Preparation and properties of dextran sulfate-lysozyme conjugate.

The purpose of this research was to conjugate lysozyme with dextran sulfate (DS) under mild Maillard reaction conditions and to investigate the functional properties of the resulting conjugate. The covalent attachment of DS to lysozyme was confirmed by SDS-PAGE and cation-exchange chromatography. Lytic activity of the conjugated and uncongugated lysozyme toward Micrococcus lysodeikticus was 40 and 71% that of native lysozyme, respectively. The lysozyme-DS conjugate was highly soluble at alkaline pH values and different temperatures (25, 40, and 60 degrees C). Moreover, the modified lysozyme exhibited increased heat stability, with better emulsion activity and emulsion stability than those of unmodified proteins. Lysozyme-DS conjugate showed antibacterial activity and significantly inhibited growth of Staphylococcus aureus and Escherichia coli in a dose-dependent manner. Taken together, the result of this study demonstrated that conjugation might increase the applicability of lysozyme in different food products for improving functional properties.