Lysozyme is an enzyme found in egg whites and other animal products that demonstrates antibacterial behavior by causing cell lysis in a number of bacterial species (Hughey and Johnson 1987). Most gram positive bacteria are known to be particularly sensitive to lysozyme, though there are also a number of gram-negative bacteria known to be susceptible to the enzyme (Masschalck and Michiels 2003). This enzyme is a peptidoglycan N-acetylmuramoylohydrolase that utilizes peptidoglycan as a substrate (Masschalck and Michiels 2003). Peptidoglycan is the primary component of a protective layer of cell walls in both gram positive and negative cells. Lysozyme will hydrolyze the peptidoglycan resulting in cell lysis (Masschalck and Michiels 2003). Gram negative bacteria have a complex outer membrane structure that frequently protects the peptidoglycan layer from lysozyme activity (Ellison and Giehl 1991). Not all gram-negative cells are completely resistant to lysozyme, and often the environment of the cells can be augmented to make them susceptible to cell lysis by lysozyme. Organisms likely produce these enzymes to protect from problematic bacteria. The application of lysozyme addition to control bacterial populations is especially valuable in the food and beverage industries.
Application in Wine Microbiology:
Lactic acid bacteria are common wine spoilage microorganisms. They also conduct a malo-lactic fermentation that many winemakers consider desirable; however, winemakers often work to prevent this fermentation to preserve a certain wine style. Lactic acid bacteria thrive in many post-fermentations wines, and it is useful to prevent unwanted growth of these organisms. Due to its antibacterial properties, lysozyme has been found to be effective in reducing the population of lactic acid bacteria (Gao et al. 2002). Studies of lysozyme activity show no effect on yeast cells and some reduction of acetic acid bacteria as well (Gao et al. 2002). Adding lysozyme to inhibit bacterial growth can be especially useful in wines with a high pH where SO2 will be less effective (Gao et al. 2002).
- Ellison R.T., Giehl T.J., Killing of Gram-negative Bacteria by Lactofernn and Lysozyme. 1991 J. Clin. Invest. 88: 1080-1091
- Gao Y.C., Zhang G., Krentz S., Darius S., Power J., Lagarde G., Inhibition of spoilage lactic acid bacteria by lysozyme during wine alcoholic fermentation. 2002 Australian Journal of Grape and Wine Research 8, 76–83
- Hughey V.L., Johnson E.A., Antimicrobial Activity of Lysozyme against Bacteria Involved in Food Spoilage and Food-Borne Disease 1987, Applied and Environmental Microbiology. 2165-2170
- Masschalck B., Michiels C. W., Antimicrobial Properties of Lysozyme in Relation to Foodborne Vegetative Bacteria. 2003, Critical Reviews in Microbiology 29(3): 191-214