Production and properties of tragacanthin-conjugated lysozyme as a new multifunctional biopolymer

In this communication we describe preparation and characterization of an enzyme-biopolymer conjugate composed of water-soluble part of gum tragacanth and chicken egg white lysozyme (LZM) under mild Maillard reaction conditions. SDS-PAGE together with FT-IR spectroscopy revealed that Maillard reactions occurred between LZM and tragacanthin (TRG). Under optimum conditions (pH = 8.5, 60 degrees C, RH = 79%, 8 days), approximately 2 TRG molecules were attached to one LZM molecule. DSC analysis showed that conjugation with TRG increased denaturation temperature by 6.35 degrees C. The resulting conjugates were characterized using scanning electron microscopy. The modified enzyme activity retained 77% of the original enzymatic activity after 8 days. TRG-conjugated LZM exhibited improved solubility and emulsion properties as compared with the native LZM. In addition, a significant increase in foam capacity and stability of LZM-TRG conjugate was detected. Conjugate with TRG significantly improved the inhibitory effect of LZM on the growth of Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhi in a dose dependent manner such that at 4000 mu g/ml, LZM-TRG conjugate inhibited S. aureus, Bacillus cereus, Escherichia coli and Salmonella typhi by 90%, 80%, 50% and 40%, respectively. Taken together these results suggest that the functional properties and antimicrobial activities of LZM can be improved by conjugation with TRG. The conjugation might expand the applications of LZM as a multifunctional ingredient in food and pharmaceutical industries.