In this work, we have investigated the synthesis and characterization of a proton conductor based on alginic acid and poly (1-vinylimidazole). The polymer network was obtained by mixing alginic acid and poly (1-vinylimidazole) at various stoichiometric ratios. The polymer electrolytes were characterized by elemental analysis and FT-IR spectroscopy. Invertase was entrapped in the polymer networks during complex formation. Additionally, the maximum reaction rate and Michaelis-Menten constant were investigated for the immobilized invertase. The temperature and pH optimization, operational stability and shelf life of the polymer network were examined. (C) 2008 Elsevier B.V. All rights reserved.