Effect of cross-linking method on the activity of spray-dried chitosan microparticles with immobilized laccase

• Enzyme immobilization method by spray drying with in situ cross-linking was developed.
• Morphology and microstructure of chitosan microparticles were investigated.
• Laccase was successfully immobilized and its activity was assessed.
• Particles produced by in situ cross-linking have superior properties.

The effect of processing method on the properties of cross-linked chitosan microparticles and on the enzymatic activity of laccase immobilized in the particles has been investigated. Chitosan has been cross-linked by tri-polyphosphate (TPP) using two methods – the so called ex situ cross-linking whereby the solutions of chitosan, TPP and the enzyme have been pre-mixed and spray-dried by a standard two-fluid kinetic nozzle, and a novel in situ cross-linking method, whereby the solutions have been contacted at the tip of a three-fluid nozzle and cross-linking occurred within a drying droplet. The influence of the cross-linking method on the particle size and morphology, surface charge, and swelling ratio has been determined. The enzymatic activity of laccase toward the oxidation of a chromophore substrate (ABTS) has been systematically investigated and found to be superior in particles produced by the in situ cross-linking method.

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