Emulsifying properties and bactericidal action of chitosan–lysozyme conjugates

Abstract

The solubility of chitosan was greatly improved by conjugation with lysozyme through Maillard-type protein–polysaccharide reaction. The emulsifying properties, especially emulsion stability, were improved by lysozyme–chitosan conjugation. The improvement in emulsifying properties was better in the conjugates of high molecular weight-type chitosan (HMC) than low molecular-type chitosan (LMC). The lysozyme–HMC conjugate has greatly improved emulsion stability at acidic pH. The conjugates have greatly enhanced bactericidal action against Escherichia coil K-12, a typical Gram-negative bacterium. Although the bactericidal activity of LMC was much lower than that of HMC, it was improved by conjugation with lysozyme. Thus, chitosan–lysozyme conjugate can be used as a new functional ingredient having excellent emulsifying properties and bactericidal action.