Enzyme immobilization in latex dispersion coatings for active food packaging

Carboxylated styrene acrylate latex samples have been functionalized by the immobilization and entrapment of the enzyme glucose oxidase (GOx), which can be used as an oxygen scavenger in food packaging. GOx was covalently immobilized both on the surface of already formed films and on the latex particles in dispersion, as well as entrapped within the polymer matrix. In the latter two cases, polymer films were formed after the enzyme had been added to the latex dispersion. The storage stability of the enzyme and the influence of adding clay were also studied. For a given amount of enzyme, the enzyme immobilized on the film surface showed an enzyme activity about 10 times higher than that of the enzyme present within the polymer matrix. This is probably due to the diffusion limitations of the substrate in the polymer matrix. The films with the enzyme present within the polymer matrix, however, showed a higher total oxygen-removal capacity than films with the enzyme immobilized on the surface. Entrapped enzyme showed a slightly higher activity than enzyme immobilized in the dispersion due to the negative effect of the activating chemicals used during the immobilization and on conformational constraints upon covalent bonding. Low amounts of clay added to the dispersion decreased the enzyme activity, but with higher amounts of clay the enzyme activity increased, probably because of the increased porosity and thus higher substrate accessibility. The most suitable storage condition for all the enzyme-containing films was +8 degrees C, which is just above the glass transition temperature of the polymer used. Copyright (C) 2007 John Wiley & Sons, Ltd.