Lysozyme as a barrier to growth of Bacillus anthracis strain Sterne in liquid egg white, milk and beef

• Published in: Food microbiology Vol. 28; no. 6; pp. 1231 - 1234
• Main Authors: Sung, Kidon, Khan, Saeed A., Nawaz, Mohamed S., Cerniglia, Carl E., Tamplin, Mark L., Phillips, Robert W., Kelley, Lynda Collins
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2011; Elsevier
• Subjects: Animals; Bacillus; Bacillus anthracis; Bacillus anthracis - drug effects; Bacillus anthracis - growth & development; Bacillus anthracis - isolation & purification; Bacillus cereus; Bacillus pumilus; Bacillus subtilis; Beef; Biological and medical sciences; Cattle; Egg white; Egg White - microbiology; Food industries; Food microbiology; Food Preservation - methods; Food Preservatives - pharmacology; Fundamental and applied biological sciences. Psychology; Grounds; Heat treatment; Hot Temperature; Inactivation; Lysozyme; Meat - microbiology; Microbial Viability - drug effects; Milk; Milk - microbiology; Milk and cheese industries. Ice creams; Muramidase - pharmacology; Spore; Bacillus anthracis; Spore; Egg white; Inactivation; Lysozyme; Enzyme; Growth; Meat product; Dairy product; Bacillaceae; Spores; Strain; Glycosylases; Bacillales; Glycosidases; Bacillus; Egg product; Bacteria; Hydrolases; Liquid egg; Beef; Milk
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2011.03.002

In this study, we investigated the role of lysozyme on the viability of Bacillus cereus, Bacillus subtilis, Bacillus pumilus and Bacillus anthracis (Sterne) in egg white (EW), ground beef and milk. At 35 °C in EW, growth rates (GR) for B. cereus, B. subtilis, B. pumilus and B. anthracis were 0.005, −0.018, −0.028 and −0.029 OD600/h, respectively. Heat-treating EW at 55 and 60 °C reduced the inactivating effect of EW by 3.1 and 10.5-fold, respectively. Addition of lysozyme (2 mg/ml) to 60 °C-treated EW increased the inactivation rate 5.76-fold, indicating involvement of lysozyme in B. anthracis inactivation. B. anthracis inactivation was influenced by pH, as shown by a progressive increase in inactivation rate from 0.25 to −4.42 logs CFU/h over a pH range of 6.0–8.5. Adding 2 mg/ml lysozyme to milk and ground beef also suppressed the growth of B. anthracis 3.3 and 6.5-fold, respectively. These data indicate that lysozyme, as a natural component of EW or potential additive in other foods, could reduce biothreat risks presented by bioterror agents. ► Egg White contains high concentration of lysozyme and inactivated Bacillus anthracis (Sterne), B. pumilus and B. subtilis spores over a teperature range of 20–55°C. ► Inactivation of B. anthracis was influenced by pH and progressively increases from from 0.25''4.42 log CFU/h over a pH range of 6.0–8.5 at 35 °C. Moreover, inactivation rates at pH 7.0, were higher at 45 and 60 °C than at pH 8.5 (native pH of EW). ► Manipulation of temperature and pH could enhance the utility of lysozyme as a safe additive in different foods and could possibly lower thermal requirements for pasteurization. ► Addition of lysozyme in ground beef and milk suppressed the growth of B. anthracis. Lysozyme offers a limited but attractive possibility for potential applications in the food industry. ► Data from this research could be extended to other food matrices and used in developing value-added risk assessment models for food biosecurity.