application of alternative food-preservation - Bentham Science

58 Application of Alternative Food-Preservation Technologies to Enhance Food Safety & Stability, 2010, 58-82
Enzymes and Enzymatic Systems as Natural Antimicrobials
Daniela D’Amato, Daniela Campaniello and Milena Sinigaglia*
Department of Food Science, Faculty of Agricultural Science, University of Foggia, Italy
Antonio Bevilacqua, Maria Rosaria Corbo and Milena Sinigaglia (Eds)
All rights reserved - © 2010 Bentham Science Publishers Ltd.
CHAPTER 5
Abstract: Lysozyme is a hydrolytic enzyme which has been purified from cells, secretions and tissues of
virtually all living organisms and viruses. Lysozyme has been shown to have antimicrobial activities towards
bacteria, fungi, protozoan and viruses; moreover, it is essentially known for its antibacterial activity and has
been used in food preservation. Lysozyme is currently used as a preservative in many foods, such as cheese,
fish, meat, fruit, vegetables and wine.
Lactoferrin is a globular multifunctional protein with antimicrobial activity. It is produced by mucosal
epithelial cells in various mammalian species. It is found in mucosal surfaces and in biological fluids,
including milk and saliva. It possesses a strong antimicrobial activity against a broad spectrum of bacteria,
fungi, yeasts, viruses and parasites. Lactoferrin is used in a wide range of products including infant formulae,
sport and functional foods.
The lactoperoxidase system (LPS) consists of three components: enzyme lactoperoxidase, thiocyanate and
hydrogen peroxide. LPS exerts both bacteriostatic and/or bactericidal activity; therefore, its use in dairy
industry to preserve raw milk quality or to extend the shelf life of pasteurized milk has been extensively
proposed in the past. LPS has also been used the stabilization cream, cheese, liquid whole eggs, ice cream,
infant formula and for the preservation of tomato juice, mangoes and chicken.
Key-concepts: Lysozyme, Lactoferrin, Lactoperoxidase, Mode of action and application in foods.
LYSOZYME: STRUCTURE AND PROPERTIES
LYSOZYME
Lysozyme is a hydrolytic enzyme which has been purified from cells, secretions and tissues of virtually all living
organisms and viruses. It is well known as an antimicrobial protein, used as a natural food preservative.
Lysozyme is a 129-amino acid protein with a molecular weight of approximately 14.7 kDa, and with hydrolytic
activity against ß (1–4) glycosidic linkages between N-acetylmuramic acid and N-acetylglucosamine in bacterial
peptidoglycan [1]. In addition, it has been reported to have an antibacterial activity that is independent of its
enzymatic activity [2]. Lysozyme was discovered in 1922 by Flemming in human nasal secretion and
subsequently purified from various plant, animal, microbial (bacteria, virus and fungi) materials [3-5]. It is
naturally present in many foods such as egg white (with a concentration ranging between 3.2 and 5.8 mg/ml),
cow milk (ca. 0.13 mg/ml) and human colostrum (ca. 65 mg/ml) but also in several plants, such as cauliflower
(ca. 27.6 mg/ml) and cabbage (ca. 2.3 mg/ml) [6], and widely distributed in various biological fluids and tissues
including plant, bacteria, and animal secretions, tears, saliva, respiratory and cervical secretions, and secreted by
polymorphonuclear leukocytes [7].
Lysozyme constitutes a natural defence against bacterial pathogens. Many bacteriophages also produce lysozyme
that locally hydrolyses the peptidoglycan to facilitate penetration of the phage injection apparatus, or that
induces cell lysis at the end of the phage replication cycle.
Lysozyme has an extremely high isoelectric point (>10) and consequently is highly cationic at neutral or acid
pH. In solution, it is relatively stable at pH 3-4, but when pH increases its stability decreases.
Several classes of lysozyme have been defined on the basis of the wide variability in origin, and structural,
antigenic, chemical and enzymatic properties of the molecules. In Table 1 some of the different types of
lysozyme are reported. The most studied and the best known is the conventional or chicken-type (i.e. clysozyme)
with the lysozyme derived from the egg white of domestic chicken (Gallus gallus) as the prototype
[8]. Although, c-lysozyme is typically found in the egg white of birds, it was also purified from various tissues
and secretions of mammals.
*Address correspondence to this author Milena Sinigaglia at: Department of Food Science, Faculty of Agricultural Science, University
of Foggia, Italy; E-mail: m.sinigaglia@unifg.it