteria and yeast vegetative cells and bacterial endospores. In the case of bacteria, two mechanisms of inhibition by hen egg albumen, bacteriostasis and a bactericidal activity, were observed. Although iron deprivation was shown to be directly responsible for both of these mechanisms, a new interpretation of the importance of high alkaline pH in preventing microbial scavenging of this element is proposed. The importance of incubation temperature and pH on these mechanisms of inhibition were demonstrated. The antimicrobial system of avian egg albumen is discussed in relation to equivalent systems that occur in maranalian serum and milk. Finally a possible practical application of the antimicrobial mechanisms of avian egg albumen was demonstrated by inhibition of microbial growth in reconstituted dried baby feed and the relevance of this type of system in developing countries discussed.

Date of Award	1982
Original language	English
Awarding Institution	University of Bath