Effect of β-galactosidase immobilization on properties of chitosan/xanthan and xanthan/chitosan multilayers

Abstract

Polyelectrolyte multilayers (PEMs) deposited on non lyophilized and lyophilized polylactic acid (PDLA) substrates were investigated. The substrates were charged in a corona discharge. The charging of the substrates was carried out by means of a conventional corona triode system consisting of a corona electrode (needle), a grounded plate electrode and a grid placed between them. Positive or negative 5 kV voltage was applied to the corona electrode and 1 kV voltage of the same polarity as that of the needle - to the grid. The dependences of the normalized surface potential on the storage time for positively and negatively charged non lyophilized and lyophilized PDLA substrates were studied. The results obtained show that the values of the normalized surface potential of non lyophilized substrates decay faster than those of the lyophilized ones. For multilayer build-up layer-by-layer (LbL) deposition technique was used. The first built-up layer always possesses an electric charge opposite to that of the substrate. PEMs with different number of layers (4 or 8 layers) were obtained. In the polyelectrolyte multilayers obtained the enzyme β-galactosidase were immobilized. The enzyme activity of each multilayer configuration was measured. The experimental results show that, in case of enzyme immobilization in multilayer films with 8 layers the efficiency of immobilization is considerably better compared to ones with 4 polyelectrolyte layers.