Antibacterial Activity of Dextran-Conjugated Lysozyme against Escherichia coli and Staphylococcus aureus in Cheese Curd

• Published in: Journal of food protection Vol. 71; no. 2; pp. 411 - 415
• Main Authors: Amiri, S, Ramezani, R, Aminlari, M
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 01.02.2008
• Subjects: Anti-Infective Agents - pharmacology; antibacterial properties; bacterial contamination; Biological and medical sciences; Cheese - microbiology; cheesemaking; Chromatography, Gel; dextran; Dextrans - pharmacology; Electrophoresis, Polyacrylamide Gel; Enzymes, Immobilized; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - growth & development; food contamination; Food industries; Food microbiology; food pathogens; food preservation; Food Preservation - methods; food preservatives; food safety; Fundamental and applied biological sciences. Psychology; Glycosylation; Humans; lysozyme; Maillard reaction products; Microbial Sensitivity Tests; Micrococcus luteus; Micrococcus luteus - drug effects; Micrococcus luteus - growth & development; milk curds; Muramidase - pharmacology; Staphylococcus aureus; Staphylococcus aureus - drug effects; Staphylococcus aureus - growth & development; Enzyme; Escherichia coli; Glycosylases; Dextran; Cheese curd; Glycosidases; Bacteria; Hydrolases; Micrococcales; Micrococcaceae; Antibacterial agent; Lysozyme; Staphylococcus aureus; Enterobacteriaceae
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-71.2.411

The purposes of this research were to glycosylate lysozyme with dextran under Maillard reaction conditions and assess the antimicrobial characteristics of the lysozyme-dextran conjugate in a culture medium and cheese curd. Solutions containing lysozyme and dextran were incubated at 60 degrees C and at 79% relative humidity. Gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to follow the glycosylation process. Under optimum conditions 3.7 mol of dextran were coupled to 1 mol of lysozyme. Lytic activity of the conjugate against the cell wall of Micrococcus luteus was about 62% of that of native lysozyme. Evaluation of the lysozyme-dextran conjugate against test microorganisms (Staphylococcus aureus and Escherichia coli) in culture media indicated a progressive increase in antimicrobial activity, with an increase in enzyme-conjugate concentration. The lysozyme-dextran conjugate was also effective against E. coli in a natural food system, as it reduced the bacterial count by 3 log in cheese curd after 40 days of storage. Unlike E. coli, the antimicrobial action of lysozyme against S. aureus was not improved by conjugation with dextran in both in vitro and in vivo tests. Antimicrobial activity of the lysozyme-dextran conjugate against gram-negative bacteria is probably related to the remaining lytic activity as well as the excellent surfactant properties of the lysozyme-dextran conjugate. These results might increase the applicability of lysozyme as a natural antimicrobial ingredient in different food products.