Hen egg white lysozyme is a naturally occurring protein found in the albumen of chicken eggs. This protein is a small enzyme. It is considered a globular basic protein with a high isoelectric point. Hen egg white is recognized as a particularly rich source of this enzyme, making up about 3.4% to 3.5% of the total proteins in the egg white.
The Science Behind Its Bacterial Defense
Hen egg white lysozyme functions as a lytic enzyme, meaning it causes cells to break open. It achieves its antibacterial effect by specifically targeting and hydrolyzing the peptidoglycan layer, a rigid structure forming the cell walls of many bacteria. Peptidoglycan is a polymer made of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) sugar units. Lysozyme breaks the β(1-4) glycosidic linkages between these NAM and NAG residues.
This enzymatic action weakens the bacterial cell wall. Once the cell wall is weakened, bacteria become susceptible to osmotic lysis, where they rupture and die due to the influx of water. Lysozyme is particularly effective against Gram-positive bacteria, which possess a thick peptidoglycan layer directly exposed to the environment. Gram-negative bacteria have an outer membrane that acts as an additional barrier, making them less susceptible to lysozyme, though some modified forms or combinations with other agents can broaden its spectrum.
Its Natural Role in Eggs
Hen egg white lysozyme serves as a component of the egg’s innate immune system. Its presence in the egg albumen provides a defense mechanism against bacterial contamination. The enzyme helps protect the developing chick embryo from potential infections that could hinder its growth. This protective function is particularly important as the egg provides a nutrient-rich environment that could otherwise support microbial growth. Lysozyme’s antimicrobial activity, along with other proteins in egg white like ovotransferrin, contributes to the natural preservation and safety of the egg.
Beyond the Shell: Its Many Uses
The unique properties of hen egg white lysozyme have led to its diverse applications across various industries, primarily due to its antimicrobial and enzymatic capabilities. In the food industry, it is widely utilized as a natural preservative, often listed as “generally recognized as safe” (GRAS). It helps extend the shelf life of products by inhibiting spoilage-causing bacteria, particularly Gram-positive strains.
Lysozyme is commonly added to certain cheeses to prevent “late blowing,” a defect caused by the growth of Clostridium tyrobutyricum, which produces gas and off-flavors during maturation. It also helps control the growth of lactic acid bacteria in beverages such as wine and beer, preventing unwanted fermentation or spoilage. Beyond these applications, it can be used in meat, fish, and their products, as well as in some fruit and vegetable preparations, either incorporated directly or applied as a surface coating.
In the pharmaceutical and medical fields, hen egg white lysozyme is explored for its broad biological activities, including antimicrobial, anti-inflammatory, and even potential antiviral properties. It can support existing immune defenses against bacterial infections, proving particularly beneficial in preventing bacterial diseases in infants. Research indicates its use in wound healing, for its anti-inflammatory effects on mucous membranes, and in regulating mucus secretion. Furthermore, it has been studied for its potential against certain viruses, including herpes, measles, and hepatitis, and has shown activity against HIV.