Abstract:

As a biodegradable macromolecule，chitosan functions with unique characteristics. However，limited by its solubility and other factors，chemical method is used to improve chitosan’s properties. As chemical modifications can cause environmental pollution，need more reactive steps and suffer from poor specificity，biological modification methods get more attention. As a dual-function biological catalyst，tyrosinase catalyzes two different oxygen-dependent reactions that occur consecutively，o-hydroxylation of monophenols to yield o-diphenols（cresolase activity）and the subsequent oxidation of o-diphenols to o-quinones（catecholase activity）. Tyrosinase specificly grafts phenolic compounds to chitosan to improve its solubility. Tyrosinase oxides o-diphenols of o-quinone and plays the role of cross-linking agent to reinforce the tensile properties of chitosan membrane. Tyrosinase oxides protein tyrosine residues to form chitosan conjugates. With further research，tyrosinase’s application on chitosan biological modification will be more extensive.