Chitin/chitosan enzymatic functionalization

The enzymatic tools for functionalization of chitin/chitosan are selected on the basis of the chemical structure of these biopolymers (functional groups and targeted enzyme activities related) and include oxidases, e.g., tyrosinase, peroxidase, laccase and transferase (transglutaminase) types of enzymes. The same enzymatically assisted reactions could be further employed to crosslink the functionalized biomaterials in order to improve their exploitation characteristics, i.e., stability at use. 

Synthetic approaches for these materials are shown in Scheme 13. Introduction of maltoheptaose primer to chitosan by reductive amination was firstly carried out using NaBHaCN in a mixed solvent of aqueous acetic acid and methanol to produce maltoheptaose-grafted chitosan (39) [9]. The functionality of maltoheptaose to chitosan in 39 depended on reaction time. Maltoheptaose-grafted chitin (40) was synthesized by A-acetylation of 39 using acetic anhydride in a mixed solvent of aqueous acetic acid and methanol. Phosphorylase-catalyzed enzymatic polymerization of G-l-P from maltoheptaose in 39 and 40 was then performed to obtain amylose-grafted chitosan (41) and chitin (42), respectively. 

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