Biopolymer electrolytes based on dextran from Leuconostoc mesenteroides doped with ammonium nitrate (NH4NO3) are synthesized via a solution cast method. Fourier transform infrared analysis is used to determine the complexation between cation from the salt with functional groups of dextran. The ionic conductivity of undoped dextran film at room temperature is identified as (8.24 ± 0.31) � 10-11 S cm-1. A conductivity of (3.00 ± 1.60) � 10-5 S cm-1 is achieved with the inclusion of 20 wt NH4NO3 to the pure dextran film. The conductivity at a high temperature of the electrolyte obeys Arrhenius theory. Field emission scanning electron microscopy results show that the highest conducting sample has a porous surface. Results from the dielectric study show a non-Debye characteristic. © Indian Academy of Sciences.