Enzyme conjugation to the polysaccharide chitosan: smart biocatalysts and biocatalytic hydrogels

Laccase from Coriolopsis gallica was conjugated to the renewable biopolymer chitosan using carbodiimide chemistry. The laccase-chitosan conjugate was observed to offer three unique properties. First, the laccase-chitosan conjugate displayed pH-responsive behavior such that the conjugate was soluble and active under acidic conditions, but precipitated when the pH was raised toward neutrality. Second, the laccase-chitosan conjugate was more stable than free laccase at extreme pHs. At pH 1, the inactivation rate constant (k(in)) for the soluble laccase-chitosan conjugate was 20-fold less than that for free laccase. At pH 13, k(in) for the insoluble laccase-chitosan conjugate was nearly 3-fold less than that for free laccase. Finally, the laccase-chitosan conjugate could be cross-linked under mild conditions to create biocatalytic hydrogels. Potential benefits for enzyme-chitosan conjugates are discussed.