Chemical Modification of Lysozyme with Dextran by Using Maillard Reaction and Evaluating the Antimicrobial Properties of the Modified Enzyme

Lysozyme is a natural enzyme with positive antimicrobial activity against Gram Positive bacteria، but its action is limited on Gram Negative bacteria، which is assumed a restriction for its uses in industry. The purpose of this research was to glycosylate lysozyme with dextran through Maillard-based reaction and to study the antimicrobial characteristics of lysozyme-dextran conjugate. Glycosylation of lysozyme with dextran was performed using a 1:5 weight ratio of protein to dextran، incubated at 60 MC for one week under the relative humidity of 79%. For evaluating conjugation of dextran to lysozyme، SDS-PAGE electrophoresis was conducted. Gel filtration chromatography with sephadox G-100 was used for separation of conjugated enzyme. Lytic activity، free amino group and antimicrobial activity of the modified enzyme were evaluated. SDS-PAGE electrophoresis was used to follow the glycosylation process. Results indicated that 3. 7 moles of dextran were coupled to one mole of lysozyme. The lytic activity of the conjugate was about 62% of that of the native lysozyme. Evaluation of antimicrobial activity of the lysozymedextran conjugate، indicated the effectiveness of modified enzyme against E. coli and a progressive increase in antimicrobial activity with an increase in enzyme-conjugate concentration. The antimicrobial action of lysozyme on S. aureus was not improved by conjugation with dextran as compared with that of E. coli. These results might increase the application of lysozyme as a natural antimicrobial ingredient in different food systems.