Optimization of Lysozyme – Inulin Conjugation and Investigation on its Functional Properties

In recent years, several oconjugation protocols have been developed to improve the functional properties of the enzyme lysozyme. In this study, the optimum conditions of lysozyme – oxidized inulin conjugation and functional properties of the modified lysozyme were investigated. Initially, inulin (MW about 25 kDa) was oxidized by periodate to provide the reactive carbonyl groups  to attach to amino groups of lysozyme for Maillard reaction and was then conjugated to the enzyme at a molar ratio of oxidized inulin to enzyme of 5:1. A number of studies were conducted to investigate the optimization of lysozyme – Inulin conjugation consisting of different pH levels (3, 7, and 9), different temperatures (40, 60, and 80°C), and different reaction times. The degree of modification was determined by SDS-PAGE and sugar analysis of the product. The best condition for conjugation was determined to be 60°C at pH 7.0 for one week. The results showed that under these conditions, the inulin-lysozyme conjugate had 58% of the lytic activity of the native enzyme and had better emulsifying properties and heat stability than native lysozyme. Moreover, there was significantly higher protein solubility at pH 7.0 and 9.0 at different temperatures than heated lysozyme. Taken together, the results of this study indicated that lysozyme modification by oxidized inulin results in a new product with improved functional properties which may be employed for different industrial purposes.